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Corridor 7: Beta Invasion

In a time of cold and lonely nights in December 1993 when people were hunting demons on phobos, there were still more demonic aliens hiding in the dark. Well hidden, they rarely made it out of the shadows of thy Doom.

Roughly 2-3 months before Doom and Blake Stone would be released, the development of Corridor 7 had started. We are entering the year 1994 and there is a thirst for more. Soon after, Corridor 7 was released.
It is not unlikely that due to the late start on development things were more rushed. Rushing things seemed to be generally a Capstone Software trend.

This was still many months before Operation Body Count was even in development. For some reason many websites tell you that Body Count was released first, which makes as much sense as terrorist-trained killer rats.

This is a short summary of an early build (JAN 1994) of Corridor 7.
Trying to be more less accurate, there might be some errors and some sections are incomplete. The audio, especially the sounds, still need a closer look as well as the AI and small gameplay adjustments.

The pre-release was ready about 3 months ahead of the full release and it was 3 months after project started, according to design documents by Les Bird (Lead Programmer). Even being in the middle of development, this version is for the most part what you can see in the final release.

This demo/beta is dated at beginning of January of 1994 and was released on a German Shareware games disc collection. It’s called “202 Games Spezial” and published by Mustang. It might be dated to September 1994 (long after the final release) and if so then either someone sent them the wrong files or they got it from some mysterious source.

Apart from that there is another early (beta) version, a demo, a full floppy release and the final CD release.
The version covered here should be the earliest existing version of the game.

A brief overview of the releases:

  • BETA-DEMO / early JANUARY 1994
    • 3 levels 
    • 131 textures 
    • 440 sprites (178 of those being Wolf3D) 
    • 77 images (vga) 
    • 37 adlib sounds 
    • 37 pc sounds 
    • 46 digi sounds (46 from Wolf3D) 
    • 2 imf music tracks in audiot + joesnd file

  • BETA-DEMO / end of JANUARY 1994 
    • 1 level 
    • 136 textures 
    • 459 sprites (62 of those being Wolf3D) 
    • 84 images (vga) 
    • 34 adlib sounds 
    • 34 pc sounds 
    • 11 imf music tracks
  • DEMO / middle of MARCH 1994 
    • 1 level 
    • 136 textures 
    • 416 sprites 
    • 39 images (vga) 
    • 64 adlib sounds 
    • 64 pc sounds 
    • 64 digi sounds 
    • 8 imf music tracks

  • FLOPPY RELEASE / end of MARCH 1994 
    • 36 levels 
    • 136 textures 
    • 598 sprites 
    • 55 images (vga) 
    • 83 adlib sounds 
    • 83 pc sounds 
    • 83 digi sounds 
    • 34 imf music tracks
  • CD RELASE / JULY 1994 
    • 59 levels 
    • 256 textures 
    • 858 sprites 
    • 72 images (vga) 
    • 100 adlib sounds 
    • 100 pc sounds 
    • 100 digi sounds 
    • 34 imf music tracks + 4 audio CD tracks

Click to Enlarge


Let’s start with something more familiar, like Wolf3D. The beta version still has some Wolf3D assets sitting in the files and the dog is even running around in the second level. Below is a picture showing some of them, but not all the frames and most of them are using the wrong palette.
Most curious part is one of the death frames having a grey sphere. Possibly an early test for future concepts?

First, a rather boring and tiny detail. Left are the original keys/map for the hud display and on the right you can see the ones from the beta. There are small differences for the color cycling. 300% zoom for better viewing.

Now it’s time to face some walls. There are several walls in the final release that already existed in the earlier version, but with minor changes to them. Nothing too drastic to see here.
There are a few details which got changed like the word “EMPTY” on the ammo machine. The crates seem to stand out more in the beta due to the contrast and the differing brown shades in the palette. Several textures also have been adjusted just for the color cycling.

Left is the full release. Right side shows the beta version.

Now to the wall textures that didn’t maket the cut into the full release and only exist in this early version.
Slot-wise they haven’t been really added or removed. Most of the graphical frames seem to have already existed at this point. For example at the spot in the data file where you can find the metal bar gate, you will find an animated door in the later full release. They kept the layout of most things and mainly swapped the graphics themselves to something similar. 

The sprites have a similar twist to them like the textures. There weren’t many drastic changes between versions. The death animations are still bit rough and one of the weapon items got split into 2 items. 

Next are objects that don’t show up in the final release. Not too many but few interesting ones like the shades pick up or a crystal pillar.

The beta contains 3 odd sprites. The ceiling grass/slime was used for the hanging corpses in the end. Depending on the editors you use you may or may not see some glitched pixels on the other 2. If you encounter either the plant or table it will freeze the whole game. 

The biggest difference is probably that the Probe (flying eye with turrets) used to be a robotic drone. It might be the “Tracker” enemy concept mentioned in the design documents.

The weapons are all smaller and more simple compared to the final release. Projectiles already existed in this early version. Most made it to the final release but got changed drastically, with the assault rifle/M-16 changed the least and the plasma launcher the most.
The knife is mentioned in the design document as “Bayonet” but didn’t make the cut. 


The game itself plays and looks pretty much like it would months later. Nevertheless, there are differences present in the pre-release version:

  • Files have the WL6 extension and use the same files+names (e.g. VSWAP.WL6) WOLF3D has.
  • Many of the 3D image/intro renderings (used in intro/menus) are already existing but used in different ways.
  • Credit sprites still lack shading. 
  • Rocket launcher item is 1 pixel higher. 
  • It has the tentacle skull boss (unlike the official demo) but it’s not very well animated. 
  • Credits screen doesnt mention music. It has 1 programmer and 1 artist less on it. Also got note “Graphics Engine by Id Software”. 
  • Tile8s are broken.
  • The palette has some small changes in the brown color row.


  • There is no intro story or any highscore screen after the title.
  • Menus are different and incomplete. 
  • Save/Load Game menu isn’t accessible.
  • Music volume slider in the menu seems to be working reverse for digitized music. Maybe a reason the music got removed.
  • Has option for digitized music which uses the “joesnd file” by Joe Abatti. 
  • The digi music format is in 9000 Hz 8-bit mono. 
  • The menu doesn’t have any digitized music track. 
  • Digitized music pauses when digitized sounds play. The music might be made of short samples. 
  • One digitized track uses the death scream of the player. 
  • The 3 audio tracks are quite different and seems more groovy or experimental. Maybe closer to Body Count’s audio CD tracks. 
  • The digi music might have been pushed back due to technical difficulties or the problem of storing enough songs on a floppy disk. 
  • Some of the audio tracks were remixed for the later CD release.
  • There are 46 digi sound files in the VSWAP but they are all from Wolf3D.
Click to Enlarge


  • There are 2 rooms in the first level that can freeze the game. 
  • Demo (after intro) runs into one of those rooms and freezes. 
  • F7-F9 screws up statusbar and borders. 
  • Window size menu has the wrong size when entering it from max viewsize.
  • Enemies inside masked doors can’t be damaged. Operation Body Count has same issue. 
  • DosBox freezes right at start of the level if cpu cycles are set too high. The game also freezes when lowering the viewsize in lower cpu cycles. So if the game reaches a certain framerate it dies. Different side effects in real DOS not excluded.
  • Masked walls clip through masked doors while opening/closing (was not fixed in later versions). 
  • Masked walls can also disappear entirely.


  • Automap has a different color theme. There is an item to unlock the whole map. Uses ‘M’ key instead of TAB. 
  • Purple floor color instead of grey as in the final version.
  • Gunfire doesn’t affect floor/ceiling shading. 
  • Shading is darker and more intense on ceiling. 
  • Gun bobbing is less extreme and in a different style but still depends on run button. 
  • Weapon bobbing of the knife is quite more extreme and looks like constantly stabbing something. 
  • Just pressing “run key” doesn’t make you slide around like in the full version. 
  • Weapons and HUD overlay “info” bars on bottom if window size is on max. 
  • Ammo for weapons #3 and #4 regenerates fast automatically. 
  • The player has lives and is thrown back to the menu after getting a glitched score screen.
  • level1diagnostic debug line works but needs alt+lshift+backspace like wolf3d. 
  • TAB+L debug code makes wall shade flicker like gun fire but in a darker variation. 
  • TAB+T shape test debug code is still there but some sprites can crash Dosbox. 

There are some dotted bars on the bottom of the HUD which seems to give away some clues about the game. Possibly raycasting checks.

  • White bar goes up when a masked door is visible. The closer the bigger the bar.
  • Yellow bar. No idea so far.
  • Green bar seems to be for the walls. 
A small difference in memory usage. Notice the broken Tile8 border


If this version was released to the public on purpose then it was probably intended for only the first level to be accessible and playable. There are two more in the files, accessible through debug commands.

Level 1: 

  • Actual demo level that shares a few similarities with the first level of the full release.
  • There are 2 rooms on the map that can freeze the game. At start behind at the windows to the left and one on east side after a glitching wall. Possibly caused by 2 corrupted sprite objects.
    You can prevent that by walking backwards around the critical sprite.
  • It is possible to complete the level, and says that the demo is over.

Level 2: 

  • A big square room that seems to have formed the base for a lot levels.
  • It has animated masked doors with the wrong graphics.
  • It got a massive room that creates slow downs.

Level 3: 

  • Several rooms but seems to be rather a dev map and consisting of test rooms 
  • It features the sun glasses item and automap item. 
  • Has 2 Wolf3D dogs running around. 
  • Possible test rooms for animated walls and their speed.
  • There is a wall that isn’t in full release as test for the health chamber (flashes yellow and does a 180 degree spin).
Click to enlarge


Here are some screenshots in case you are tired of the messy article for a messy game. The statusbar looks especially rough.
Overall, the design and style of the game stayed pretty much the same until the end of development. They mainly kept adding gasoline to the fire over the next months, fixing some things but mostly more enemies, weapons, graphics, music, and levels were added. The additions didn’t expand on the game much, and quality remained the same for the final releases. If you have never liked this game then any of the other versions won’t fill you with happiness either.

BETA 1 / early JANUARY 1994

BETA 2 / end of JANUARY 1994


There are still some details missing in this long corridor made out of text but as in the style of the game this is incomplete and possibly buggy.

Doomed from the start, the game has some pretty cool ideas and a great atmosphere. Sometimes it helps a game to be rough around the edges to give it a character. Take some DNA of a Xenomorph, rip out Wolf3D’s gut, add the spirit of Doom and you get this piece of entertainment.

If you ever feel bored, there are more than 7 corridors to get lost in. Give it a try or just go play Body Count!

Download the pre-release of Corridor 7 here.
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