Thanks for checking it out! I'm glad you had fun and enjoyed it. Yeah, those moving guys are tough to get around for sure. I agree that if I set up aiming with the mouse, it would have most likely made it a bit easier. One tip for taking them out, is that they can actually shoot each other if they are lined up properly, but it's hard when they are moving to random locations.
As for getting repairs, aside from restoring some energy between each wave, you can press the 'P' key to pause the game and select the retreat button (as long as you have >25% of your energy remaining) and it will send you back to base. When you are there, you can select the Merchant button, and that will subtract from the funds you've collected and add to your current energy.