Aesthetics are excellent. Simple yet appealing.
Audio is well fitting. The music loop is a little too short, but it didn't bother me too much.
You have made one fatal mistake in your design, in my opinion. And that's the addition of the timer restart. The game damn near forces failures and constantly changes the rules on you. That's fine. What's not fine, is that you expect me to restart the game from the beginning only so that I can eventually have another crack at the puzzle I'm actually struggling with, simply because I don't have sufficient time to think it through. I think the timer should have been for another mode, or simply force the level to restart. Certainly not the entire game to game over.
This ruined the experience for me.
The theme was hit intelligently and effectively.