Really great work so far! Here are my biggest concerns:
An "instant restart" button would be really suited to the trial-and-error gameplay you're going for here. For example, pressing "R" to reload the level whenever I screw up and lose the ability to progress would be really great.
I also felt that movement was a little floaty and my character felt too fast and uncontrollable. Tweaking some numbers there might help with the overall feel of the game.
That aside, this is really good stuff! I love the way you're iterating on the core mechanic of decaying tiles.