Mappy English translation
マッピー
A small but tidy patch that replaces the only Japanese screen in the Game Gear version of Mappy, its options menu, with an English one.
What's translated
Most of the Game Gear Mappy already uses English, so there was only one thing left to fix: the options screen, which was drawn with kanji. Maxim Zhao's patch replaces it with an English version, making the whole game readable without Japanese.
Versions
The first release in October 2016 simply swapped the graphics on that screen. Version 1.1, out a day later, draws a completely custom options screen without the space limits of the original, and also fixes and adds the cartridge header data.
Under the hood
The creator's repository is meant as a worked example for other hackers too: it shows how to replace a screen's drawing code with custom code, build the patch with the WLA DX assembler, squeeze data into unused space with off-the-shelf compression, and more.
Playing it
Apply the patch to your own copy of the Japanese cartridge following the instructions in the repository.