Stay at Home Edition: Refraction for the Atari 2600

RetroChallenge 2018/04: Writing a proper Atari VCS / 2600 game

Refraction for the Atari 2600 (RetroChallenge 2018/04)
Accepting the processor clock challenge…

There’s a noble challenge, every programmer of self-esteem should obliege to at least once in a lifetime: programming a game for the Atari VCS, also known as “racing the beam”. In case you didn’t know, the Atari VCS (Atari 2600) has no video RAM and every line of raster image has to be composed on the fly. More so, you also have to maintain the vertical composition of the TV image, and there is no operating system, no ROM, just the bare metal machine and a trusty video/sound chip (TIA) to talk to. And there are only 128 bytes of RAM in total, already including the processor stack. To do this properly, it’s 6502 assembler once again, but this time every cycle counts.

Particularly, we do a classic two players console game with a twist. A classic game, like it was 1979, no additional hardware enhancements or fancy bank switching allowed. On the way, we learn about the Atari VCS and its hardware, and how to tackle the programming side of things. Moreover, there’s a tiny sprite editor for the VCS and even a synthesizer app to explore its somewhat unique sound generation. Also, it’s our first RetroChallenge project in color!

Start reading: “Refraction for the Atari 2600”…