Crystal Quest Gg — Development skill for Claude Code

Crystal Quest — Game Gear port kit

A colourised Sega Game Gear conversion of the 1991 Game Boy version of *Crystal Quest*, produced as a **build kit**. The kit contains no code or graphics from the original game. `build.py` recompiles the game from **your own copy** of the Game Boy ROM and writes a `.gg` file.

python3 build.py "Crystal Quest (USA).gb"          # -> crystal_quest.gg

Requirements: Python 3.8+ and SDCC's `sdasz80`/`sdldz80` on `PATH` (any SDCC ≥ 4.0, the same toolchain devkitSMS uses). The ROM is checked against `rom_sha1.txt` (`Crystal Quest (USA).gb`, 32 KB, no MBC).

What you get

• The whole game, logic-exact. Every wave and every nasty type (play-tested up to wave 40, the highest the secret menu reaches), the bonus and time-bonus screens, the Hall of Fame, one- and two-player modes, the attract-mode demo, and the secret title-screen codes. The original SM83 code is statically recompiled to Z80, instruction by instruction, so behaviour matches the original rather than approximating it.
• Colour. A deep-space look in the spirit of the Macintosh original. Crystals are cyan, the ship gold, nasties red/green/purple, walls steel blue, text gold, the menu crystal clusters violet, and the title nebula blue. The game's own palette effects (fades, the smart-bomb flash) still work, because they drive the colour ramps.
• Sound. The Game Boy APU is modelled per frame (envelopes, length counters, sweep, noise, NR50 volume, NR51 panning) and played on the SN76489, with the Game Gear's stereo port carrying the original left/right routing.
• Full speed. No frame overruns in normal play, and 4 lag frames in 1,800 on a crowded wave 40.

Controls

Game Gear	Game Boy	In game
D-pad	D-pad	steer the ship
2	A	fire
1	B	smart bomb
Start	Start	start / pause
Start + 1	Select (+Start)	menu toggle; Down+Start+1 quits to title
Start + 1 + 2	A+B+Select+Star