Notes

The 🌀 key is called the Koru key.

To reset the machine hold down Escape-Alternate-Koru.

F0 performs a non-maskable interrupt. To register the key, set the NMIADD system variable to call this routine:

; // F0 pressed
usrnmi:
ld a, $ff; // use a byte to set key state (0 is off)
ld $<addr>, a; // write state to arbitrary address
reti; // return from interrupt