*---Alright, first of all, the fact that you have lives makes zero sense, since everything you do is reset every time you die anyway (which I don't think should be the case, by the way; only when you hit Shift). There's no reason to care about losing your "last life". Puzzle games really don't need 'lives' anyway, unless you wanna make the player tear their hair out.
*---Like someone mentioned, the 3D looks nice, but it makes the two dimensional movement unwieldy and inaccurate. Either make the character move entirely freely and smoothly, or make him move in an obviouse blocklike pattern. The whole slow-walking tap-the-key-and-he-takes-several-step s-forward makes things tough. I hate when games do that. That make any sense?
*---Other than these things, the first 11 stages were fine, especially the last couple, which were fun and interesting to figure out.
*---But then came the first boss! It seemed like it was gonna be a cool chase until I realized that dying once brings me all the way back to the beginning. I suppose that would be okay if the stage wasn't entirely based off of trial and error alone. You almost *have* to die and memorize what to do, because the level consists of pushing up against the border of the level, turning and diving underground, hoping you made the right choice. If you didn't, you die. Start over.
*---Like the guy below me, I quit right on that level after I kept dying near the big cabbage patch after the maze part. For multiple reasons, that one part was extra annoying. Not in a challenging way. Just poorly designed.
*---The game looks like it got a lot of love in it, and it's interesting, definitely. Like the others say, you're on the right track. You just need to tweak this game some to make things work.