CTHON is an old-school First-Person Shooter developed and published by Gravity Games, originally available via Itch/io
and later published on Steam via its "Greenlight" system on March 17, 2017. In essence, it is a Roguelike take on Wolfenstein 3-D, with sprite-based objects and purely horizontal movement.
It is the 24th Century. Humanity has only just begun to expand to star systems beyond our own. The player takes the role of a surveyor for a company called Sigma Corp. While passing through the Epsilon Eridani system, you receive a Distress Call from the remote Pythos colony. Given that you're on the only ship in range, you decide to investigate, only to have your ship fried by an EMP and crash-landed. What you find on Pythos is an Elaborate Underground Base crawling with cybernetic horrors and strewn with mysterious artifacts. Your instincts scream for you to run, but something is drawing you deeper into the base...
This game provides examples of the following tropes:
- Advanced Ancient Acropolis: The third and final tileset is called The Hive, a dark and ugly area that seems to have living doors and has been turned into a Necropolis, with the cybernetics and remains of the Phleb entombed in the walls, staring you down with dull red eyes.
- Anti-Frustration Features: You have the option of saving and exiting between levels if you'd like to take a break. If for whatever reason it crashes during the subsequent level, you'll be able to continue again from the start of that level- though it will be re-rolled.
- Ambiguous Ending: Whether his death was planned or not, or whether its even going to stick, killing Cthon was just the beginning. The player character is whisked away to who-knows-where, without seemingly any hope of ever returning. And this was destined to be so, if the epilogue is to be believed.
- Artificial Zombie: The enemies of the game apparently all some form of this. They are controlled via their still-functional cybernetics by the same signal that disabled your ship. It's also mentioned that the energies of your weapon disrupts this signal, which is the only way to "kill" them.
- Big Creepy-Crawlies: One enemy is a large spider-like creature.
- Color-Coded for Your Convenience: The color of a weapon or Ion Armor lattice indicates how much power it has. Blue for no extra power, level 1 is purple, level 2 is red, level 3 is dark yellow, and level 4 is bright yellow with green trim.
- Character Class System: You have a choice of three classes at the start of a run. Each is more effective with one of the game's three weapons.
- Cybernetics Eat Your Soul: A strange case. It's clear that the Phleb had no rational reason to build Cthon, the culmination of their technology and were promptly annihilated by him. The player is essentially forced to use their technology to upgrade themselves to have a chance of success, which the game specifically notes may be molding you into one of Cthon's champions. Whether this trope is being played straight or not depends on whether you were meant to slay Cthon or not.
- Deflector Shields: Ion Lattice Armor, which creates a force field around your character. It seems to be a repulsion field than a standard deflector, however, since it provides constant Damage Reduction as long as its powered instead of stopping X number of shots before dissipating and recharging.
- Elaborate Underground Base: The first area, the Facility, is a network of cramped rooms and corridors, which, thanks to this being a Roguelike, have nothing resembling a sensible layout. Considering the scientists were apparently drawn to Pythos by Cthon, this might be entirely justified. The Temple and Hive areas are similarly nonsensical.
- Eldritch Location: Cthon's chamber doesn't look like it belongs in this reality, with a lot of Sickly Green Glow going on. The game itself notes you're probably not on Pythos anymore by that point.
- Emergency Weapon: The Blade consumes no ammo and can always be used. However, if sufficiently upgraded it might potentially be a viable primary. It helps that it can hit enemies slightly further away then some of them can.
- Energy Weapon: All your weapons are this. The Cannon is a Plasma Cannon, the Blade is a Laser Blade, and the Launcher uses something called "Shock Bombs" that generate brightly-colored explosions.
- Equipment-Based Progression: The Upgrade Artifacts are your only means of increasing your abilities, and thanks to Randomly Generated Levels, whether or not you get enough of them to complete a run can be something of a Luck-Based Mission.
- Equipment Upgrade: All three of your weapons can be upgraded via some Upgrades you find, and their sprites actually change in appearance to reflect which upgrades, as well as how many of a certain type, are active. The corners of your HUD also change to reflect your level of armor.
- Flunky Boss: Cthon itself is a huge, green-and-silver heart in the center of a big room who sends evil robots after you.
- Game-Breaking Bug: Until a recent patch, a sound issue related to Windows 8 and 8.1 could cause the "Wyrm" enemies' projectiles to crash the game.
- Gameplay and Story Integration: Acquiring and using the Upgrade Artifacts gives you greater odds of reaching Cthon, in a manner not dissimilar from the Phlebs' journey to building him in the first place.
- Ghost Planet: Pythos has been dead for a very long time. A human colony being wiped out was nothing new.
- Grenade Launcher: The launcher.
- Hearing Voices: The player character can hear them once they reach The Hive. It's mentioned these are the laments of the Phleb, and non-hostile.
- Hoist by His Own Petard: You can very easily damage and kill yourself via poorly-placed Shock Bombs. In some cases, it may be advantageous NOT to use Grenade Splash Radius upgrades if you have them.
- Ikea Weaponry: Upgrades to your weapons appear on them. For example, activating more coolant pumps increases the size of the drum on the side of the cannon, and more Power Divertors create a glowing power core in the center of their respective weapon (or changes your lightsaber's color in the case of the blade). It's also possible to turn the cannon from a "pistol" into a shotgun depending on how many Diffusion Arrays you activate.
- Late to the Party: As per standard, there's no one left alive on Pythos by the time you get there.
- Limited Loadout: Averted in the case of your weapons: There are only three in the game: The Cannon, the Blade, and the Launcher, and you begin with all three. Your upgrades are another matter, however.
- Heart Container: One type of Upgrade Artifact is expressly this.
- Inventory Management Puzzle: You begin the game with only a single inventory slot for upgrades, one upgrade, and unit of power to use that upgrade. You must find "Framework Nodes" to increase your slots and "Circuitry Cores" to increase your max power, allowing you to use more upgrades at a time. You'll find a few of these simply lying around in the open, but chances are you will either need to hunt for the secret areas which just might contain more, or purchase them from a Workbench at a cost of 50 nanites for a Node and a staggering 100 for a Core, the two most expensive purchases in the game.
- Mechanical Abomination: Cthon himself. Or itself. Who knows. The Phleb seem to have treated him with some measure of Machine Worship... until they actually built him.
- Nanomachines: Used here as money, for purchasing items from the occasional automated vendor: Workbenches provide new inventory slots and the power to use them, Forges allow you to buy and sell upgrades, and Dispensers sell health kits and ammunition.
- One Hit Poly Kill: The Cannon can be upgraded to shoot through enemies.
- Permadeath: Dying ends your current run.
- Precursors: The Phleb, Cthon's creators, and his first victims. They are noted to have made incredible advances in cybernetics before their fall.
- Randomly Generated Levels: Each floor's layout is randomized, including placement of enemies, items and shops. Notably, doors that look like they lead somewhere may just lead to dead ends... though this does not preclude the presence of secret areas.
- Ruins for Ruins' Sake: The second of the three tilesets is a crumbling temple complex that the human colonists of Pythos built the Facility directly on top of.
- Survival Horror: The game has hints of this. Your starting movement speed is visibly much slower then games like Wolfenstein 3-D or Doom, you can't take many hits, pickups are uncommon and increasingly rare as you progress, and enemies are relatively few in number but hit very hard, putting the player on edge and forcing you to conserve health and ammo. However, if you are lucky or thorough enough to find and use enough upgrades, you become faster, more durable and lethal... though so do your enemies.
- Spread Shot: The Cannon can be upgraded to fire multiple projectiles in a horizontal spread pattern. The snake-like "Wyrm" enemies are also capable of this.
- Upgrade Artifact: Lying about the levels are individual cybernetic modules that can upgrade your weapons and defenses. These are stated to be the most physical and immediate byproducts of the Phlebs' advanced science.
- The Undead: See Artificial Zombie above.
