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                                    |                                                   |            
                                    |                   Jet Set Lemmy                   |
		                    |                                                   |
                                    |                     v. 2.0.0                      |
                                    |                                                   |
                                    |        by Francisco Urzúa (Lemmy Lemming)         |
                                    |                                                   |
                                    |                and Daniel Gromann                 | 
                                    |                                                   |
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"Jet Set Lemmy" is a game for the ZX Spectrum inspired by Matthew Smith's classic game "Jet Set Willy" (Software Projects, 1984). It uses an extended 128K game engine created by John Elliott. It can be played on a real ZX Spectrum (128K or higher), on any of its modern clones or on a computer, game console or another device using a ZX Spectrum emulator.

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I. Game history

Francisco Urzúa (Lemmy Lemming) created "Jet Set Lemmy" in early 2025. He released v. 1.0.0 of the game on Jet Set Willy & Manic Miner Community on 4 March that year. He followed it with public releases of improved versions 1.0.1, 1.1.0, 1.1.5 and 1.1.6, the last one on 13 March.

Daniel Gromann playtested v. 1.1.6 and found some critical bugs in it 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 the passage of 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 on 28 August 2026.

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II. Instructions

Guide Jet Set Lemmy to collect all of the 256 flashing items scattered around the game map so that Maria will disappear and he will be able to reach his bed. You need to do it before 1 a.m. Avoid the moving and unmoving guardians, as well as the stationary nasties, which may kill you, as will a fall from an excessive height.

Use O-left, P-right (or a combination of keys from the top row of letters) and SPACE, or any of the letters from the bottom row, to jump. A-G pauses the game, H-ENTER/RETURN unpauses it (as do the movement keys) and also toggles the music ON/OFF.

Pressing SHIFT and SPACE at the same time abandons the current game (showing the Game Over screen and then returning to the title screen). Pressing these keys after the game has been completed takes you straight back to the title screen.

Both cheat modes present in games using the JSW128 engine work in "Jet Set Lemmy", but they are activated in rooms with different technical numbers than in the original "Jet Set Willy 128", and the passwords are different.

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III. Credits, acknowledgements and thanks


1. Game engine

The game uses a 128K game engine known as JSW128, created by John Elliott as an extension of the original 48K engine.


2. Rooms

The game features 128 rooms. Of these:

57 are modified versions of rooms from the original "Jet Set Willy". All of them were modified by Lemmy.

6 are modified versions of rooms from the original "Manic Miner". All of them were modified by Lemmy.

2 rooms are modified versions of rooms from "Jet Set Willy II". One of them was created by Lemmy and one by Daniel.

2 rooms are versions of rooms from "Pothole Pete", a 1984 game for the Memotech MTX by Antony Butterfield and Jim Wills (Continental Software). They were recreated by Lemmy, who also secured permission to use them from the original authors.

2 rooms are versions of rooms from "Son of Pete", a 1985 game for the Memotech MTX by Antony Butterfield and Jim Wills (Megastar Games). They were recreated by Lemmy, who also secured permission to use them from the original authors.

24 rooms are brand-new rooms created by Lemmy. Among them:
2 rooms were inspired by "Donkey Kong" (1981, Nintendo).
2 rooms were inspired by "Pac-Man" (1981, Namco).
1 room is a memorial to one of Lemmy's Tamagotchi virtual pets.
1 room was inspired by "Lemmings" (1991, DMA Design, published by Psygnosis).
1 room was inspired by "Technician Ted" (1984, Hewson Consultants).
1 room was inspired by "Pitfall!" (1982, Activision).

34 rooms are brand-new rooms created by Daniel.

1 room is a modified room from Daniel's game "Willy New Mansion" (2004; Special Edition 2016).


3. Guardian sprites

Sprites used in the game are a mixture of sprites from the original "Jet Set Willy" (mostly modified), the original "Manic Miner" and "Jet Set Willy 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, Hervé Ast and the DrUnKeN mAsTeR!!!). Furthermore, some sprites were designed by Lemmy and some by Daniel.


4. Music

The title-screen tune was coded by Lemmy. It is a rendition of "When I'm Sixty-Four" by The Beatles.

The in-game music comprises 25 tunes, all custom-coded in the JSW128 music format and most never used in any JSW game before. These tunes are based on existing tunes.

Some were coded by Lemmy, and these are typically tunes used in various computer games and media: "Lazy Bones" ("Lazy Jones"), "Star Dust" ("Lazy Jones"), "The Wall" ("Lazy Jones"), "Spy vs Spy" (Cartoon Network's MAD version), "Spy vs Spy" (Nick Scarim, First Star Software), "Anitra's Dance" ("Mountain King", C64), "Living on the Ceiling" ("Lazy Jones"), "Popcorn", "Humoresque" (two versions), "Eggie Chuck" ("Lazy Jones"), the "Jet Set Willy II" CPC theme and "In the Hall of the Mountain King" ("Mountain King", C64).

Other in-game tunes were coded by Daniel and are typically tunes from old, popular Polish songs ("Dzisiaj bal u weteranów", "Oj, bieda, bieda wszędzie", "Bando, bando", "A ty maszeruj, maszeruj, głośno krzycz", the medley "Gdzie strumyk płynie z wolna/Zaszyła sobie nitką") or tunes from old American songs and movies ("When the Saints Go Marching In", "Rawhide"). Daniel also coded the tune from "Hey Nanine"; a version of the Russian folk song "Коробе́йники", widely known as the Tetris theme tune; an excerpt from Frédéric Chopin's Piano Sonata No. 2, known as the funeral march (Marche funèbre/Marsz żałobny); modified, extended versions of the in-game tunes from the original "Jet Set Willy" (i.e. "If I Were a Rich Man") and "Manic Miner" ("In the Hall of the Mountain King").

This unprecedented variety of music was possible thanks to code written by Daniel, which implements the following mechanism:

In-game tunes are stored in Memory Bank 4, starting at #C000 (normally, the data of rooms 128-191 are stored in this memory bank). In addition to its usual components, each tune is preceded by two bytes of information about its length. Offsets #EE and #EF in each room's data point to where the tune to be used in that room is stored in Memory Bank 4.

When a room is loaded, the corresponding tune is copied from Memory Bank 4 to a music buffer at #B400 - #B5FF in Memory Bank 0. Since the length of the tune is defined at the start of the tune data, only the corresponding number of bytes is copied. No tune reaches 512 bytes in length (if any of them did, the buffer would have to be bigger), and the value #FF at #B5FF is never overwritten, serving as a termination mark for those channels that are unused (in the JSW128 music format, each tune can have up to three channels; not all tunes in "Jet Set Lemmy" use all three channels).


5. Screens

The loading screen was designed by Lemmy.

The pre-title screen was designed by Daniel, who also wrote the code that implements this extra feature.


6. Font

The font was designed by Lemmy.


7. Development tools and resources

The game was created using John Elliott's excellent JSW Editor (JSWED, http://www.seasip.info/Jsw/jswed.html). John's adjacent ropes patch (new) was applied in the game.

Richard Dymond (SkoolKid)'s complete JSW disassembly (https://skoolkid.github.io/jetsetwilly/) was instrumental in applying technical modifications to the original game code.

Norman Sword's optimisation of the Game Over sequence was applied in the game.

The Binary Hex Converter (https://www.binaryhexconverter.com/) was the standard tool used to convert values back and forth between the decimal and hexadecimal systems while introducing changes to the game's code.

Claus Jahn's ZX-Modules (formerly at http://www.zx-modules.de) were very helpful in creating the game, especially ZX-Paintbrush for the loading and pre-title screens, ZX-Editor for the BASIC loader and ZX-Blockeditor for producing the final TAP and TZX game files.

Jonathan Needle's Spectaculator (https://www.spectaculator.com/), Fuse (https://fuse-emulator.sourceforge.net/) and the ZX Spin emulator (https://www.zophar.net/sinclair/zx-spin.html) were used to playtest the game.

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IV. Internet links

JSW Central (https://jswcentral.org) is a comprehensive website dedicated exclusively to ZX Spectrum games using Manic Miner and Jet Set Willy game engines and their various minor mods and versions. It includes an up-to-date, complete list of Spectrum games created using the MM and JSW game engines, a chronology of their development, individual pages for all games and versions, including download links and screenshot galleries, and other resources.

The JSW Central YouTube channel (https://www.youtube.com/@jswcentral) contains video walkthroughs of MM and JSW games for the Spectrum, showing games completed as smoothly, elegantly and efficiently as possible, while aiming to achieve the best completion time (in JSW games) or the highest score (in MM games), with no unnecessary loss of life.

Jet Set Willy & Manic Miner Community (https://jswmm.co.uk/) is currently the best place for Willy-based discussion, game development and fun.

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V. Final remarks

We hope you will enjoy playing "Jet Set Lemmy" v. 2.0.0 as much as we enjoyed creating it.

The game can be completed without losing a single life. If you need some assistance, POKE 35899,0 will give you infinite lives. However, saving and reloading snapshots on an emulator or using the Rollback feature is a more elegant way to complete the game and will be more effective if you come across a multiple-death scenario (getting killed repeatedly upon entering a room).

You can contact Lemmy at lemmyscoolemailaddress@gmail.com or fran5678can on Discord, and Daniel at jetsetdanny@yahoo.com, with any feedback or questions related to "Jet Set Lemmy". It will be very rewarding for us to know that you have played the game, so please do let us know about it - even without any specific comments! For anyone designing free games, there is no greater gratification or encouragement than knowing that someone else has played them!

Play, enjoy, and let us know what you think of the game!

Lemmy & Daniel

28 August 2026