Only realized later on what the mechanic was (red doors open when HP matches, yellow doors open when enough keys are had and uses up keys), feel like the challenge spike in level 2 was a bit too much though. Agree with comments below that a digital grid based movement would help things as the hitboxes on the spikes seemed a bit too big for comfort. Very interesting mechanic though and taking a hit to progress seems like something unexplored much in games!