2½D: As mentioned below, one of your weapons can fire into the fore- or background, as well as enemies sometimes appearing from said locations. The game makes this clear in no uncertain terms in the opening mook force, which appears in the foreground, before spinning around and entering your 2d plane. Interestingly, the camera also spins back and forth in various angles relative to your craft, even as you stay in the same plane (so that you are looking from a rear 3/4ths view at one moment, and then from below and to the side in another moment. Several boss battles even have the camera pan before the boss uses some attack or another, not to mention many points in the levels themselves.
You even get a short first person view point just before the first boss, but only if you didn't get Secret Bonus 3.
Action Bomb: One of the enemies in stage 5. They don't attack on their own, but if given enough time, will self-destruct. Green-lined ones will explode into a plasma Sphere of Destruction, while the more dangerous red ones will explode into a starburst of projectiles.
After the End: The events of the game take place years after the great war; there's nothing on Earth but wasteland outside the Cyber Punk city.
Gloriously showcased by taking the alternate route at Level 1. You descend through what seems to be a giant cavern underneath Gesetz' Megapolis. The scenery shifts from the bright, Blade Runner-esque city to a dark landscape littered by broken skyscrapers, presumably berserk automatons, and at one point, a presumably unexploded inter-planetary ballistic missile.
All There in the Manual: The only real indication to explain why the Earth forces speak German (otherwise, one could easily assume they only speak German in that part of the world), and where the capital city is located is because the instruction manual barely mentions that the city was built over the ruins of an autobahn.
It also mentions briefly that Germany (or what's left of it) set up a One World Order after the bombs fell, while the defeated eventually became Selene.
Animal Mecha: The monkey mecha Ausf A Gestell, who is ironically not named after an animal.
Armor-Piercing Attack: The Riot weapon can pierce enemies' facial armour and hurt them directly, something which even the Flash cannot do (on certain enemies and bosses). Justified as it's an electrical weapon and fries them from the inside out.
Attack Its Weak Point: Most of the minibosses and bosses can be defeated quickly if you know where to shoot them in. The same applies to larger enemies that can be defeated by shooting them in their engines and such.
Hint: Shoot the part that has a green glowing thing (such as a visor) on it. Nine times out of ten it's the weak point.
The Mosquito gun pod, a manual-guided missile, sounds cool until you find out that the missile is guided by the fighter's movement.
The Python, although one of the most damaging weapons in the game, is shot out in a string of shots somewhat randomly controlled in opposition to the player's motion. As such, it is quite difficult to damage the enemy with it.
The Flash, which shoots a cool-looking purple beam that slices through everything (bypassing armor and still going after that) but the ammo is ridiculously rare AND limited in amount. Unless you unlock the secret ship that always comes with 9999 ammo with any gunpod.
Ax-Crazy: The apeMini-Boss of Stage 5, Ausf. A Gestell, attacks your char like a deranged monkey: it frequently tries to swat the player's ship, and if knocked down, throws a crate at the player (similar to a certain ape).
Befittingly enough, the background music when you fight it is called "Madness".
Bilingual Bonus: All the enemies from stages 1-6 speak in German. If you know the language, you can understand that they're trying to kill you. Most of the dialogue, however, is incomprehensible due to sound effects and alarms that go off when they talk.
The Cannon gunpod. Pretty solid firing rate, ammo is plentiful, and its damage is reliable. As long as the bullet has disappeared from the screen, you can fire another round. This can lead to some terrifyingly high rates of continuous fire if you get up and close to the enemy. Even better, the Cannon pierces through lesser enemies, and a particular section in Stage 2 has mooks lining up, as if begging to be shot by the Cannon.
The Spreader can fall into this. Like the grenade, it is one of the two weapons that can shoot backwards; they are the only two weapons that can effectively fight the Stage 3 Boss, Gustaff, who is prone to try shooting you from behind. Also, like the Cannon example above, getting real close to the enemy can result in some terrifying rates of fire. Even better, nearly the entirety of Stage 4 includes massive amounts of mooks and later, tight corridors, a role that a spread-shot weapon is really suited for.
The Grenade gunpod. It does the most damage-per-shot out of all the weapons in the game, but it has an arcing projectile and hence, slightly more difficult to land accurate shots with. Then again, due to its low ammo, it's better used on bosses and mini-bosses anyway, and so accuracy is much less important. One more thing, though; it can fire backwards too, which is real handy to fight Gustaff with (see above).
Your humble Vulcan. Widely available and can reliably destroy your standard mooks. Combined with the Endymion Mk. III's double standard guns, it can do some serious damage over time.
Boss Warning Siren: The game gives a warning that is themed into the level. For example, in the first level, after fighting your way through the city, the police decide that they can't take you down, so they follow behind you like a low speed chase, keeping their sirens going while they basically escort you right towards the first boss. Following bosses might have klaxons sounding off to indicate that the boss is powering up and becoming mechanically operational, or have someone over a PA system order for another boss to scramble and prepare for battle.
Breakable Weapons: While attached to your ship, the gun pods can gradually collect damage from collisions and enemy fire and eventually be destroyed if replacements are not collected. The ship's bare manipulator arm, on the other hand, is completely indestructible.
Cavalry Betrayal: Your relief force of EOS fighters become this at the end. On the other hand...
The Cavalry Arrives Late: The Bad End implies that the EOS fighters really did come to assist you and were actually late.
Chicken Walker: The Star (Starling) and Panzerstar (Armored Starling) enemies, as well as the boss Sturmvogel (Thunderbird). Fridge Brilliance when you consider that they are named after birds in German.
Climax Boss: Schwarzgeist, or Black Ghost, the stage 6 boss.
Collision Damage: Double-subverted. Your ship does not get destroyed when you contact a hard surface, but will if you continue pushing into it.
Dark Reprise: The track "Conflict" is a dark reprise of "Dawn". Dawn is a fast-tempo, somewhat hectic techno piece that picks up quickly as you assault the enemy's launch base while mooks swarm you. Conflict instead starts in a calm, almost ambient trance, before Dawn's leitmotif plays. Slowly, the tempo picks up to be the same, and later, even faster than Dawn. Notably, the stretch where Conflict plays has the game's most crowded screen-filling throngs of enemies.
The Dev Team Thinks of Everything: Half the replay value is finding out all the secrets the game offers, but mostly, it's finding what attack patterns the bosses don't have. There are repertoires for just about any conceivable scenarios, including loss of specific weapons and armor, as well as movement/location. For example, see Gecko, the Spider Tank in the picture above? If you try to outsmart it by taking refuge directly above it, it will fire airburst depth charges to ward you off. Even better, nearly each boss can be "time-outed", and some bosses have a unique Villain Exit Stage Left animation. For example, the Stage 5 Humongous Mecha boss Ausf. D Dürer will go to the background and fire a flashbang grenade, before literally jumping off the boss fight stage.
There is a Bonus Boss that can only be fought if you destroy a specific part of the penultimate boss. The game has a special soundtrack just for that case.
The Hedgehog gunpod. It's a bomb/airburst depth charge launcher that only shoots up or down. There are those select times where you are either pinned to one side of the screen or can abuse a Boss's weak point, which are often directly on top of it. This gunpod is made just for that occasion. Also, it has plenty of ammo and can rapid fire its depth charges, making for a curtain of long-lasting wide explosions for your enemies to run into.
The same goes for the Blade, which is essentially a lightsaber for your ship - obviously, it has VERY limited range, but a very skilled player can turn it into Hell for standard enemies and boss parts. Try performing the Shoryuken motion (forward, down, forward) motion and the Blade will extend itself to the whole length of the screen, and waving it around by pressing the arm position change button on the Endymion models will make it slice and dice enemies.
Strangely enough, the most powerful weapons at your disposal appear to be your ship's engines (fired behind you when you change the speed of the fighter) and the manipulator arm you use to pick up weapons.
Direct Continuous Levels: For levels 1-6. Your craft is shown heading to its next destination while Hyperion directs you to your next objective.
Gatling Good: Your ship's basic machine gun, the Vulcan, and the Juno all fit into this. Especially the latter two.
Getting Crap Past the Radar: The song "Shudder" has a few f-bombs dropped in it. In an E-rated game, of all things. Due to the vocal sample's extreme rapid fire delivery, as well as the fact that most players will be more preoccupied with the bullet-filled screen most of the time, it's very understandable.
The Astraea fighter allows the player to wield two gunpods simultaneously.
Gratuitous English: The folks of Selene speak a slightly mangled kind of English, even if they are correctly pronounced.
"Received telegram from conduct satellite Hyperion. Order the following operation. The armored train is spotted leaving the city on their way to the east. Pursue them, and locate the enemy supply route."
Shown Their Work: The player is operating in the heart of enemy territory and military communication often sounds terse compared to common speaking. The point is to relay precise information as quickly and in few words as possible to avoid enemy detection or jamming. Due to the repeated use of the words "telegram" and "satellite", the info is being sent in short bursts for the same reason... just like Real Life military teletype communications.
Gratuitous German: Meanwhile, German becomes Earth's global language. Starting with the federation being called "Gesetz" (German for "Law")...
"Achtung! Einhänder kommt! Drei sekunden bis kontakt!"
The Greatest Story Never Told: The epilogue mentions that both the Earth Force and Selene have deleted every record of the protagonist's existence and endeavours. Only "those who actually fought and were wounded in the war know the name of 'EINHÄNDER'."
Headshots Kill Robots: Played straight almost all the time — opponents have a glowing green spot that happens to be the weak-armoured cockpit, and that spot is usually the head. Destroying it will destroy the Mook/Miniboss/Boss.
But not always; in the case of Gecko, the weak spot is the bottom, and for Schwarzgeist, it's the middle section. The Sturmvogel's weakpoint, meanwhile, is not the "head" of the Boss, it's the armor that combines with it.
Heavily Armored Mook: The enemy in stage 2 called "Star" (Starling in German) returns as a tougher-to-beat armored version in stage 5 called "Panzerstar" (Armoured Starling).
Taken Up to Eleven with the Sturmvogel, which is also named after a bird ("thunderbird", literally). The boss not only looks like a large, scaled up Star unit with additional armaments, it actually has a Mecha Expansion Pack armor which is the real target.
Helpful Mook: The Accidentally Assisting type, they are your source of ammo.
High-Altitude Battle: Stage 6 has your ship fly near outer space in order to destroy a large, presumably combat-capable space shuttle before it can deliver its payload. After you do destroy its boosters, it performs a last-ditch effort and launches the satellite anyway. Cue the Boss Battle.
Homing Projectile: The Wasp weapon, which can home in on enemies in the background AND foreground!!!
The side weapon of the Schabe when it collects a wasp will also home in on enemies, background targets and foreground targets alike.
I Am Not Left-Handed: Destroy both of Greif's weapons and he'll whip out a laser cannon to replace them.
Infinity+1 Sword: Astraea Mk.II, one of the secret fighters; it functions like the default Astraea Mk.I, but starts with 9999 ammo for both gun pods. Now arm it with the rare gun pods, Juno and Flash...
It's Up to You: Subverted. While the intro animation only shows a single fighter, Selene actually sent a team of fighters. You can assume that they're off doing their own thing while you do yours.
Kaizo Trap: The submarine that appears before the Mini-Boss in Stage 4. If you "defeat" it the conventional way by destroying the body, its cockpit will detatch from its body, and fire out a very deadly spray of rapid shots.
There's also the Miniboss of Stage 4 itself. When defeated, it will flail its arms about like a drowning guy... and these can still collide with and kill you.
Successfully defeating the penultimate boss will award you with the mission clear screen. Destroy it a certain way, however, and you get treated with a full blown midboss. While it is weak, it is fast and throws you quite the bullet curtain. Naturally, losing to it means you have to destroy the whole boss again.
Kill Sat: Two of 'em. On crack. The "final" level is about stopping the first from reaching Selene. The second is your heretofore unseen commanding satellite, which resembles a Humongous Mecha more than anything else.
LethalJoke Character: Schabe, the other secret fighter, has nothing but a machine gun, but picking up gun pods will upgrade it. While the Schabe might seem weaker compared to the basic Einhanders (e.g. it does not have any defenses whatsoever), it gains a different secondary fire as different gunpods are collected to level it up. If the Schabe happens to pick up a Wasp or Mosquito gunpod... hoo boy, it gains INFINITE HOMING SHOTSOF DOOM!
Your ship, called an Einhander (one-handed sword), has a single arm-like extension that can equip different gunpods.
The shape of the ship itself vaguely suggests a hand, with the turbines, wings, and the manipulator arm being the fingers. Both the cover of the game and the intro narration refferences this.
Mini-Boss: Each level has at least one (Greif, Garnele, Gecko, Salamander, Ausf A Gestell) while Stage 4 has another in the large submarine.
Mook Maker: The military train cars in the second stage spawn lots of small shooting drones and attack vehicles. Its locomotive part, Spinne, has a dedicated arm to launch small fighter jets at you.
Your welcoming committee to Stage 4's underground Naval Warfare Research and Supply Facility are waves upon waves of fighter aircraft. Later, you come across a submersible carrier that is responsible for launching said fighters.
The Strategem Spacecraft has the ability to spawn flying mooks which you can kill enough of for a Special Bonus.
Multi-Armed and Dangerous: Spinne, the train car with four weapons attached to its arms. There's a good reason why it's named "Spider" in German.
Ninja Pirate Zombie Robot: Salamander can best be described as a "Stingray submarine with arms that hangs onto monkey bars", a tail that can heat itself into a swinging blade, and it has a kickass Wave Motion Gun-esque water cannon that can make even Metal Gear RAY green with envy.
Nonstandard Game Over: Allowing the timer to expire at the start of stage 6 causes your ship to shut down and plummet to Earth, where it is immediately set upon by German forces. The game ends here even if you have extra lives remaining.
Your gunpods can absorb a limited amount of damage for you before they are destroyed. If you are skilled and/or lucky enough, you can even use the bare manipulator arm to block attacks, and the arm itself is indestructible. This is reflected by the color of the equipped gunpod's background. Green means it has a healthy amount of HP. Yellow means it is damaged. Red means it is about to break, and the weapon itself should blink red. Acquiring the same gunpod will restore its life immediately.
The Schwarzgeist fires a large burst of missiles at you. If your arm is empty, you can go into the top left corner, hold up and left, and block all 20-odd missiles which will hit the arm and explode but not do any actual damage do you.
One-Man Army - By the end of the game, you've single-handedly ended the war by shooting down anything that can fight. On BOTH sides. And lived.
Outrun the Fireball / Out of the Inferno: If you get a secret bonus on the right stage, you end up going up a tunnel with the explosion just behind you. Then right before the boss, the entire thing goes up and you begin the boss fight exiting a giant pillar of fire. Badass.
There's also a rewarding detail: If you fight the regular boss, the paint job is shiny smooth. If you unlock the secret, the boss's body will be burnt and (cosmetically) damaged.
Palette Swap: The first boss, Drache, has two versions. The one you go up against depends on whether you unlock the secret bonus while fighting the Greif — he's normally green, but is blue if you got the secret bonus. By the way, the blue version can randomly spawn a Juno, a very powerful big brother variant of the Vulcan.
Power Equals Rarity: The Flash, Juno, Python, and Mosquito can only be obtained very few times per playthrough, although the latter two are Awesome, but Impractical due to their weird trajectory and control scheme respectively.
You also get Tech Points added to your score by destroying the environment, such as the neon signs in the first level, or causing a nuclear meltdown by shooting some support struts located above a reactor and letting gravity do the rest.
Certain special weapons can be acquired by destroying certain parts of the enemy. Part of the fun in playing the game is seeing just how far you can strip the bosses naked. The Ausf A Gestell has about 20-some separate weapon and armor points you can remove before you destroy it or run out of time and move on. It just looks like a bare-bones frame when you're done. You can acquire the Flash gunpod if you allow it to kick enough boxes at you in the process.
Destroying all the signs near the end of the first level will allow you to net an early Riot pickup, which is useful for beating Greif in just the right way to get the alternate path.
Stage One Nuke: Three of them in fact. Destroy all weapon carriers before the gas-mask advert and then destroying all the billboards will reward you with the Riot gunpod-carrying mook. Taking the alternate route by destroying Greif's floater unit can award you with a second Riot gunpod. Later, assuming you take the alternate route, the pallette-swapped Drache can spawn an even rarer Juno autocannon.
Suicide Mission: The Astraea/Endymion are on kamikaze missions to basically damage the forces of the Earth as much as possible before dying — which makes sense when you think about it. It IS a SHMUP, you're probably going to die at least once in the gameplay itself. The only problem is,you actually survive.
Taken Up to Eleven again in the Stage 7 before the final boss, where every enemy carries two gunpods at once.
Theme Naming: Almost all of the Mooks (including bosses) are named in German. In particular, some of them are named after World War 2 tank naming convention in German. An example would be Stage 5's miniboss and boss, SPKB-06 Ausführung A "Gestell" and SPKB-07 Ausführung D "Dürer".
There was a time, in the era of great chaos, when the Earth and the Moon were at war with each other. A daredevil from the moon piloted a bizarre aircraft. It was feared, and because of its shape, called...Einhander.
Unperson: In the ending, both Selene and the Earth Forces delete every record of the protagonist's existence and endeavours. Only "those who actually fought and were wounded in the war know the name of 'EINHÄNDER'."
Forever War: Neither Earth or Selene want an end to the conflict. It's like a page from 1984: the perpetual war is what allows leadership of both nations to remain in power and maintain the status quo. This the reason why the Einhander's actions are erased from history and Selene wants no survivors from their suicide missions to return home (they know the Earth isn't a paradise at all).