SA-1 Starfield (Murmuration)

128 dots in Lissajous sine patterns computed by the SA-1 coprocessor

What You'll Learn

• SA-1 computing 128 sprite positions per frame using sine harmonics
• I-RAM as a shared buffer: SA-1 writes positions, SNES CPU reads them
• Procedural sprite generation (no graphic assets needed)
• Depth illusion via 4 brightness palettes cycling across sprites
• Synchronization protocol between SA-1 and main CPU
• Running SA-1 code from I-RAM: copy it there, keep it position-independent

Build & Run

cd $OPENSNES_HOME
make -C examples/chips/sa1_starfield

Then open sa1_starfield.sfc in luna (or any SNES emulator).

What to Observe

• 128 dots moving in smooth, coordinated flock-like patterns
• The pattern resembles a murmuration (starling flock)
• 4 brightness levels create a subtle depth effect
• All math computed by the SA-1, from I-RAM: at boot it copies its loop and sine table there, so it does not share the ROM with the main CPU (~10.7 MHz; ~8.5 MHz when built with make clean && make SA1_CODE_IN=ROM — see the SA-1 tutorial for the measurement)

Modules Used

Module	Purpose
console	System initialization
sprite	OAM management
dma	DMA transfers
background	BG configuration
input	Joypad reading
sa1	SA-1 coprocessor driver