Micro-8 is an 8-bit computer with a custom OS and a custom programming language called Lofi, along with a suite of examples, tools and utilities made available to help you create small 2D games and applications that run on real hardware. Based around an ATMega128 8-bit RISC MCU, it features, among other things, custom graphics and audio (on top of a genuine YM2612 chip) as well as a fully custom mechanical keyboard and 220 pages full-color printed manual. More details available on the web page.