This was addicting but I got too frustrated to keep playing. My key presses would not register when the controls were just about to change (or maybe it was after they changed), which prevented me from making tight saves. I'm more certain this behavior was an intended feature rather than a glitch, and thus I admire your attempt to prevent players from making a move they didn't intend, but I wish you did it in a way that didn't disable movement all together. After all, my response to a key appearing not to work is to press it again, which would result in the same consequence had my input not been disabled.
the game was otherwise super tightly designed and hard to put down. Great job!