The music and sound is nice. I love the art style. Don't let any negative comments get you down about the game play. The game has a high learning curve, but it's actually really fun. It's a push/pull game between attack and defense. My favorite abstract board game, Tzar, is set to the same theme. You have to keep moving and decide every second on whether attacking spawns or cooling pylons is better. You can't win without doing both and the challenge is finding the balance between the 2 for each round.
It took me about 3 tries to figure out what I needed to know at any given moment in order to complete the main game. For anyone feeling overwhelmed you either didn't efficiently use down time to cool your crystals and the wave is going too long (the longer the wave goes the worse the spawns get), or you didn't kill spawns at a far enough distance and they swarmed your crystal (once about 2-3 are in position to attack, just give up on that crystal and either prepare for next wave or defend a secondary one if it's a 2 crystal wave).
It's pretty addicting once you hit a rhythm. Of course I'm also a glutton for difficult tower defense games so this hit the right buttons for me. My personal requests would be some type of indicator when I'm close enough to the water to refill (you have to keep moving, and fidgeting with the water refills became difficult in late waves), spawns leaving the minimap faster after they die (I became very paranoid of things I had already killed attacking the crystal or a flier spawning I didn't catch), and some built in way to knock everything off the crystal and buy me time to recover when **** hits the fan (Finding powerups to do something like this takes too much of my attention away from defending. My suggestions are a once per game burst so you have to question if this is the wave you NEED it, have the water knock back enemies but not hurt them, or for risk/reward you can explode your water container, but can't use water for the rest of the round while it recharges/rebuilds.)