I didn't realize you could hit the boxes into the furnace until about my third attempt, and I don't know why I'm shoving things in the furnace or cranking the thing, or how much to do either of those things, but dang does this game look nice. I do wish that there was more of an indication of how well you were doing, how damaged your ship was, and how damaged the enemy's ship was, as it wasn't clear at all how well I was doing. Maybe an explanation of the different UI elements would help with that though.
Very good concept though and one of the best games I've played so far. I can't help but wish that this was multiplayer, with different people cranking, feeding the furnace, and shooting the enemies. Seems like it'd be super fun