I found the jump mechanic frustrating, when trying to land on one-block platforms (as in 1-7). The jump difference between "tap" and "hold" is pretty much meaningless, at least in the levels I've seen so far. Often near the start of levels, the game ignores my presses of Z or Shift. When "auto-run" is on, holding Z should allow you to walk. R for restart should be respected on the end-of-level screen. The aliased font scaling on the end-of-level screen is particularly ugly. The level designs are interesting, but the poor platforming mechanics caused me to give up before the end of world 1.