Originally written in 1984 by Matthew Smith. This port is based on the original ZX Spectrum version, written in C and using the SDL2 library.

Game play is 100% identical. The original game had bugs which have been fixed, such as landing at the end of a jump into a solid wall.

Some subtle improvements have been made to make the game more enjoyable:

• Per pixel colouring. This eliminates colour clashing.
• 16 colour palette.
• 2 replacement character set fonts; one small, one large.
• The title and in-game music scores have been reproduced and are polyphonic.
• The sound effects are approximately the same as in the original game and include stereo panning effects.
• To give the music and sound effects a retro feel, a square wave generator is used to give it a "beepy" sound.

Cheat mode is activated just like in the orginal by typing the cheat code. Once activated, switching levels is as simple as typing the level number followed by ENTER. Levels lower than 10 do not need to be preceded by a zero, i.e. 01 or 1 has the same effect.

The original game needed a "code card" to start the game after loading. This was an early attempt at copy protection. If you don't want to experience entering those codes, press any key during the "JetSet Willy Loading" sequence.