What a cool idea out of the theme. I was pleased to see the design space explored in the last level, where you need to hold opposite directions down to stop yourself, but keep the movement for later. I wish you had more levels doing that.
You could create a lot more design space and levels exploring it with the right supporting mechanics. A timed obstacle could force you to stop, the same way I mentioned previously. Perhaps a pickup that could refresh your key presses? There's a lot of potential!