'''''[-This page is for the Half-Life series as a whole. If you're looking for the first video game in the series with the same name, [[VideoGame/HalfLife1 please click here.]]-]'''''

->''You can't even walk down the street of your own planet anymore! I remember the good old days when I didn't have to bring a gun to work, my coworkers weren't space bugs, I had a salary, I wasn't wanted by the government...''\\
[spots an alien]\\
''Then '''you''' happened!''
-->--'''Gordon Freeman''', ''Machinima/FreemansMind''

''Half-Life'' is a series of {{First Person Shooter}}s created by Washington-based developer team Creator/{{Valve|Software}}. The series follow the life of physicist Gordon Freeman, a bearded, bespectacled HeroicMime who works in the Anomalous Materials laboratory at the vast Black Mesa Research Facility, a [[ElaborateUnderGroundBase top-secret complex]] in the middle of the New Mexico desert.

!!The games composing the series are the following:
* ''VideoGame/HalfLife1''
** ''Half-Life: Opposing Force''
** ''Half-Life: Blue Shift''
** ''Half-Life: Decay''
* ''VideoGame/HalfLife2''
** ''Half-Life 2: Episode 1''
** ''Half-Life 2: Episode 2''

''Videogame/{{Portal}}'' is [[GaidenGame a side story]] to the series, whose plot has evolved almost completely separately given that it takes place entirely inside the Aperture Science complex, established in-game as a rival to the Black Mesa Research Facility. Because of its enormous popularity, it seems to have overtaken the ''Half-Life'' series as the focus of Valve's attention for now, projects like ''VideoGame/TeamFortress2'' and ''VideoGame/Left4Dead'' (obviously not set in the main ''Half-Life'' universe) notwithstanding.

Finally, there is ''VideoGame/BlackMesa'', a free FanRemake of the original Half-Life using the Source engine used for Valve's newer games. [[ShownTheirWork It's very well done]], and [[ApprovalOfGod Valve itself has expressed admiration for it]].

The series now has a Recap page covering all games as well as both ''{{Videogame/Portal}}'' games. It is currently a black hole of red links and is in dire need of WikiMagic.

'''This page applies for the series as a whole. Please add any examples from an individual game to their dedicated pages.'''

!!The ''Half-Life'' series contains examples of:


* AbandonedMine: Towards the end of Ravenholm and much of the early setting in Episode 2.
* AbandonedHospital: One of the settings in Episode One, which appears to have been taken over by the Combine. The impending city-sized explosion left it in the process of being abandoned ''again''
* AbnormalAmmo:
** The Gravity Gun easily invokes this trope, given that you can pick up and launch almost anything with it. When supercharged by dark energy, it can even pick up people, which kills them instantly.
** The Hive Hand, which generates and shoots alien bees.
** Half-Life 2's Crossbow fires lengths of glowing hot rebar.
** The first game has two weapons that use depleted uranium for ammunition.
* AbortedArc: Shephard and his purpose to The G-Man have not been mentioned outside of Opposing Force.
* AccentUponTheWrongSyllable: The G-Man speaks with this.
* ActionGirl: Alyx and the female rebels, who fight just as well and hard as the males.
* AirVentPassageway: This game is famous for its heavy use of this.
* AliensAndMonsters: Primarily featured in the first game; by the second, one of the alien species had joined our side, all the others except for the headcrabs have mysteriously vanished, and most of the enemies are human cops and transhuman soldiers working for the unseen Combine, an interstellar and apparently multidimensional empire bent on universal conquest.
* AllDesertsHaveCacti: The original ''VideoGame/HalfLife'' has a few saguaro cacti in the outdoor areas... despite being located in New Mexico. (While New Mexico has cacti, it ''doesn't'' have saguaros.)
* AllThereInTheManual: Averted, as part of the series' unique storytelling strategy. Despite you having been missing and in stasis for several years between parts 1 and 2, at no point does anyone explain to you what the hell happened during that time, nor does Gordon ever ask to be filled in. Unless you look at every newspaper clipping along the way, you can complete the entire game without any knowledge of the "Seven Hour War" or of what the Combine really is. Also, the only character that gives any real exposition is very easy to miss if you don't know where to look for him. If you have a lot of free time and possess an insane measure of dedication, you can construct a reasonably coherent picture - read [[http://www.members.shaw.ca/halflifestory/timeline.htm this timeline]] to get the most probable theory.
* AlternateCharacterInterpretation - ''In-universe''. While it's implied quite a few Marines are having second thoughts of shooting civilians to cover-up the Black Mesa incident, everyone in the HECU wants a piece of Gordon Freeman - scuttlebutt had him killing a few Marines in cold blood, not to mention they believe him to be the one responsible for the whole mess (and not just the guy who pushed the crystal in). [[spoiler:Given that G-Man, the one who did initiate the resonance cascade, later hires Freeman as his elite agent, they aren't that far off. It's just that Gordon is an unwilling (as far as we can tell) agent of the G-Man.]]
* AmbiguousRobots: Pretty much everything you fight in the ''Half-Life 2'' series (less headcrabs, zombies and antlions) is ambiguously cyborg in nature. The flying synths and the Striders are probably the most ambiguously robotic.
* AnotherDimension: Xen, and the Combine as an inter-dimensional empire.
* ArbitraryGunPower: In both games, the 9mm pistol is the weakest weapon. The revolver, on the other hand, is the strongest firearm, and both are beaten by the crossbow.
* ArcWords: "Unforeseen Consequences", which does quintuple duty as {{Foreshadowing}}, LeaningOnTheFourthWall, CallBack and WhamLine all at once.
* ArmiesAreEvil:
** The shadowy Hazardous Environment Combat Unit who serves under the US military and who, thanks to their orders to kill the personnel of Black Mesa, is one of the main threats in Half-Life.
** HECU gets their own [[ArmiesAreEvil Army]] in the even more shadowy Black Ops unit, who apparently goes even higher in command. Like the HECU, they're also there to stop the alien infestation after the HECU fails, with predictable results.
* ArtificialBrilliance: ''Half-Life'' was widely praised for the A.I. of its human Marine enemies, who were the first FPS enemies to work in squads and use complex tactical behaviors and movement patterns instead of simply charging in a straight line at the player...
* ArtificialStupidity: Especially true of the HECU marines, who, despite showing off some pretty sophisticated AI behavior for the time, will break instantly as soon as there's more than one player, since it was heavily dependent on rigid scripting. Furthermore, while they are programmed to place grenades on the ground to cover their retreats, you can shoot them in the act, breaking that bit of programming and causing them to shoot back instead, instantly forgetting all about the armed grenade there is ''right beneath their own feet''.
** HECU marines will also lay down laser trip mines on occasion to block off routes for the player. However, sometimes they'll place one in the only exit out of an area they're in and will run right into their own trip mines to search for the player if they cannot attack the player from their current position.
** Civil Protection officers will take cover behind explosive barrels, stand on the most rickety and fragile structures they can, and rappel in front of a moving vehicle only to get immediately run over. Most of this is scripted, but they're still not very smart otherwise.
** The HECU also had a hilarious habit of mixing up their reactions to grenades. When a Marine shouts to his comrades he's throwing or putting down a grenade, they normally crouch and cover their head, while he runs away from the grenade. Sometimes they get confused, and the Marine will put down the grenade at his feet, then crouch beside it and cover his head, and of course be blown to bits. Easy kill.
** Friendly [=NPCs=] in [=HL1=] and Opposing Force both had a tendency to shoot you if you happened to be between them and an enemy.
* {{Autodoc}}: Both first aid stations, which heal you, and similar looking HEV stations, which recharge your HEV suit.
* {{Autosave}}: The games autosave in certain places or intervals. If you want to to back before an autosave, you can always load the previous save file.
* BackdoorPilot: ''VideoGame/{{Portal}}'' was developed by a small team with a limited budget who wrote the game into the ''Half-Life'' continuity so they could re-use those games' assets. Now that it's a standalone franchise.
* BadassBookworm: Gordon, duh. Dr. Breen himself is perplexed, and had this to say on the matter:
--> "How could one man have slipped through [[FacelessGoons your]] forces' fingers time and time again? How is it possible? This is not some agent provocateur or highly trained assassin we are discussing. Gordon Freeman is a theoretical physicist who had hardly earned the distinction of his Ph.D. at the time of the Black Mesa Incident. I have good reason to believe that in the intervening years, he was in a state that precluded further development of covert skills. The man you have consistently failed to slow, let alone capture, is by all standards simply that -- ''an ordinary man''."
* BadassPreacher: Father Grigori.
* BagOfSpilling:
** More or less justified in every case: The G-Man took away all your weapons at the end of Half-Life[[labelnote:*]]He said most of them were government property[[/labelnote]], and having your HEV suit would make it harder to get through the train station. In Episode One, you had already been stripped of everything but the gravity gun and your HEV suit very late in ''Half-Life 2''. In Episode Two, all of your weapons had been thrown from the train when it derailed, and only the gravity gun was close enough for Alyx to find.
** A variation/inversion of this occurs with the games' chapter systems. You can start a brand new game at the beginning of any chapter you've already reached; the game equips you with every weapon available at that point and a reasonable amount of ammo, plus full health and some HEV Suit Power, regardless of whether you have ever made it that far without running out of something or running low on health.
* BigBad: The Nihilanth is this in the first game, with the Combine as this in the second and are revealed to have been a GreaterScopeVillain in the first.
%%* BilingualBonus
%%* BilingualDialogue
%%* BlockPuzzle
* BodyHorror: Headcrab zombies, which tore open the chest of the victim, and in the first game, fused the crab to the victim's head. In the second, it tore out their eyeballs and left them screaming for death. In Opposing Force, a headcrab zombie will mutate into a bigger, nastier, pile of flesh with green lumps everywhere and horrendous claws.
** Stalkers, which are the emaciated, amputated, barely-sentient corpses of prisoners with rudimentary cybernetic implants drilled into their bodies.
** Gordon would find random burnt corpses, or the disfigured bodies of what used to be those who were taken in by Civil Protection.
* BolivianArmyEnding:
** If Gordon rejects the G-Man's offer at the end of ''Half-Life,'' he is teleported unarmed into a room full of alien grunts. The game doesn't even show what happens, simply fading to black and showing "Subject: Gordon Freeman. Status: Terminated. Postmortem: Refused offer of employment."
---> "No regrets, Mr. Freeman...[[DummiedOut but there are a few survivors of your personal holocaust, who would like the chance to meet the man responsible for the total annihilation of their race.]]"
** ''Half-Life: Uplink'' ends with Gordon trapped by a Gargantua with no real means of defeating it.
* BondVillainStupidity: Two marines, instead of dragging you to your interrogation and execution, toss you into a trash compactor. Filled with crates. And another crowbar sitting at the top.
* BookEnds:
** The first game began and ended in a tram. Also interesting is that this seems to slightly carry over to the next game, where the player starts off in a train and also ends the game on a train, albeit the G-Man's metaphysical one. Episode One also ends with Gordon on a train, and Episode Two starts with you on a ''crashed'' train.
** Opposing Force keeps the tradition, though the tram in this case is a V-22 Osprey.
* BoringButPractical: In the first game, the most useful weapon was probably the humble Glock 17, the first gun you found, due to its common ammo and its amazing accuracy. It's almost a game breaker because no enemy can touch you at the range you can hit them with the pistol. The second game had the MP7, which was really useful for dispatching Civil Protection officers and Antlions. It's fairly inaccurate and weak, but ammo is literally everywhere and it fires extremely fast. It becomes next to useless after you get your hands on the (also boring but practical) [=AR2=] and SPAS-12, though.
* BossArenaIdiocy: The Nihilanth is invincible by drawing upon the power of (and expending) energy orbs floating around its head, which get replenished by easily destroyable crystals on the walls of its chamber. Once the crystals are gone, the orbs eventually run out and the Nihilanth is toast.
* BrokenBridge: Dozens of them. {{Lampshaded}} in Episode 2 by the Vortigaunt, who declares, "Pity the generator that requires a Vortigaunt to activate it."
* BrainsAndBrawn: ''"With my brains and your brawn, we'll make an excellent team!"'' Except Gordon usually provides both.
* BribingYourWayToVictory: Not ''Half-Life'' itself, but mods are free to implement this, such as Sven Co-op.
* BrickJoke:
** In the very first game, you can repeatedly mess with a microwave until someone's lunch explodes and you get a WhatTheHellPlayer from a nearby scientist. The brick doesn't come crashing down for 3 sequels and 10 real-life years until you meet Dr. Magnusson, the owner of that lunch, in Episode Two. He's still annoyed about it.
** A similar example, though with not as many years between: If you try to talk to security guards (the basis of the character Barney Calhoun) before the resonance cascade, one of their random lines is, "Hey, catch me later, I'll buy you a beer." In Half-Life 2, Barney's first line upon revealing his identity to Gordon is, "About that beer I owed ya."
** During their first meeting in the second game, Dr. Vance lampshades this, saying "The last time I saw you, I sent you to get help after the resonance cascade. I didn't think it would take you this long to get back to me!" referencing a conversation with a (then-generic) dark-skinned scientist right after the cascade.
** The major WhamLine in Episode 2, which is even more obscure because [[spoiler:the words are the name of a level in the first game, that only appears as a caption and never spoken by anyone]].
* CavalryBetrayal: The scientists and guards Gordon comes across in the first few hours after the resonance cascade will enthusiastically tell you that the US military have called in via radio and told that a team is under way to Black Mesa to kill the aliens and rescue the personnel of the facility. While the first part of the message is true, the team's orders have been changed (or always were) to terminate the personnel because of their status as witnesses.
* ChargedAttack: The Gauss Gun from ''Half-Life'', the wrench from ''Opposing Force'', and the mounted Tau Cannon on the buggy in ''Half-Life 2''. The pistol in [=HL2=] could originally do this but it was removed in a later patch.
* ChargeMeter: At least, for the flashlight.
** And for ''Half-Life 2'' and later, suit power (which included the flashlight until ''Episode Two'').
%%* CharlesAtlasSuperpower: Gordon, thanks to his HEV Suit.
* TheChessmaster: "I do apologize for what must seem to you an arbitrary imposition, Dr. Freeman. I trust it will all make sense to you in the course of... well... I'm really not at liberty to say. In the meantime... this is where I get off."
** The G-Man will save people and provide them with information, but also interfere with their plan to move them into situations where [[UnwittingPawn everything they will do for their own gain will also advance his own plan]]. He isn't even trying to hide it.
* ClassicCheatCode:
** God mode and such.
** Noclip and Impulse 101 are at the top of about 95% of the console code lists. If you have ever used the console, you probably use Noclip and Impulse 101 the most. By extension, sv_cheats 1 is well known, since it is needed to enable those two.
* ClothesMakeTheSuperman: Gordon's ubiquitous HEV suit. It's the only reason he was able to survive the resonance cascade at ground zero and kill the Nihilanth: he's the only survivor wearing (and trained in using) an HEV suit.
* ClimaxBoss: The Gonarch in ''Half-Life 1''. The WolfpackBoss fight with a group of Striders in ''Half-Life 2''.
* CombatMedic: The second game has them as resistance fighting the Combine. They'll charge in and gun down enemies with an [=MP5=] before running to Gordon to patch him up.
* CosmicHorrorStory: As the games progress, one can't help but get this vibe with the series. Especially with the presence of the Combine, a force that comes off as some never ending horror series of atrocity after atrocity. Then there's the appearance of guys like the Headcrabs and Antlions....
%%* ConspicuouslySelectivePerception
* CopyProtection: Steam, which one must have to activate even retail copies of any Valve game since ''Half-Life 2''.
* CorridorCubbyholeRun: At the exit to the Ravenholm mines, there's a buzzsaw trap that zooms back and forth along a track, shredding all the zombies in your way. It will also shred ''you'' or run you over if you don't stay out of its way.
* CorruptCorporateExecutive: Dr. Breen, head administrator of Black Mesa. The research conducted under his administration would not hold up to any kind of ethical standards. May or may not have [[EvilPlan set up]] the entire Black Mesa Incident in order to [[spoiler:be appointed head administrator of ''the entire human race''.]]
** The G-Man also seems to fill this role. He ''is'' always wearing a snappy business suit, after all.
* CrapsackWorld: The entire planet Earth. Even if you do save it from the Combine, mankind's probably going to spend the rest of its existence fighting off Antlions and all the other alien monstrosities that call it home now. Ironically, the Combine seemed to be doing a pretty good job staving off those monstrosities. Making them something of a collective LoadBearingBoss.
* CrateExpectations: Half-Life series has plenty of them.
* CreepyCockroach: Roaches (possibly alien, as their body shape is closer to that of a bug than a roach) appear throughout the original game. Surprisingly absent in the sequels.
* CriticalExistenceFailure
** Justified in that the suit has built in medical tech and movement assisting features. Even when the reactive armour is inactive, the suit can absorb damage that should otherwise cripple or even kill the wearer, while the suit's medical systems administer medicine (refilled from health containers or stations) to take care of whatever manages to leak through. This is evidenced in-game by the manner in which the suit responds to the damage Gordon takes, such as applying morphine to dull the pain of a bone-breaking jump.
* CrowbarCombatant: Gordon Freeman can wield a crowbar for most of the series and each game in the main series has it as a weapon (to the point where it is one of the most iconic examples of this trope). It also appears as a usable weapon in the ExpansionPack ''Blue Shift'', for Barney Calhoun.
%% The 'crowning' stuff has its own page
* DamageSpongeBoss: Most bosses in the Half-Life series are either a PuzzleBoss or can be defeated very quickly with a powerful weapon. The Gonarch, however, has no real other strategy to it than "circle strafe while firing all weapons at testicle, avoid white acid, run after it, repeat". It also has invincibility frames.
* DeadlyRotaryFan: Several times in the first game and at least once in ''VideoGame/HalfLife2'', you have to pass through, or by, an active fan. Touching the blades means [[OneHitKill instant death]].
* DeliciousDistraction: Bullsquids can be distracted with meat strung up in the meat locker you first find them in.
* DieChairDie: Crowbar, meet crate. Somewhat silly, since a crowbar is supposedly designed for ''opening'' crates, but the only way to get at the ammo inside is to smash 'em.
* DiegeticInterface: Would normally be {{Justified|Trope}} by Gordon's PoweredArmor, either through his glasses[[labelnote:*]]since he never wears the suit's helmet[[/labelnote]] or some other way.
%%* DiscardAndDraw
* DoNotRunWithAGun: Gordon, Adrian, and Barney all run quite fast. Averted in [=HL2=], where the only way to go faster is to sprint, which uses your energy.
* DoorToBefore: Quite a few appear in the main game, largely averted in the second.
* DoubleMeaningTitle: ''Blue Shift'' is a physics term, and a security guard on shift. Not to mention ''Opposing Force'', which is an obvious reference to both Newton's Laws and the fact that the protagonist is one of the antagonistic HECU members from the original game.
* DrillSergeantNasty: "Keep your PCV fully charged and I guarantee it will save your life! Step onto that square!" <player is blasted with a shotgun> "As you may have noticed, YOU ARE NOT DEAD."
* DropPod: The Combine Headcrab Canisters.
* EarnYourHappyEnding: Barney goes through a ''lot'' to have the sole happy ending of a ''Half-Life'' game.
* EldritchAbomination:
** In the first game, the aliens (and Xen in particular) sure seem this way.
*** The Nihilanth, a gigantic levitating amputated fetus.
** The G-Man ''might'' be this, or more of a HumanoidAbomination.
*** This is assuming that is even his real form!
** The Advisors, the enigmatic, grub-like psychic Overlords of the Combine Regime on earth.
* EleventhHourSuperpower: The Super Gravity Gun, which appears in the final chapters of the second game and the first chapters of ''Episode One'', both times within the Citadel. It has enormous range, can grab people and Dark Energy balls as well as inanimate objects, and will always deliver a OneHitKill.
* EnemyChatter: The HECU often communicate with each other and taunt Gordon, impressive for the late nineties. In addition, so do the Combine troops, which also have a city-wide Dispatch for the Metrocops. The Black Ops were considerably more silent, and much harder to predict, as a result.
* EnergyBall: From what we can tell, a ball of [[ShownTheirWork Dark Energy]] ''might'' behave like that.
* EscapeSequence: A few times in Point Insertion, Route Kanal and Water Hazard.
* EscortMission:
** Several times in the first game you need to escort a scientist from a hiding place to a door. Barney must also escort a scientist safely to escape Black Mesa in his expansion pack. However, these escort missions aren't too much of a pain, as you can tell them to stay put while you clear out the area ahead, and they will. That, and most of the "escort missions" in the game are optional.
** Averted in ''Half-Life 2''. Barney and Alyx both carry automatic weapons and have rapidly regenerating health, while Grigori gets a [[{{BFG}} double-barreled rifle]] that can instantly kill most enemies and is almost perfectly accurate.
** In ''Episode One'', you have to escort civilians to the trains to escape City 17. This gets annoying after the first two trips, and when they start firing rockets at you.
** In ''Episode Two'', in order to get the "Little Rocket Man" achievement, you must "escort" (or rather carry, since it's just an item) a ''garden gnome'' from the first level '''all the way to nearly the end of the game'''. It's easy enough to fling it around for the start of the game, but it takes a lot of work to jam that thing in the car and keep it in place while you're dodging fire from a Hunter Chopper.
* EternalEngine: The Residue Processing chapter in the original, and the final Citadel level in the sequel.
* EverythingFades: All of the games, but taken to extremes in the original, where breaking open a large crate produces, along with a useful item like ammo or a spare HEV suit battery, a small pile of random computer equipment that begins to fade away almost instantly (possibly to make the useful item easier to spot).
* EvilTowerOfOminousness: The Citadel that looms at the center of City 17.
* EvilVersusEvil: In the first game, in some chapters (such as ''On A Rail'' and ''Questionable Ethics''), you could see HECU Marines gunning down Vortigaunts and Alien Grunts. For the most part they do a pretty good job, though they turn on you once the aliens are dead. In the second game, you can often find Combine soldiers fighting zombies and antlions. Once again, they do a pretty good job, but noticeably less so once Freeman destroys the Citadel and cut off the soldiers from their leadership.
** In OpposingForce, Black Ops would fight with Race X - and if you were quick enough, you can see Race X Shockttroopers engage Vortigaunts.
* ExpansionPack: ''Blue Shift'', ''Opposing Force'', and ''Decay'' for the first installment.
%%* ExplodingBarrels
%%* ExpositionBreak
* FaceFullOfAlienWingWong: Headcrabs, also frequently known as [[Franchise/{{Alien}} Facehuggers]]. Or as Barney calls them, "head humpers." Magnusson gives us the more scientific-sounding "cranial-conjugal parasite."
* FacelessGoons:
** All Combine have their faces hidden behind gas masks of some sort.
** In addition, the Black Ops forces of Half-Life 1 and Opposing Force wore form-fitting balaclavas.
** Most of the HECU wear chemical/biological warfare gear, including gas masks.
* FakeUltimateMook: The two tanks you encounter in ''Half-Life'' are dangerous and can instantly kill you if they are able to land a hit. However, they are immobile and if you can avoid the extremely slow-moving turret (which can't make a full 360 degree turn), you can destroy them at your leisure. The first tank doesn't even have a machine gun.
** The two Bradleys are a bit more dangerous, since their turret can actually swivel all the way around, but the first one still counts for this trope, as it oddly doesn't use its main gun, only firing missiles at you. These can be dodged and even [[GoodBadBugs redirected back at it]]. The second one, which actually uses its main gun, is much more dangerous, but it is still immobile.
* FanRemake: The much anticipated ''VideoGame/BlackMesa'' mod, which is meant to recreate ''Half-Life'' in the Source engine, and is made with Valve's blessing. The development has been a ''[[{{Vaporware}} long]]'' process, but as of September 14, 2012 it has finally been released.
* FashionableAsymmetry: Pretty much all Combine architecture and technology uses this to some degree.
* FateWorseThanDeath:
** Headcrab zombies are quintessentially this; there's a strong implication within the game that the host is still [[AndIMustScream semi-aware and screaming]] under the control of the PuppeteerParasite. This was confirmed when someone took the sound files and played them backward.
** The Stalkers -- they're what happens when the Combine capture you and don't turn you into one of their transhuman soldiers. BodyHorror only begins to cover it.
* FirstPersonShooter: Duh. What made the first game stand out to begin with was its emphasis on the "first-person" part: the entire game is viewed through Gordon's eyes.
* FinalSolution: This is what happened to the Nihilanth's race at the hands of [[BigBad the Combine]].
* FloorboardFailure: Happens quite often. Also happens in ducts as well (once into a room full of laser tripwire explosives).
* FluffyTamer: Dr. Isaac Kleiner and his pet headcrab, Lamarr. [[http://www.imdb.com/name/nm0001443/ Get it? Hedy?]]
** ''[[BlazingSaddles That's Hedley!]]''
* FlunkyBoss: A few
** The Nihilianth has an attack that will teleport you into another room. If it fails to hit you, it will instead teleport in a few Vortigaunts or Alien Controllers to aid him.
** In several of the battles with Antlion Guards, normal antlions back them up. In 2 of these battles, they continue to spawn: In episode one they keep coming until you block the holes in the ground, and in the episode 2 double guard battle they don't stop spawning until after the Guards are killed. In the latter circumstance, you have a powerful ally Vort who can easily dispatch the normal Antlions for you, allowing you to focus on the boss.
** The Gene Worm will periodically spawn Shock Troopers. Fortunately, this reveals its weak spot under its belly. Apply rocket launcher 3-4 times.
** The FinalBattle with an army of Striders at the end of Episode II has you taking out 2 dozen striders, each of which is backed up by 1-3 Hunters. Though at this point, they're more like MiniBoss creatures that [[WolfpackBoss all attack at once.]]
* {{Foreshadowing}}: In the tram ride of Half Life 1, the announcer says "More lives than your own may depend on your physical fitness."

* GameplayAndStorySegregation: Damn near none, since you're in control of your character ''the whole time''.
* GaidenGame: ''VideoGame/{{Portal}}''.
* GameMod: ''Lots''. The original [=GoldSrc=] engine and its successor Source are popular for modding in part because the SDK, which comes free with every game, is capable of effectively producing full standalone games.
* GasMaskMooks: In the first game, some HECU Marines wore gas masks. In the second game, Metrocops and Overwatch infantry all wore gas masks.
%%* GoingThroughTheMotions
* TheGoomba: Headcrabs.
* GovernmentDrugEnforcement: "Don't drink the water. They put something in it, to make you forget."
* TheGreatestStoryNeverTold: Subverted. Half-way through the original game, US Marines special forces arrive, [[WhatTheHellHero with the intent of killing everyone]] and covering up the whole event. At the end of ''Opposing Force'' we find out the military [[ItsTheOnlyWayToBeSure detonated a nuke which destroyed the facility]]. Unfortunately, this caused the portal storms, the Seven Hour War and the Combine occupation, and Gordon Freeman, [[CantStopTheSignal instead of a story never told]], was elevated to messianic status as "The One Free Man."
* GuideDangIt: For players that are used to using guns to kill enemies rather than physics, many will feel this when encountering a Hunter for the first time. They can take a ridiculous amount of damage from bullets and explosions, but have a crippling weakness to physics objects. This is made worse by the fact that the only other enemy that is really weak to physics is the regular headcrab zombie, and only to [[OneHitKO sawblades]].
* GunsDoNotWorkThatWay: A recurring theme in the Half-Life series is the SPAS-12's secondary fire somehow acting as a duel-fire, despite the weapon only having one barrel. Presumably, Valve just assumed that the SPAS-12's magazine tube is a second barrel.
* GunTwirling: The idle animation for the revolver in both games.
* HazmatSuit: "Welcome to the HEV Mark 4 protective system, for use in hazardous environment conditions."
* HeadBob: An early aversion.
* HealThyself: the insta-heal medkits and medical stations.
* HeelRaceTurn: All that's known about the Vortigants in the first is that they're invading aliens. In the second game it's revealed that they were confused and enthralled, and are now grateful for the destruction of their puppet leader. By the third, they gather en mass to support Gordon specifically.
* HeroicMime: Gordon Freeman is one of the most famous in gaming, never uttering a word of dialogue in-game.
** Barney Calhoun and Adrian Shepard from ''Blue Shift'' and ''Opposing Force'', respectively, were also silent in-game.
* HisNameIs: In the original ''Half-Life'', in the level immediately after when the Marines first appear, a nameless scientist proclaims that he must be protected and knows everything about what's going on before charging straight into Marine gunfire and being mowed down. Of course, if you manage to save him, he has nothing special to say. There's also a security guard who is midway through telling you something important before being gunned down by Assassins.
** [[spoiler:In Episode Two, Eli Vance, as it is written somewhere on this page, is about to divulge critical information on the true nature of the Combine and the G-Man, before a pair of advisors literally break into the place and suck his brains out.]]
* HiveDrone: There are several notable examples:
** The Ant Lions from ''VideoGames/HalfLife2''. The player exploits this later in the game by collecting Pheropods from a fallen Ant Lion Guard.
** The Combine operates on this concept for each dimension it conquers, by adapting the local dominant species (in Earth's case, humans) into obedient drones while draining their resources.
** Stalkers - emaciated former humans who work in the bowels of the Citadel. They are emaciated and mutilated, with crude prosthetics replacing their former limbs. And they only communicate by ''screaming''.
** Combine Synths, such as Striders, Gunships, and Hunters, may fall into this category, being support units for the Combine Overwatch.
* HoldTheLine: Several examples, usually with easily-knocked over turrets.
* HopelessBossFight: The ending of Uplink.
* HumansAreWarriors: Subtly invoked throughout the series; the HECU grunts will commonly trounce Xen forces when pitted against them in AI battles and their weapons are far more precise and deadly to the player, the Combine expend more than a little effort to turn most able-bodied humans into cyborg troops for use in their interstellar conquests, and lest we forget, one untrained human scientist in a suit of ''really good body armor'' was able to fight his way through two separate armies at once, one of them a multi-species invasion force from another dimension, the other a hardened special forces branch of the US Marines, who were tracking his every move via GPS no less. And after that, Freeman's presence and violent resistance on Combine-occupied Earth for a few ''days'' was enough to incite mass armed rebellion at their base of operations, ''level the Citadel and most of City 17,'' and guarantee the success of the plan to neutralize the Combine's capacity for off-world reinforcement. On the flip side, Earth was entirely defeated by the Combine in a mere 7 hours of open warfare, but it is worth remembering that the Combine came from another universe, which they had already conquered and subjugated in its entirety, and them versus a single planet is hardly going to be a fair fight. When all is said and done, humanity is far from helpless against the various alien war machines present in the series.
* IconicLogo: Lambda-in-a-circle. The lambda is the most commonly-used symbol for the decay constant of a radioactive element, so it's appropriate to the title, even though it isn't a perfect match (for reference, there isn't a commonly accepted symbol for half-life in physics). It also happens to look like an arm holding a crowbar...
* IdleAnimation: For each weapon and NPC - for example, Adrian pets his living rocket launcher, and Barneys pull up their pants every so often.
* ImplacableMan: Gordon Freeman himself, having mowed down countless Xen aliens, US Marines, and Combine shock troops. He even destroys Nova Prospect (one of the Combine's most heavily defended military base/prison on Earth) ''[[UpToEleven and]]'' the Citadel (the Combine's '''headquarters''' on Earth).
* ImprovisedWeapon:
** The crowbar and pipe wrench.
** Half-Life 2 has the Gravity Gun, which turns virtually anything into a weapon: Chairs, crates, tables, barrels (exploding and non-exploding varieties), benches, radiators, armoires, [=TVs=], tires, bicycles, cars, [[EleventhHourSuperpower people]]...
* InexplicablyAwesome: The G-Man.
* InformedAbility: The most technical things super-scientist Gordon Freeman has ever done are pushing a sample on a cart and plugging a teleporter in. Half-Life 2 explicitly refers to this fact. Early in the game Gordon has to plug in a cable and throw a switch, and Barney mentions that his MIT education is really paying off. It has been pointed out that the only bit of physics that Gordon ever seems to apply is F=ma. That is to say, he knows how to swing a crowbar ''really'' hard... that is until the advent of the Havoc physics engine, where Gordon now understands simple machines like levers and pulleys. According to the backstory, Gordon's [=PhD=] dissertation was a very complicated piece of work done on complex portal physics. Supposedly Gordon was given menial labor because he was young and was the new hire. Had the experiment worked Gordon almost certainly would have spent dozen of hours studying the results, running complex equations, organizing the data, and coming up with conclusions with a group of his peers. Later in Half Life 2, Eli is very eager to get Gordon out of his hazard suit and back into a lab coat. On both occasions, Gordon was forced into fight and flight due to an attack that occurred immediately afterwards.
* InsectoidAliens: The Antlions. And, arguably, the Vortigaunts.
* InsufferableGenius: Dr. Magnusson. And arguably Dr. Breen. Have you listened to his speeches?
* InsurmountableWaistHeightFence: Particularly in ''Half-Life 2'', where, to demonstrate the physics engine, you must stack things to climb said fences. In addition, the first game often had locked doors blocking your way - you had to destroy or find alternate routes which deviate into God-knows-where (such as abandoned areas of the facility or the other side of that dam).
* IvyLeagueForEveryone: Justified in the first game being set in a top secret research facility. {{Lampshaded}} by an NPC in [=HL2=]: Episode 1 who can be overheard saying "Sometimes it seems like everyone is a Doctor but me."
* JumpJetPack: The HEV Suit has a long jump module that's effectively a big rocket attached to Gordon's back for crossing gaps his normal jump had no hope of reaching. Not used very much in the game and abandoned in the sequel.
* JustifiedTutorial: There's a mandatory course when a scientist is assigned an HEV suit [[GameplayAndStorySegregation that the player can choose to play]].
* KillItWithFire: In the first game, you have to kill some Tentacles by igniting the rocket engine above it. Shortly thereafter, a Gargantua tries to kill '''you''' with fire.
** A quick and relatively easy way of dispatching enemies in Half-Life 2 and episodes, given proper equipment (namely, the Gravity Gun and exploding things like gas cans); Father Grigori makes extensive use of fire traps to thin the zombie horde in Ravenholm. Just... try not to listen too closely when you light up a zombie.
* LabPet: In ''Half-Life 2'', Dr. Kleiner has Lamarr, a pet headcrab.
* LateToTheTragedy: ''Half-Life'' was the first game to subvert this, as the first level is a leisurely stroll through the player's workplace, before all Hell breaks loose. (Ironically, with all of the [=NPCs=] telling Gordon, "You're late!") Played straight in ''Half-Life 2'', though, as Gordon is abruptly dropped into City 17 more than a decade after Earth's subjugation by the Combine, and played with - but ultimately straight - in ''Opposing Force'': Adrian is part of the first HECU responders, but his Osprey is taken out. He regains consciousness just as the military begins its pullout.
* LetsSplitUpGang: Gina and Colette need to do this now and then to solve some of their puzzles. Gordon gets this line constantly from the [=NPCs=] he's paired with throughout ''Half-Life 2'', often as a result of a bridge conveniently [[BrokenBridge breaking itself]] to split the party. Functionally, it's a gameplay tool to force the player to go it alone.
* LivingLegend: The Free Man, who starts a revolution just by showing up. The Combine are well aware of the threat he represents and unleash their everything when they find out about him.
* LivingMotionDetector: The blind tentacles in the first game, and the canceled hydra for the second, somewhat brought back via scripts.
* LockedDoor:
** You must find alternate routes due to these, whether it be a massive pipe falling through several stories, or exploding walls. Or one of many, many actual locked doors.
** Mildly subverted in ''Half-Life 2'' when you come across a door locked with a padlock and simply shoot or pry off the lock.
** Barney can do this in ''Blue Shift'' as well.
** And the barred doors which are actually Gravity Gun puzzles.
* LongBusTrip: Corporal Adrian Shephard.

* MadLibsDialogue:
** The computer voice in ''Half-Life'': Deathmatch. The HECU would speak like this when in-battle with you.
** The sound files for the Black Mesa PA system are individual words, so all PA dialogue is this.
* MadeOfIndestructium: As with most video games, almost all of the scenery is invulnerable to your weapons in the first game. Some odd exceptions include the metal grates (which can be broken with a single crowbar swing, less than it takes to break most wooden crates) and the concrete barriers which instantly shatter when you run the tram car through them.
* MascotMook: It is not uncommon to see people at standard nerd gatherings running around in cute little Headcrab hats.
* MayDecemberRomance: The implied romantic tension between Gordon and Alyx. Any relationship between them would ''technically'' be this, as Gordon is at least twenty years older than Alyx - although he's spent most of his life so far [[HumanPopsicle in stasis]], so they're physically around the same age.
* MeaningfulName:
** Father Grigori's name could have [[http://en.wikipedia.org/wiki/Rasputin two]] [[http://en.wikipedia.org/wiki/Watcher_(angel) meanings]], both appropriate. His name also means 'watchful', which describes him pretty well.
** Meek Dr. Kleiner ("small" in German) and forceful, verbose Dr. Magnusson ("magnus" meaning "great" in Latin).
** "Alyx" comes from the Greek ''alexandros'', which means "defender of men".
** Dr. Judith Mossmann calls to mind the biblical Judith, [[spoiler: whose [[FakeDefector Fake Defection]] helped to (literally) decapitate the Assyrian army.]]
** Gordon "Freeman". The resistance from ''2'' and onwards even refer to him as "The One Free Man".
* TheMenInBlack: The G-Man gives off this vibe, dressed like a bureaucrat and with his origins a mystery.
* MindScrew: The G-Man, especially in ''Half-Life 2'' and its episodes.
* MookBouncer: The Nihilanth has an attack that does this. Thankfully, he only does it four times. Unfortunately, the places he teleports you to get progressively worse. On the fourth, he simply teleports you to the third room with an [[strike:unkillable]] extremely tough boss monster.
* MookMaker: The Gonarch, a fully-grown headcrab, spawns [[GoddamnedBats annoying baby headcrabs]] which are arguably ''worse'' than the adults.
* MoreDakka: Opposing Force's M249. Thank you and good night.
** The Striders' autocannons might not look all that [[BuffySpeak dakkalicious]] alone, but when you encounter more than one... Same goes for Gunships, whice are using a similar autocannon model.
* MouthFlaps: Characters in the first game, due to engine limitations.
* {{Nerf}}: The ''Source'' version of the original Half-Life, even on hard mode, has a lot less enemies to deal with in the Xen levels (and some other rare cases outside Xen) due to there not being as many walkover game-play triggers that spawn in new enemies; especially Alien Controllers. The "Interloper" level in particular really toned down on the triggers.
* NiceJobBreakingItHero: Hey, dude, remember that big baby that you slayed in the first game? Alright, you had to kill him because he kept the hole between Xen and the Earth open, but it turns that he was also the only thing keeping the Combine at bay, and his death gave them the opportunity they needed to invade Earth.
** The Black Mesa incident.
** At the end of Half-Life 2 in the citadel in one of his breencasts, which is replayed once in Episode 1: " Tell me, Dr. Freeman, if you can. You have destroyed so much. What is it, exactly, that you have created? Can you name even one thing? I thought not".
** Two instances from when Gordon first wakes up after the resonance cascade. The first allows you to hit an elevator button...that sends an elevator with three people on it plummetting to the bottom of the shaft. A later incident has you stepping on a flimsy catwalk, causing it to collapse under the scientist on it. He even yells "GORDON!" in a WhatTheHellHero tone before falling to his death.
*** Although the elevator will fall whether you hit the button or not.
* NiceJobFixingItVillain:
** In ''Half-Life 2'', toward the end of the game, Gordon goes through a weapon confiscator. It vaporizes all his weapons except for the Gravity Gun, which the confiscator is unable to destroy. Instead, the confiscator malfunctions and ends up making it more powerful.
** In ''Half-Life: Opposing Force'', Shephard manages to deactivate the nuclear weapon that Black Ops had wired to destroy Black Mesa. Shephard is forced to watch G-Man reactivate it, and there's no way to deactivate it again.
* NobodyPoops: Gordon certainly doesn't, nor does he eat or sleep. The stasis between games might have rejuvenated him, but unless his suit has a diaper Gordon has been holding it in for at least four days. Although since the game is not really 72 hours long, there are several times in the story that he ''could'' have taken time out for those things, but which the actual game skips over because it's a game.
** In the first game, Gordon could drink. There were several vending machines, each one can dispense five cans of soda, and each soda adds one health.
* NoBikesInTheApocalypse: Inverted. There are bikes in [=HL2=], but nobody can use them.
** The inversion is subverted in ''{{Concerned}}''; Gordon Frohman rides the bikes.
* NoFairCheating:
** Sort of. You just can't get achievements in Episode Two with cheat mode on.
** Half-Life 2 Deathmatch - "This server is VAC-secured. Cheating will result in a permanent ban."
* NoOSHACompliance:
** One of the chapters in the original ''Half-Life'' forces Gordon to go through a waste processing factory. Yes, it's flesh-burning acid, but fortunately Gordon's wearing the partially acid-proof [=HEV=] suit. Similarly, Adrian Shephard in the expansion has to go through some sort of experimental blast furnace, which has no rails or catwalks to shield workers, and is only accessible via a hole on the wall.
** Then there's the ''massive toxic spill'' you can see on the opening tram ride... In fact, the whole facility is a disaster waiting to happen: there are no emergency exits directly leading to the surface in case of fire or extradimensional incursions, ceilings and catwalks collapse without warning, and an alarmingly large amount of objects, namely computers, are MadeOfExplodium.
** One of the worst is a giant fan near the silo area. The ''only'' way to turn it on is by climbing down a ladder onto a narrow catwalk beneath the blades and pressing a button. The catch is that the fan blades touch the area anyone climbing the ladder up would be, so in order to survive the task you have to press the button and then haul ass and hope the fan doesn't catch you on the way out. One episode of the "Machinima/FreemansMind" machinima openly gripes about this.
*** There is also the ladder in the elevator shaft, which is assumed to be there to fix the elevator in case it's broken. However, the only way to access said ladder [[MindScrew is if the elevator is working]].
** There's also the fact that literally everything is apparently structurally comprised, from solid concrete ceilings and walls to steel catwalks. Even most of the elevators don't work. Pretty much the only things in the entire Black Mesa facility that are able to withstand any sort of damage whatsoever are the exit doors, ''and they're all locked''. Freeman's Mind explains away the latter by stating that aliens could be teleporting into the walls. The abandoned areas (the cliff face and the old missile silo) have the excuse of no longer being maintained, but for some areas there really is no excuse. There is no reason that the two generators that run the tram to the surface should be allowed to launch giant arcs of electricity everywhere.
** In an interesting subversion, in ''Half-Life 2: Lost Coast'', the headcrab cannon has OSHA standard signs on it. Naturally, you have to do exactly what they tell you ''not'' to do.
** There's an achievement in ''Half-Life 2'' called 'No OSHA Compliance' for killing some Combine soldiers with a crane. It's the TropeNamer.
* NonstandardGameOver: In ''Opposing Force'', leaping through a portal Gordon leapt through in the main game sends you plummeting into space (instead of where Gordon landed) and accuses you of attempting to create a TimeParadox.
** Other "status report" deaths:\\
Any time you let die a scientist who is needed to open a locked door or perform an important scripted event.\\
Turning and shooting DrillSergeantNasty during ''Opposing Force's'' tutorial gets you court-martialed.

** Any overly excited person playing "Blue Shift" can accidentally (or purposefully) shoot the guard in the armory window in the crotch which the auto-aim automatically locks onto, or purposefully attack anyone else once you've receive your gun. This will result in Barney being fired for "improper handling of a Firearm." however there is a slight delay with the display and the game actually ending which gives you time to empty 1 or 2 clips of ammo into anyone you like.
* NoSenseOfPersonalSpace: Freeman's squad habitually crowd around him so closely that it can be impossible to move without bumping into one or take a shot without dinging one by accident. One imagines Gordon got to know who used which toothpaste, they're that close -- as noted [[http://www.hlcomic.com/index.php?date=2006-06-04 here]].
* NotTheFallThatKillsYou:
** Take enough damage from falling, and you WILL gib.
** More true to the trope, grabbing a ladder within inches of the terminal surface prevents any damage.
** Fall any distance into water, no matter how shallow, and you'll be fine. Assuming it's not filled with leeches.
* NotWorthKilling: The apparent reason why Barney Calhoun, Gina, and Colette successfully managed to escape Black Mesa on their own two feet, while Freeman and Shephard both ended up captured and put on deep freeze by the G-Man.
* OhCrap: Toss a grenade into the sniper's nest, and one of his possible responses is a vocoder-muffled but still discernible "...SHIT!"
* OneBulletClips: Handwaved - this is one of the [[AllThereInTheManual features of the HEV system's offensive capabilities.]]
* OneManArmy: Oh, boy.
%%* OntologicalMystery
* OurZombiesAreDifferent: And terrifying.
* OutrunTheFireball: A grunt throws in a satchel charge in a tunnel you're crawling through in the first game. Better run [[labelnote:*]]In either direction, since the hatch is only a few feet away and [[GoodBadBugs the explosion doesn't damage you if you're right where the satchel charge is]][[/labelnote]].
** Practically your objective throughout Episode One. [[spoiler:You pretty much succeed, but not entirely.]]
* PathOfGreatestResistance: In Freeman's Mind he often says that when he gets lost, the best bet seems to be to follow the trail of corpses and bloodstains, and that the more dangerous the situation, the more he seems to be on the right track.
* PersonalSpaceInvader:
** Headcrabs.
** Snarks in the first game, even worse than the headcrabs.
** Half-Life 2 brings Fast Zombies, Antlions and Rollermines, which love to cuddle up real close to you while they attack.
* PhotoprotoneutronTorpedo: Tau cannons and gluon guns.
* PlotPoweredStamina: Gordon never has to stop to eat, sleep, or take a piss (though one might forgive that as a function of the suit). While he did get a break in between the original game and ''Half-Life 2'', in which the G-Man probably started him at optimal health, he's on the go from then on with only brief moments of unconsciousness at the start of each installment. It isn't as if time isn't passing either; the sun starts setting as Gordon arrives at Black Mesa East, Ravenholm takes place at night, and the sun is just rising as Gordon emerges from the mines. When he arrives at the Vortigaunt Camp at the end of "Sandtraps", the sun is setting again, and at the end of "Nova Prospekt", despite a week passing in relative terms, Gordon still hasn't had any rest. The finale appears to take place shortly before sunset, so even if all you count is the original ''Half-Life 2'', Gordon is up and moving constantly for over forty-eight hours without a break.
* PointyHairedBoss: Dr. Wallace Breen was the administrator of Black Mesa at the start of the first game. Given, oh, ''everything that's happened since'', I think it's safe to assume he wasn't the most competent administrator ever. Of course, in the sequel, [[TheQuisling he]] gets [[MisanthropeSupreme worse]].
%%* PortalPool
* PowerArmour: The HEV suit. The military PCV only half-qualifies, since it's just an armor vest built with the HEV electro-reactive armor.
** Specifically averted with Barney Calhoun in Blue shift. Your armour is probably about as strong as the power armour, and despite coming across some HEV suit chargers here and there, you can't use them and can only renew your armour by picking up "undamaged" armour from other, less fortunate guards.
* PowerLimiter: The collars and bracers the enslaved Vortigaunts wear in the first game diminish their powers and render them the {{mook}}s of the Xen invasion. In the second game, when they can use their full powers... well, see CrowningMomentOfAwesome.
** Note that the Combine employ similar shackles for the Vortigaunts they capture.
* PutOnABus: Corporal Adrian Shephard.
** Barney Calhoun appears to have been put on a train at the end of ''Episode One'', not to be seen since. He is missed.
** Colette Green and Gina Cross haven't been seen since the end of ''Decay'', along with Dr. Keller.
** Not really a major character, Otis Laurey from the Gearbox expansions ''Opposing Force'' and ''Blue Shift'' became an AscendedExtra in ''Decay'' ([[AllThereInTheManual in the manual, at least]]), but hasn't been mentioned at all in the main ''Half-Life'' {{Canon}} since.
* PunchClockVillain: The HECU Marines are just as confused as to why they're killing the Black Mesa workers as the workers themselves. Well, ''some'' of them are,at least.
* [[ConvectionSchmonvection Radiation Schmadiation]]:
** Only direct contact with radioactive waste causes any issues. Fair enough for Gordon, who has the HEV suit (designed for that sort of thing), not valid for the few times [=NPCs=] also get near it unless it's stabilized.
** Also played straight by Gordon himself in Episode 1, when he enters a reactor compartment flooded with radiation. Yes, he has his HEV suit, but since he ''never puts on the helmet'' his head is still completely exposed.
* RealityBreakingParadox: Following Freeman into the Xen portal in ''Opposing Force'' gives a NonStandardGameOver due to the TimeParadox.
* RecklessGunUsage: The player can ''twirl'' a loaded revolver at vital characters (it's part of an idle animation, and all conversations are in-game so you'll see it a lot) which almost guarantees a friendly fire incident or six. The sequel makes Gordon lower his weapon automatically when pointing the crosshairs at a friendly NPC so it no longer applies, though the player can still fire it (harmlessly) without aiming anyway.
* RedemptionPromotion: In the first game, when they're your enemies, the Vortigaunts are fairly low-level, easily disposed Mooks. In the second game, when they're your allies, they're incredibly powerful fighters whose beam attacks can kill an enemy in one hit and send them flying a few dozen feet. They're even powerful enough to [[DidYouJustPunchOutCthulhu counter-act the power of the then-seemingly unstoppable G-Man]]. He is not amused by this.
** Possibly justified. See those shiny green things they wear in the first game? Those are slave collars similar to the ones the Combine put on them. They can't use their full power until the collars are removed.
* ReferenceOverdosed: The series is notorious for having numerous hidden chemistry/physics nods. A handful of them are:
** The original game is named Half-Life, and a major objective involves Freeman working with the Lambda Complex.[[labelnote:''Exp.'']]The lower-case lambda is used to represent [[http://en.wikipedia.org/wiki/Exponential_decay exponential decay]]; in other words, the ''half-life'' of radioactive materials.[[/labelnote]]
** The original game's expansions are named [[http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion#Newton.27s_3rd_Law Opposing Force]], [[http://en.wikipedia.org/wiki/Blueshift Blue Shift]], and [[http://en.wikipedia.org/wiki/Radioactive_decay Decay]].
** Additionally, chapter names often allude to this through double meanings, such as [[http://en.wikipedia.org/wiki/Surface_tension "Surface Tension"]].
* ReflectingLaser: The Tau Cannon / "Gauss". Technically a "hypervelocity projectile" weapon, but works like an insta-hit laser that reflects off any solid map surface at 45 degrees angle or less to the horizontal.
* RememberTheNewGuy: Barney Calhoun, who was technically around and named before ''Half-Life 2'', but never interacted with Gordon (although many characters who looked and sounded exactly like him did). A more blatant example of this is Dr. Magnusson in ''Episode Two'', who ''definitely'' wasn't around before then, at all, and the scientists Barney helps get out in Blue Shift.
** Amusingly, the BrickJoke about [[spoiler:the microwave casserole]] only works because he didn't appear in the original ''Half-Life'' (at least, not with the same voice or model -- see YouALLLookFamiliar below).
* ResearchInc: Black Mesa was a private contractor.
* RetCon: Too many to list here. A complete list can be found on the [[http://half-life.wikia.com/wiki/OverWiki:Retcons Half-Life wiki]] though.
* RevolversAreJustBetter: The revolver is much more powerful than the semi-automatic pistol in both Half-Life 1 and 2, and perfectly accurate.
* RocketJump: Can be done with various explosives.
** A safer version of this is used in Episode Two to reach the rocket cache, using a grenade and a metal 'catapult' on hinges. The achievement is aptly named 'Gordon Propelled Rocket', which is also an inversion of 'RPG'.

* SchmuckBait: Early on, after the resonance cascade, you reach an elevator with a large warning sign next to it - "In Case Of Fire Do Not Use Elevators" - should you press the button, an elevator full of scientists will fall screaming to their doom (though if you don't press the button, the elevator will fall anyway once you break the door's glass to continue). (The developer who thought this up said that it worked both as a game element and as a message to other developers - "Enough with the [[FetchQuest d*mn button puzzles]] already.")
* ScreensAreCameras: Most screens seem capable of this, particularly the Combine screens.
* ScriptBreaking: A staple of speedruns.
* ScriptedEvent: There are no {{cutscenes}}, so the ''Half-Life'' series uses these almost exclusively for storytelling.
* SecondHourSuperpower: The HEV suits from both games.
* SequenceBreaking: The physics engine and stackable boxes allow clever players to bypass some of the challenges. There are three areas in "Nova Prospekt" where the player must use mounted turrets to repel the Combine. In two of those areas, it is possible to stack boxes to block some of the attack routes and, in the second, to escape to a more defensible position. Alternatively, a dedicated player may choose to bring along the turrets from each area to the next, giving you far more firepower than you'd normally have.
* ShoutOut: In ''Opposing Force'', two are mentioned from ''StarWars''.
** A security guard asks a scientist if he has seen the new IG-88.
** [[http://www.youtube.com/watch?v=uHU8tU2DbGI&feature=related And at the end of this segment, you see doors that look like they were from the trash compactor room]] in ''ANewHope''.
** Not really a positive shoutout, but during the antlion defence portion early in Episode 2, Griggs mentions that he [[UsefulNotes/GeorgeWBush "misunderestimated"]] the size of the Antlion force.
** In ''Opposing Force'', drill instructor T. Barnes asks a recruit where he is from, and gets the answer "Texas".
--->'''T. Barnes:''' Holy cow! [[Film/FullMetalJacket You know what comes from Texas, don't you]]?!
** In Opposing Force, during the pit worm chapter, there is a panel with buttons on it. The buttons are labeled "Valve" and "Gearbox."
** Dr. Breen is likely a ShoutOut to Colonel Breen in ''Series/QuatermassAndThePit'', an ObstructiveBureaucrat who's frequently observed to go against the ScienceHero.
** In ''Episode Two'', You can find Series/{{Lost}} references - a Dharma Initiative Style Logo and a computer with the numbers on it.
** The elevator in Unforeseen Consequences in the [[VideoGame/HalfLife1 first game]] is modeled almost exactly off of the one in ''{{Manga/Akira}}''. The two expansions that feature this same elevator even acknowledge this (at least, Gear Box does) in that the brush is named "akiraelev".
** One of the deathmatch maps, [=Halls2=], is based of of a similarly constructed netplay level in the first ''{{VideoGame/Marathon}}'', Halls of Death. [=Halls3=] for ''VideoGame/HalfLife2: Deathmatch'' shows the same resemblence.
* SickeningCrunch: When you take fall damage.
* SlaveMooks: The Stalkers and all Synths are this.
** Vortigaunts used to be this for the Nihilanth. Now that they're [[HeelRaceTurn freed and]] [[RedemptionPromotion joined the good guys]]... see {{Crowning Moment of Awesome}}.
* SnipingMission:
** You must dodge Black Ops snipers and trip wire mines in ''Opposing Force''... and snipe them back.
** You also have to save Barney from Combine Snipers later in the game. This was supposed to happen multiple times in the beta.
** While never performed by the player, Alyx takes this role twice, one time during each Episode, to your benefit.
* SoftWater: Which saves you from massive damage ''a lot''. The engine demonstrates this trope ''aggressively'': custom maps use ankle-deep water to break several story falls all the time. Just don't jump into any water infested with parasites or that has broken electronics nearby, or it's instant death!
%%* SortingAlgorithmOfEvil
%%* SortingAlgorithmOfWeaponEffectiveness
* SpaceMarine: Averted with the [=HECU=], which don't even have any specialized equipment, save for the PCV powered vest ''some'' soldiers are assigned.
* SprintMeter: The auxiliary power source. It also powers the [[TenSecondFlashlight flashlight]] in ''Half-life 2'' and ''Episode One'', so don't run too much when you need it.
* {{Sssssnaketalk}}: G-Man in the first game. Changed to him putting syllable emphasis and sentence pauses in the wrong places in ''Half-Life 2''.
* SteamVentObstacle: They appear in both games. You have to time your passage through some, but others are static and you have to find a valve to shut them off with.
* SuperheroSobriquets: The One Free Man.
* SuperSoldier: Gordon's a god with the HEV suit. Shephard more accurately fits the bill, being an actual soldier.
* SurprisinglyHappyEnding: [[spoiler: At the end of Blue Shift, you manage to escape.]]
* SuspiciousVideoGameGenerosity: Whenever this series drops you into a room stocked with ammo, armor and health packs you have reason to worry. Perhaps justified. With G-Man's ability to teleport any where and his chess master behavior, he could very well be the one leaving some of this caches at strategic areas for the protagonists to find.
* SwissArmyWeapon: Gordon Freeman's suit. Not only does it protect from dangerous hazards, it can block bullets, generate air, it has a flashlight, it can [[HyperSpaceArsenal hold many weapons]], allows Gordon to run faster, and has a scope.
%%* TakeYourTime
* TechnicallyLivingZombie: The headcrab zombies... probably.
* TimeStandsStill: The G-Man pulls this on you a few times.
* ToiletHumor: not really in the game, but [[http://www.youtube.com/watch?v=K0SI7MYwPv4 this]] fan-video will [[CrowningMomentOfFunny make you hurt]].
* TooDumbToLive: Gordon sometimes does some incredibly stupid things, like deliberately entering a ''metal coffin'' right into Breen's hands. Twice. Breen even lampshades this.
** A fair number of Black Mesa staff also succeed in getting themselves killed under blatantly stupid circumstances, such as running directly into obvious traps, while HECU and Black Ops soldiers can sometimes blow themselves up with their own grenades. While some of it is scripted, many instances can also be attributed to ArtificialStupidity.
* TorturedMonster: The zombies are humans who have been turned into PeoplePuppets and mutated by the parasitoid headcrabs attached to their heads. In the second game they can be heard screaming for help as they attack you.
* UnbrokenFirstPersonPerspective: The first game was the TropeCodifier for using the trope for narrative effect - the game never breaks from Freeman's perspective for the duration of the game, and there are no cutscenes. This carried over into the sequel and the various expansion packs and episodes.
* TheUnintelligible:
** Originally, Vortigaunts, who would gibber and only knew one English phrase: '''''DIE!!'''''
** Headcrab zombies from the second game count, until you play their speech files [[http://www.youtube.com/watch?v=dxbd-Cg50Nk backwards]]. Then you wish they were unintelligible. In the first game, they'd simple gurgle at you.
* UnreliableCanon: Creator/ValveSoftware once stated that 'canon is uncanonical' to reserve creative freedom for the games.
* UnusableEnemyEquipment: Averted. Even if it's alive. Even if it tries to bite your face off. Also played straight with the Combine Sniper Rifle. Also, even though they are allies, not enemies, Alyx's Machine Pistol and Father Grigori's Winchester Rifle are unique to them.
* UnwittingPawn: Gordon Freeman, and how! Adrian Shephard is a close second.
* UseItem: The same key is used to open doors, push buttons, talk to people, pick up things...
* TheVeryDefinitelyFinalDungeon:
** You travel to an alien factory. Of ''course'' the BigBad's near.
** In the sequel, once you enter the Citadel, you ''know'' there's going to be a boss at the top.
* VideoGamesAndFate: The strict linearity and use of No Sidepaths, No Exploration, No Freedom in the series is a plot element as well as a gameplay device, reflecting how Freeman's actions are being controlled by the G-Man (who at one point boasts that he'd rather not offer Freeman "the illusion of free will").
%%* VideogameSetpiece
* ViolationOfCommonSense:
** A live wire dangling from the ceiling just zapped some headcrabs who were very close to a vent, after zapping the faceplate off that same vent. Where are you supposed to go in order to avoid going under the wire? Into said vent, of course!
** There's a huge wall of double-stacked concrete barriers in your tram car's way. How do you proceed? By ramming the tram car right into it!
** Climb into a hanging metal coffin that completely restricts your movements to make it into the enemy base? Sure. Do it again, even though the last one resulted in your weapons being confiscated and only dumb luck keeping you alive? Of course.
** Locked in a room with a pit that has giant whirling fan blades the size of a bus and a ceiling that's boarded over. What to do? Jump out over the fan blades [[strike:and turn into chunky salsa]] to get blown upwards, naturally!
* TheWallsAreClosingIn:
** In the original game, a pair of {{mooks}} capture the player character and, rather than [[WhyDontYaJustShootHim just shooting him]], toss him in a trash compactor. Which he then escapes via conveniently stacked up garbage.
** The ExpansionPack ''Opposing Force'' has a trash compactor that looks even ''more'' like the ''StarWars'' one.
* TheWatcher: The G-Man. It is also suggested that there are several other parties/individuals keeping track of the Combine's activities and are all trying to affect the outcome of the struggles on Earth:
-->'''Breen''': ''How about it, Dr. Freeman? [[spoiler:Did you realize your contract was open to the highest bidder?]]
* WeHaveBeenResearchingPhlebotinumForYears:
** It's revealed in Opposing Force that [[spoiler: the scientists have been experimenting with Xen life for long enough to have a terrarium and have modified a Barnacle to use as a weapon.]]
** The main game already had plenty of hints of this. In "Questionable Ethics" you find several Xen creatures contained in laboratories. While on Xen yourself, you come across dozens of corpses wearing [=HEV=] suits. WordOfGod has also said that the sample Gordon pushes into the anti-mass spectrometer in the beginning of the game is the same kind of crystal that protects Nihilanth.
* WeaponOfChoice: Gordon is always depicted carrying the red crowbar.
* WhatHappenedToTheMouse:
** Remember Adrian Shephard? The protagonist in Half-Life: Opposing Force? What happened to that guy? If we believe Gabe Newell, Valve is itching to get him into the main storyline.
** In VideoGame/{{Portal}}, there's an EasterEgg in which all keyboards have the letters A,S,H,P, and D colored yellow, referencing the [[FunWithAcronyms Aperture Science Handheld Portal Device]]. When someone inside Valve realized that it looked like 'Adrian Shephard', they decided [[ThrowItIn it'd be funny to have every letter that makes up 'Adrian Shephard' be yellow.]]
** Race X (the alien race from the Opposing Force expansion) is occasionally wondered about, but according to [[WordofGod Marc Laidlaw]], they don't matter to the HL Universe. Gearbox invented them to primarily experiment for future games of their own, and the minute Gearbox stopped making HL games, [[DroppedABridgeOnHim they vanished]].
** And none of the characters from ''Decay'' (in paticular the two main characters, Gina and Colette) have been seen since that game's ending.
* WhatMeasureIsAMook; Both {{Mook}} and OneManArmy are {{Deconstruct|ion}}ed via this; sneaky players can listen in on the {{Arm|iesAreEvil}}y as they have weird self-hating conversations about [[CavalryBetrayal slaughtering hundreds of scientists who expected them to RESCUE them]] - and later their rage at the player, who they believe was the mastermind behind the invasion and have been slaughtering their comrades wholesale. On the other hand, one of the Marines laments having none of the scientists fight back.
** There's also the ''Opposing Force'' expansion pack for the original game, where you play as a HECU marine. While said Marine is comatose for most of the original game and wakes up just as the military begins pulling out, your allies are all trying to work together to pull out.
* WithinParameters: A scientist monitoring the experiment at the start of the game [[TemptingFate dismisses power-level fluctuations (presaging the Resonance Cascade) as this]].
** Used again in Episode 2 by Kleiner when observing a eight-and-a-half pound weight difference in the rocket they're planning to launch. [[spoiler: It's Kleiner's pet headcrab, Lamarr. And a garden gnome, if you did the achievement.]]
* YouALLLookFamiliar:
** HECU grunts aren't that diverse. Neither are the citizens of City 17.
** Headcrabs only seem to latch on to people wearing white shirts and blue jeans. Though this could be because most of the humans you see are forced to wear identical blue uniforms like in prison.
*** Continuing the tradition, they only latch to standard Overwatch Soldiers once they're out of Combine control. Metrocops and Combine Elites are perfectly safe. May be justified as higher ranked Combine achieve that rank by submitting to further cybernetic augmentation; there may not be enough human left for the Headcrabs to consider them proper hosts.
* ZombieApocalypse: [[{{Reconstruction}} Reconstructed]]. In ''Half-Life'', zombies are created by alien crabs latching onto peoples' heads and taking control of the person's nervous system. The person effectively dies in the process, but remains animate because all the vitals that are necessary to live are in the crab, not the corpse. They're also still self-aware, just not in control.
** Practically, this is what happened to nearly every single place after the Black Mesa Incident allowed headcrabs onto Earth and Combine started to use headcrab shells. There is no area in Half-Life 2 and its episodes where there would be no headcrab zombies or headcrabs wandering in search for a victim. The most direct example of this trope is Ravenholm, a town which was housing the refugees from City 17 before it was subjected to massive bombardment of headcrab shells and turned into Hell on Earth [[BadassPreacher with a single survivor doing the work of saving the lost souls]] by the time Gordon shows up.