CLK

Hatari is already excellent? https://github.com/hatari/hatari And there's also Clock Signal (CLK) "A latency-hating emulator of: the Acorn Electron and Archimedes, Amstrad CPC, Apple II/II+/IIe and early Macintosh, Atari 2600 and ST, ColecoVision, Enterprise 64/128, Commodore Vic-20 and Amiga, MSX 1/2, Oric 1/Atmos, early PC compatibles, Sega Master System, Sinclair ZX80/81 and ZX Spectrum." https://github.com/TomHarte/CLK

Also possibly of interest is CLK aka Clock Signal, an emulator that outputs a composite "signal" instead of pixels: > Consider an ordinary, unmodified Commodore Vic-20. Its only video output is composite. Therefore the emulated machine's only video output is composite. In order to display the video output, your GPU must decode composite video. Therefore composite video artefacts are present and correct not because of a post hoc filter but because the real signal is really being processed. https://github.com/TomHarte/CLK

There's some ugliness to acknowledge here in the fact that user remapping of controls is not yet implemented. That being acknowledged. The easiest place to hack would be https://github.com/TomHarte/CLK/blob/master/Machines/ColecoV... — change the Input('#') to declare a key you prefer (e.g. Input('-'), and then change the corresponding case statement within the block starting on line 62. If you follow that approach, you'll have modified the ColecoVision so that it declares a joystick with a minus key rather than a hash key, which it's hard to imagine the host binding getting confused about. If you'd prefer to look at the other side of the interface and figure out why your host isn't posting '#' properly then you'll see the SDL fragment at https://github.com/TomHarte/CLK/blob/master/OSBindings/SDL/m... — it takes the first character of wha

Phosphor-decay simulation isn't new - xscreensaver has had it for ages. What is new, and slightly mindboggling, is that they're going below "treat display as pixels and post-process them" and generating an actual PAL signal. I've not checked to see whether they're keeping that in frequency space or actually emitting samples at some rate above 4MHz. But it's an interesting approach. https://github.com/TomHarte/CLK/blob/master/Outputs/CRT/CRT.... seems to be well-commented.

There's an Electron/VIC20/2600/Oric emulator that does this too: https://github.com/TomHarte/CLK - looks authentically horrid and it's got that somewhat elusive 50Hz feel. (Not many 50Hz Electron games, though! Firetrack is one.)