Hang-On (Enhanced 1.1 Hack):

What is changed?

• Redrawn splash screen
• Redrawn title screen with animation
• Now there is in-game music, with SFX
• All music has been rearranged and made more similar to the original arcade music, using the original game’s music engine
• Redrawn motorcycle sprites, more similar to the original arcade art
• Opponents are different colours in each stage
• Redrawn background art
• Road and scenery colours changed
• Rearranged HUD to more closely match the arcade game
• Race start redrawn to be similar to the arcade game
• New checkpoint SFX and text
• Split times are shown at each checkpoint, with frame accuracy
• Motorcycle acceleration is now smoothly varying with speed
• High scores are saved to cartridges saves (where supported)
• The original game’s easter egg has something new…
• There is a hidden sound test

Technical notes

One of the goals of this project was to avoid expanding the ROM. As the original was very full, this was achieved with various space-saving measures – mainly recompressing all art with ZX0 compression, but also replacing some of the tilemaps and text used to draw the screens with compressed data. It was also possible to remove some space used by SFX (which now only use a single channel) and for computing the bike engine RPM (which was used only to control the engine sounds). Some other data was replaced with more space-efficient code.

It was also necessary to fully disassemble and understand the music engine in order to modify it as needed (and to replace the music). The final music is longer and more complex than the original, so it takes more space.

There is therefore, as a side effect, commented disassembly of much of the game’s workings, as well as some Python tools used to dump the game’s music and track data. Much of the disassembly wasn’t really needed for the hack, but it seemed a good idea to publish it all in case it is useful in the future.

Source is at https://github.com/maxim-zhao/hangon-sms-enhanced

AI disclaimer: an online LLM was used occasionally during development to help write Python scripts and to answer questions about makefile syntax. It was not used for writing Z80 code or to generate art or music.

Credits

Art, music, project direction

chirinea

Hacking, code

Maxim

Title screen art

badcomputer