Impossible Mission is a platform computer game for several home computers. The original version for the Commodore 64 was programmed by Dennis Caswell and published by Epyx in 1984.
Impossible Mission has the user play a secret agent - attempting to stop an evil genius. Professor Elvin Atombender is believed to be tampering with national security computers. The player must penetrate Atombender's stronghold, racing against the clock to search the installation for pieces which form a password, all the while avoiding his deadly robots. Once in possession of all the password pieces, the player must correctly assemble the password pieces together and use the completed password in the main control room door - where the evil professor is hiding. One finds password pieces by searching furniture in the rooms. When searching, one can also find "Lift Resets" and "Snoozes." They are used at computer terminals. The former will reset all moveable platforms, the latter will freeze all enemies in the room for a limited time. There are also two special rooms where additional lift resets and snoozes can be awarded for completing a musical puzzle.
The location of puzzle pieces, arrangement of the rooms and elevators, and abilities of the robots are randomly distributed each game, providing replay value. Caswell cites Rogue as his inspiration for the randomised room layouts.
The Commodore 64 version is notable for its early use of digitized speech. The digitized speech was provided by the company Electronic Speech Systems, who drastically raised their prices after Impossible Mission became a successful test case. Epyx did not deal with ESS again as a result. The digitized speech included:
- the player character's death scream as he falls into a lift shaft. This scream was later re-used in another game Beach Head II: The Dictator Strikes Back.
- Professor Atombender's opening line: "Another visitor. Stay awhile... staaaaay FOREVER!" Other prominent lines are his exclamation, "Destroy him, my robots!", a devilish laugh when the clock runs out and the game is over, and admitting defeat shouting, "No. No! NO!"
- a female voice saying "Mission Accomplished. Congratulations!" when the game had been completed.