Nice game :) I wished you used your "simple" aesthetics to give more informations two the player about which blocs are alternating ones (with grey for the walls and spikes that stay activated). Also, green is not a good color for a dangerous item. I would go for red spikes and green wall when alternating.
Still pretty neat and giving the taste of retrying and improving, just got stuck on a level with two yellow jumping pads on the left, I was not able to jump above the two last spikes near the exit.