Simulated Evolution on the PICO-8

2 days ago

The author was burnt out from previous articles and took a break to work on a simple PICO-8 project, porting Simulated Evolution.
The simulation was adapted from earlier C/assembly implementations into PICO-8's Lua dialect, with design changes such as using separate BORN and DIED tables for bug management.
To efficiently track and render plankton without extra arrays, screen memory was utilized as real memory by mapping a 150×100 world onto a 128×128 spritesheet using custom coordinate functions.
Scrolling was implemented easily using PICO-8's CAMERA and CLIP commands to handle the large world not fitting entirely on-screen.
PICO-8's 16-bit signed integer limit was circumvented by using its 32-bit fixed-point numbers and adjusting values, with bit shifts accommodating fractional values.
A Garden of Eden feature was added via the MENUITEM() facility for the pause menu, allowing toggling and simulation resets without rebooting.
Graphical data was generated externally with Python, though initial hex formatting issues corrupted map data silently; PICO-8's IMPORT command helped with spritesheet and label imports.
The simulation runs efficiently at 60Hz using only 60% CPU, but lacks custom seeds due to reliance on built-in RNG and no keyboard input for convenience.
The finished cartridge includes steganographically encoded program art, with source available on GitHub and added to the SimEvo project collection.

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