Overview
Corridor 7: Alien Invasion is a sci-fi first-person shooter developed and published by Capstone for DOS PCs in March 1994.
Set in futuristic 2012, the game takes place underground in a top-secret U.S. facility known as Delta Base, where a team of scientists brought an alien artifact from Mars into the lowest-level laboratory "Corridor 7". After radiation testing causes the artifact to open a vortex that allows an overwhelming amount of aliens to invade through it, a lone Special Forces marine must infiltrate the facility to destroy the artifact and stop the invasion.
The game was built on the Wolfenstein 3D engine, similar to their other game at the time (Operation Body Count), and was originally released in floppy disk format. An enhanced CD version was released on May 6th, 1995, containing more weapons, enemies, and levels, as well as added multiplayer and redbook audio support.
A sequel to this game, called Corridor 8: Galactic Wars, was under development using the Build engine, but was cancelled when Capstone went bankrupt. A prototype of the game can be found online.
The game later received a digital re-release via Steam by Ziggurat Interactive. on August 6, 2021.
Gameplay
Corridor 7 plays like traditional first-person shooters of the early 90s. One key difference is that the player must kill a certain number of aliens per level in addition to finding the exit for each level. The difficulty choice not only determines the number of aliens spawned, but the number of aliens required to finish each level.
- Corporal - Fewer aliens than normal. Only 10% of aliens must be eliminated to finish the level.
- Lieutenant - 75% of aliens must be eliminated to finish the level.
- Captain - All aliens must be eliminated to finish the level.
- Major - More aliens than normal. All aliens must be eliminated to finish the level.
- President - Only available in the CD version. Similar to the Major difficulty, only it features a customizable randomization factor that scatters all the items in the level.
The original version contains 36 levels, with 6 of them being secret levels. As the player makes their way through the campaign, the architecture becomes more alien-like and stronger aliens appear more frequently. The CD version extends the campaign with 10 additional levels that take place in the alien homeworld, as the marine chooses to enter the vortex to take the fight to the enemy rather than simply destroying the artifact. It also adds 8 deathmatch levels for use in multiplayer games, one of them based on the first level of another popular game.
Multiplayer in the CD version can be played in both regular deathmatch and team deathmatch. Because of the limitations of the Wolfenstein 3D engine, the firing animations always face forward. Players can choose between the standard marine or one of the aliens, which all have unique speed and health stats.
Visor and Proximity Map
The player's marine is equipped with a special visor that is capable of both infrared vision, which is used to detect hidden enemies and traps, and night vision, which is used to illuminate dark areas. Both special vision modes drain the player's visor battery over time, which can be replenished using wall-mounted dispensers.
In addition, the player can toggle an automap (or "proximity map") that shows a limited-range view of the map layout as well as nearby enemies and proximity mines. Hidden areas and certain enemies cannot be shown on the automap. In rare occasions, players can find a Floor Plan item that shows the entire map regardless of player position. Playing in the Corporal or Lieutenant difficulties automatically grant the Floor Plan at the beginning of each level.
Items and Interactions
Wall-Mounted
- Security Computer - Terminals that either grant the player Blue Door access, grant the player Red Door access, or alert nearby enemies to the player's presence. While it is unknown from the naked eye which computer does what before using them, they can be examined beforehand using infrared vision.
- Medic Pack - Grants 25% health. Must be interacted-with twice: once to open the blast shield and once to use the Medic Pack.
- Ammunition Bay - Grants 50 rounds of standard ammunition.
- Visor Battery - Fully replenishes the visor battery.
- Health Chamber - Replenishes health, while leaving the player vulnerable for a short time. Each chamber has a limited amount of health (up to 100%), and players can use part of it to reach their maximum and then use the rest of it later.
Pick-Ups
- Alien Charge Pack - Grants 100 energy for alien weapons. Can be dropped from certain enemies.
- Proximity Mines - Grants 25 proximity mines.
- Body Armor - Grants 200 armor points, which absorb part of the damage taken from enemies. Can be stacked multiple times. The Corporal difficulty grants one set of Body Armor at the start.
- Floor Plan - Increases the range of the proximity map to show the entire floor. Removed when exiting the level.
- Adrenaline Boost - Raises the player's maximum health up to 400%. Removed when exiting the level, along with excess health.
- Ammo Pack - Rarely found throughout the game, this item increases the player's maximum capacity for standard ammunition. Collecting one brings it up to 700, while collecting two brings it up to 999.
Weapons
The original game includes five weapons at the player's disposal, which use one of two types of ammo: standard ammunition and alien energy charges. Players start with the Taser and the M-24 C.A.W. with 100 rounds of standard ammunition.
- Taser - Standard security sidearm with limited range and very slow rate-of-fire. Despite its weak damage output, it requires no ammo.
- M-24 C.A.W. (Standard) - Standard fast-firing assault rifle that is optimal against weaker enemies. Also known as the "M-24 Close Assault Weapon".
- M-343 Mini Gun (Standard) - Prototype slug shotgun with rotating barrels, able to deliver powerful long-ranged blasts with a slow rate-of-fire. Also known as the "M-343 Tribarrel Power Blaster".
- Alien Dual Blaster (Energy) - Twin-barreled fast-firing alien blaster. Functions similar to the M-24 C.A.W., and is optimal for conserving standard ammo.
- Alien Plasma Rifle (Energy) - Alien projectile launcher that fires large plasma balls that explodes upon impact, damaging all enemies within its blast radius.
The CD version added three new weapons:
- Stakeout Ithaca Shotgun (Standard) - Standard pump-action shotgun that, despite being slow-firing, is much deadlier at close ranges. Also known as the "Assault Shotgun".
- Alien Assault Cannon (Energy) - Quad-barreled fast-firing alien blaster. Functions similar to the Alien Dual Blaster, with a faster rate-of-fire.
- Alien Disintegrator (Energy) - Powerful alien device that vaporizes every enemy in front of the player, at the cost of its ridiculously-high energy consumption.
In addition, players can collect and use proximity mines to lay traps for enemies. Up to 25 mines can be carried at one time and each mine are placed using a separate key (M). Players must be careful not to trigger the mine themselves or be close to one when it detonates, at it deals a very significant amount of damage in its blast radius. They are shown in the automap as red flashing dots and can be detonated from a passing Plasma Rifle projectile.
Enemies
- Animated Probe (400 pts.) - Tend to patrol their routes prior to being alerted.
- Bandor (500 pts.) - Can ambush the player by morphing from common everyday objects (such as chairs and filing cabinets).
- Ailoprobe (100 pts.) - Very weak on their own, but usually travel in packs.
- Eniram (1000 pts.) - Can ambush the player by remaining invisible to non-infrared vision when not firing.
- Eniram Boss (2500 pts.) - Boss enemy. First found in Level 5.
- Mechanoid Warrior (2500 pts.) - Boss enemy. First found in Level 10.
- Tymok (2500 pts.) - Boss enemy. First found in Level 15.
- Solrac (2500 pts.) - The leader of the invading aliens and the final boss of the standard campaign. It also tends to jumpscare the player throughout the campaign as hallucinations.
The CD version added the following enemies:
- Tebazile (10000 pts.) - The leader of the alien forces and the final boss of the extended campaign. It morphs into five forms throughout the boss fight: first in its natural form, then as the Eniram Boss, then as Tymok, then as Solrac, then back in its natural form.
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