Beautiful graphics. Although the scale is tiny, the colors are lavish, and each area looks quite distinct. The controls are also smooth, with unobtrusive wall-scaling. Respawn times are mercifully brief.
There are some SFX, but not many, and no music. Remember that a little bit of effort with sound goes a long way--it always helps with immersion.
The main mark against the game is that death is extremely frequent, and always one-hit. It takes quite a bit of skill, and a large number of deaths, to get more than 3 or 4 screens into the game. I think that there could have been a more gradual ramp in difficulty.