sandworm

program space is an arbitrary sized grid the worm starts where you place the worm head @ as it passes over commands, they get moved to the back of the worm (also depending on the worm length) commands to change direction <>^v values get pushed to stack (eaten) when passed over, worm body length increases autosarkophagy/self-cannibalism is possible, cutting off the back of the worm (the lower part of the stack) and pushing the passed value to the stack (front of worm) conditional: pop then side/forward if top of stack is zero

commands

+- pop 2 values *, push sum/difference (uses the order they are popped, so `0 -` negates the top of the stack)
><^v change direction
0123456789ABCDEF push number to stack
/\ pop stack, reflect to the side if zero
? reads one byte of input
= duplicate top of stack
! pop and write output as ascii char
" pop and write output as number

• pop when stack is empty yields zero