||This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: does not meet project guidelines. (July 2009)|
|Release date(s)||1984: Commodore 64
1985: Acorn Electron, BBC Micro, ZX Spectrum
1986: Amstrad CPC
1988: Sega Master System
2007: PS2, PSP, DS, Wii
2010 Oric Atmos
Impossible Mission has the user play a secret agent who must 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 selected 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.
Impossible Mission had only two types of enemies. The first were the robots. These had a cylindrical main body, much like R2D2 or a Dalek. Their defense was high voltage: their bodies were electrified, and some were able to use a short range death ray. According to the instructions, the robots used linear induction motors to move around, and different robots had different features enabled. Some would be stationary; others move in patterns, and others would specifically hunt the player. Some would shoot and others would just try to ram the player. Some had to actually see the player, and others knew where the player was at all times. The robots' abilities were randomized, so that a room that was easy to explore in one game might be much more difficult in another.
The second enemy was an enormous hovering electrified ball. Much rarer, most of these would chase the player (with a couple of exceptions). They were inspired by the Rover "security guard" from the Prisoner TV series. While it would be affected by a "snooze," unlike the robots it still had a high voltage when disabled. The hovering ball would disappear if it came in contact with a robot. In certain rooms, it would be possible to stand on a movable platform with the hovering ball directly underneath, and push the ball off the bottom of the screen, only to have it re-appear at the top.
The player has six hours of game time to collect 36 puzzle pieces. Every time the player dies, 10 minutes are deducted from the total time. The puzzle pieces are assembled in groups of four. The puzzle pieces overlap, so three pieces can be assembled before the player realizes he must start over. Pieces may be in the wrong orientation, and the player may have to use the horizontal or vertical mirror images. Additionally, the puzzle pieces are randomized in every game. A completed puzzle forms a nine letter password which allows the player to reach Professor Atombender.
The most obvious winning strategy is to avoid dying as much as possible, while systematically searching every object in every room of the base. In many cases, it is much safer to leave a hard-to-search object behind, remembering where it is, and come back to it when a snooze pass is available to you. With six hours of game time, a patient player will spend a good deal of time winning snooze passes from the musical puzzle rooms, rather than risking death and wasting time. A successful player will also manage to memorize the layout of each of the rooms, the location of Atombender's door, as well as the orientation of the puzzle pieces.
Ports and sequels 
Though originally developed for the Commodore 64, Impossible Mission was ported to the Apple II, Atari 7800, ZX Spectrum, Acorn Electron, BBC Micro, Amstrad CPC and Sega Master System. Not all of the ports had the same features as the C64 edition, such as speech.
The NTSC Atari 7800 version has a confirmed bug that makes the game impossible to win; it places some of the code pieces underneath computer terminals, which the player cannot search (since attempting to do so will access the terminal). The bug was fixed in the PAL version. Rumors of a bug fix for the NTSC version were put to rest when Atari formally announced the retirement of the Atari 7800 on January 1, 1992.
The NTSC Atari 7800 version was converted from the Commodore 64 version by Computer Magic, Ltd. Contractors Brian Richter started the conversion, with Arthur Krewat finishing it. Krewat states that he was able to complete the game in the final version he gave to Atari, but that somehow either means Atari used a previous development version for the cartridge, or they tried to shrink the memory footprint so that it would not require as much static RAM in the cartridge. Atari themselves tested the game and approved it, paying Computer Magic for the final product. Krewat is adamant in stating that the final version supplied to Atari was bug-free. Krewat is working on resurrecting his source code of Impossible Mission for the Atari 7800 as of December 2008 and has found that the code he supplied Atari is identical to the ROM image available on AtariAge.com. Work continues to determine how the bug came about.
The sequel, Impossible Mission II, followed in 1988. It further complicated the quest with new traps and items. Elvin's stronghold also grew in size, now divided into a number of towers which the player had to traverse, all the while picking up pieces of the password (an aural one this time around).
A 3D sequel was planned as a launch title for Epyx's "Handy" system which eventually became the Atari Lynx. The game was eventually renamed ElectroCop and the released version had no apparent connection to the original Impossible Mission, but appeared similar to earlier version of the game in which it still bore the name.
In 1994, Impossible Mission 2025, the final game in the series (so far), was released for the Amiga. It kept the same idea as the previous games, and mainly featured updated graphics and audio, as well as allowing the player to choose between three different characters. The game also contains the original Impossible Mission.
In 2004, Impossible Mission was one of the games featured on the C64 Direct-to-TV.
Impossible Mission was to be remade for the Nintendo Game Boy Advance by Oceanic Studios under license from Ironstone Partners in 2004. The development deal seems to have been put on hold.
Developers System 3 are revamping Impossible Mission for the Sony PSP, Nintendo DS and Wii (it is often mistakenly believed to be the first WiiWare game, but is a budget title released on the 31 August in the UK). In the US, the Nintendo DS version was released exclusively at Gamestop stores by Codemasters and the Wii version was released in March 2008.
See also 
- Edge issue 167, October 2006; "The making of Impossible Mission"
- Dennis Caswell interview from MayhemUK Commodore 64 archive
- "Top 50 Games of All Time". Your Sinclair (Imagine Publishing). November 2004.
- Post on World of Spectrum forums
- System 3 official website of the revamped game
- Epyx returns on Wii, PSP, DS; retrieved from Gamespot UK
- System 3 website of revamped Wii game
- Gamestop's Impossible Mission Page. Retrieved on April 22, 2008.