MicroMan

You are MicroMan, stuck inside a computer. You must run, jump, and shoot your way out. Along the way are cannons, a variety of mechanized enemies, ladders, invisible bricks, three different weapon upgrades, a super jump ability, a shield, moving platforms, platforms that fade in and out of existence, transporters, a mirror room and bottomless pits.

MicroMan was made by the author of WAP (Windows Animation Package) in order to demonstrate the abilities of that WAP Windows 3.1 game engine. The game was so popular that the author went on to make the shareware release of The Adventures of MicroMan, which has completely new level designs.