A 3D computer game (for DOS, ie PC) by Ken Silverman (who later went on to create the BUILD engine), with graphics by the demo group Future Crew, it was released as shareware on January 1, 1993, and then re-released by Epic Games in March that year.
It is similar to Wolfenstein 3D: the game world is made up of squares, all of the wall tiles are the same size and the graphics are all sprites. The graphics look slightly amateurish nowadays, but are perfectly adequate.
In the typical shareware fashion, the first episode ("The Search for Sparky") was released freely, and the second ("Sparky's Revenge") and the third ("Find the Way Home") were only available as part of the registered edition.
The aim of the game is quite simply to complete each level, you do this by basically just walking through, avoiding being killed by enemies, killing enemies yourself, and collecting keys to open doors. Pretty standard fare, even for modern FPSs, which shows you how little progress has been made.
Weapons, which had unlimited ammo, consisted of red jelly, bouncy bullets and heat seaking missiles. At the start of the game you only had red jelly, the other two weapons were obtained during the progress of the levels. You could also collect up to 4 "lightnings", which made bullets go progressively faster.
Other items you could collect were extra lives, coins and keys and gems (which gave you the equivalent of several coins), as well as several items to restore your health - apple (1x), meals (2x) and first-aid kits (2x).
There were slot machines scattered around the levels, which you could use to gamble coins, and soda machines, using which you could buy items with your coins. You could also use magical items, which only operated for 30 seconds of time after picking them up. These were purple potions (which hit monsters with increased power every time they were hit by a bullet, reduced damage to you, and allowed bullets to travel through walls), green potions (which reflected bullets back at enemies), grey cloaks (which allowed you to walk right through monsters and bullets) and blue cloaks (which made you destroy enemies upon contact).
There were lots of different types of monsters, mostly mythical creatures, although the most entertaining one was simply a moving hole. The only way you could tell the different between a moving hole and a normal hole (other than that it moved) was that the moving holes had glowing red evil eyes. The only way to get rid of them was to simply lead them to a normal hole and make them fall down it (the eight balls were also only destroyable using this method, and it was easy to get rid of the frozen ghosts this way).
It was released as freeware on November 16, 1999 as is available from http://www.advsys.net/ken/klab.htm, however you should be warned that you will probably have to use Mo'Slo, as new computers have severe issues otherwise.
System Requirements: 286+, VGA, 365k of RAM. Supports: Adlib/SoundBlaster, Joystick/Mouse/Gravis Gamepad, and EMS or XMS memory to increase the speed of the game.