Im playing through this right now and have experienced a strange sensation:
Sometimes when I die holding left, then let go of left and restart, the kid will have moved one frame to the left. This even happens when I let go of left like 0.3 seconds before pressing r. I tested this quite a bit and was able to recreate it easily.
Aside from that the game is awesome, I played it til 2nd boss so far und will continue tomorrow most prob.