So, it looks like the game is faster than when you posted in the discussions. Assuming I'm not misremembering, this speed is much better. The progress bar is also nice to have, though I think marking where the enemy waves are in the progress of the level would've also been nice.
The only complaint I have is that level 3 can be beaten by just sticking one boulder in the path of the enemies. It'd be a lot more work, but I think that design would need the enemy ai to be able to evaluate paths with boulders are being higher cost but with the enemy being able to break the boulders if there's not faster way. Levels 1 and 2 are good though.