The resources coming in from the sides in a kind of queue system is a really great idea. However, the instructions were a bit unclear. Clicking an empty tile didn't create a drill, but pressing Space did - little things like that... I think it would've been better given the instructions incrementally as the player is playing, instead of trying to explain everything at once as half the screen is taken up my instructional text.
Still, I enjoyed playing it and is a great twist on the whole defence style game - good job!