Well done! The gameplay works fairly well, though I quickly became overwhelmed by enemies, balancing the player's health and the energy needed to spawn boxes required more strategy than I was ready for on a late Sunday evening :P But it's definitely interesting and I might come back to it.
I didn't find much use for mines though which didn't seem to be worth the trouble in terms of damage vs energy cost.
The graphics and audio are both quite good and serve the gameplay well!