Nice game, I thought to make one of this kind on tic80, but you already made it :). I like the move of the body, depending, on the head, I didn't thought to do such a move.
For information, you can, instead of calling sin/cos (adding subroutines and code to interpret, do this, this work on both Lua and javascript:
cos=Math.cos
sin=Math.sin
acos=Math.acos
Great code and piece of software else :).