@Savetz recently interviewed me about how I programmed a star cluster simulation in valFORTH on my Atari for a science fair project in 1986.
The interview is forthcoming. In anticipation of that, I have attached the software for you to play with. You do not need to know Forth to enjoy this, but you do need to be patient. It's slow.
a) For the demo I do in the interview: mount "ClusterDemoTypeDOIT.atr" on your real or emulated Atari 800. Boot, and type "DOIT".
What you are seeing is two views of 3-D space. On the left, the Z axis is pointing straight at you. On the right, the X axis is pointing straight at you. For more details, watch or listen to the interview 🙂
b) To explore further, mount "Cluster4thFiles.atr" as drive 2 and reboot. Type the following (ignoring my parenthesized comments):
MTB ( empty buffers; seems to be important for the following to work )
0 82 C! ( narrow the left margin for readability )
DIR 2 ( show DOS-format D2: disk contents )
CLUSTER ( hold START - or click it rapidly in emulation - to exit )
PRINT D2:CLUSTER2.4TH/N ( to see the actual source of the simulation, already loaded )