JSW Central - Resource Centre for ZX Spectrum games based on Manic Miner and Jet Set Willy game engines

Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines

IV. Jet Set Willy 128 (JSW128)

Games using John Elliott's JSW128 game engine for the 128K Spectrum

19. Jet Set Lemmy

Authors: Francisco Urzúa (Lemmy Lemming) and Daniel Gromann

Year: 2025 (v. 1.0.0-1.1.6)

Reissued: 2026 (v. 2.0.0)

Language: Spanish

Jet Set Lemmy was Francisco Urzúa's first attempt at editing JSW. He described it initially as "a silly little Jet Set Willy hack." The first release of the game, launched in March 2025 using the JSW128 engine, included rooms from the original JSW, modified to varying degrees.

Daniel Gromann found some critical bugs in v. 1.1.6 of the game that made it impossible to complete. His communication with Lemmy soon turned into a collaboration in which both authors added more things to the game. With time and further work, the game was modified so much that version number 1.2.0, under which Lemmy wanted to release the next version of the game, became obsolete and number 2.0.0 was adopted for the release of the hugely modified file that was finally released to the public in August 2026. The info that follows refers to v. 2.0.0.

The game features 128 rooms. Of these:

57 are versions of rooms from the original JSW, modified by Lemmy;
34 are brand-new rooms created by Daniel;
24 are brand-new rooms created by Lemmy. Some of these rooms were inspired by other games - please see the Readme for details;
6 are versions of rooms from the original MM, modified by Lemmy;
2 are versions of rooms from JSW II;
2 are versions of rooms from Pothole Pete, a 1984 game for the Memotech MTX by Antony Butterfield and Jim Wills (Continental Software), recreated by Lemmy with permission from the original authors;
2 are versions of rooms from Son of Pete, a 1985 game for the Memotech MTX by Antony Butterfield and Jim Wills (Megastar Games), recreated by Lemmy with permission from the original authors;
1 is a version of a room from Willy New Mansion.

Sprites used in the game are a mixture of sprites from the original JSW (mostly modified by Lemmy), the original MM and JSW II. There are also sprites from other games (Pothole Pete, Son of Pete, Henry's Hoard, Technician Ted and games by Adam Britton, Carl Paterson, the DrUnKeN mAsTeR!!! and Hervé Ast). Furthermore, some sprites were designed by Lemmy and some by Daniel.

The game is unprecedented in terms of in-game music variety. It features a title-screen tune and 25 in-game tunes, all custom-coded by Lemmy and Daniel in the JSW128 music format and most never used in any JSW game before. This unprecedented variety of music is possible thanks to a technical solution whereby in-game tunes are stored in Memory Bank 4 (normally used for room data), and the tune for a given room is copied to a buffer in Memory Bank 0 upon entering the room and played from there.

The game utilises Hacklevel 9 of the JSW128 game engine.

Number of edited rooms: 128

Number of rooms accessible without cheating: 128

Number of items to collect: 256

Bugfix needed after original release? NO

Spare lives at the start: 7

Completable without loss of life? YES

Starting time: 7:00 am

Best documented completion time with no unnecessary loss of life: No walkthrough is available publicly yet.

Download links

Homepage	The game's home page on JSW & MM Community

Original release	Version 2.0.0 of the game, including the game file in TAP and TZX formats and the Readme in English and in Spanish

Direct game download	Game file of v. 2.0.0 in TAP and TZX formats