I'm a big fan of tower defense games! And i liked yours, i liked the audio and the game loop! Even the graphics, i understand it's AI generated but at least it fits.
I made three runs and i found two main problems to this game. The first is that i went attaching the gears to the walls by pure luck, i had no clue the first run then noticed it. The second is that robot ai is a bit wacky, i managed to connect the miner and while the big ones were attacking my "engine" it was collecting gold x.x
It's a something i would like to play with some work :)
ps: The wood gears breaking is an EVIL mechanic, i like it too :)