· Commodore 64Mappy on the Commodore 64, with a REU
Mappy, the 1983 Namco arcade game, now runs on the Commodore 64. It is an unofficial, free port, and this time a stock C64 is not enough: it needs a 1 MB REU, Commodore's memory expansion, real or emulated.
Why the REU. Scrolling the house at sixty frames a second needs two screens, and those plus the program fill almost all of the 64 KB. The sixteen houses, the music, the screens and the bonus round live in the REU, which copies them into memory by itself, about ten times faster than the processor.
True to the arcade. The engine follows the original game's rules and was checked against more than a thousand recordings made in the MAME emulator. Every bug the testers reported I hunted down frame by frame in VICE.
On the game's page there are a video and an article that explain it all, with charts. Download it from itch.io. Thanks to AlexNinja71 for the testing.