SpectrEm
A ZX Spectrum. 48K, 128K, +2 and +3, with the ULA timed to the frame and a Z80 debugger beside the screen.
ApplEm
Cycle-accurate Apple II Plus, //e, //c and IIgs emulation for the Mac, with a debugger and profiler.
Things to play
Source
Everything here is on GitHub. These are the repositories without something to play in the browser yet.
RetroTech71 is Mike Daley's workshop. The machines here are the ones I grew up with, rebuilt in C++ and WebAssembly so they run in a tab; the games are excuses to learn how the originals worked. Nothing is sold, and all of it is on GitHub.