This was awesome! It took a bit of time to understand that I should mine the things that are on the way (even tho it's said at the beginning!), but once I understood that it started to get pretty fun!
I wish there was a way to defend your engine from getting hit besides just putting weapons around. Also, some kind of synergy between weapons positions would have been fun.
I really like the mining idea! It splits the player's attention from having to repair machines to go and earn enough gold to survive. And the fact that you actually have to click multiple times to mine a mineral pile means that you have to follow it with your mouse, so it's not as trivial and gets harder with the speed of the engine. A really clever way of making what could have been a very passive game into something very active.
Thanks for working on this!