Ach,
Very cool game, and it had a great look to it.
I really admire the fact that you threw the player into a situation in which they were forced to learn controls right off the bat and included graphics to support this - I hate it when games either require you to take a tutorial, utilize a really long and drawn out tutorial, or expect you to know the controls without at least giving you some kind of hint. You used more of a classic way of looking at learning to play games that I think a lot of developers and players have lost sight of.
One negative thing I noticed about the game was that the sand made some levels easy in comparison to earlier (and easier, as one should assume) levels. The level where there are vertical platforms leading up to the exit door and the player is expected to wall jump in between them to reach that door, for example, is made very easy if the player just waits for the sand. I can see how levels like this are very appropriate for Lava Mode, though, which I feel is a great idea.
Cool shite!