+ to solve level 11: in day to day programming there is a trick for swapping two values without using a third variable, the same trick can be applied here. The only hint I can give you is: use arithmetic plates
You don't need a third variable? I mean, i've heard of the XOR swap, but your game doesn't have an XOR operation. But i found a different solution anyway, so...
EDIT: Nevermind, i was thinking of a different puzzle.
This game kinda reminds me of
brainfuck. I like that this is a game that exercises skills useful in programming.
Having all the symbols unlocked right from the beginning is something i think puzzle games usually try to avoid. It was confusing at first which pieces were necessary to solve the first puzzle. You offer an instructions menu; it would be helpful if that was either partially included in the dialog at the beginning of the level, or in any way referenced that it exists in at least the first level's intro.
At the same time, i understand that not having each piece unlocked at the beginning would lower replay value (optimizing for speed and memory).
EDIT: You should require more than one run to test if the program works. I solved at least one puzzle just by random chance.