Very nice game! It's always addictive to have some upgrades giving more and more power!
I have the feeling the machine "Magnemite"-like is a bit too powerful: as soon as you unlock it, it's quite easy to farm gold gears, so that you can upgrade it at maximum and you basically become God :D
When all upgrades are purchased, the game just becomes "click on the gray button on the bottom as soon as it appears", but it's still satisfactory to see our army of robots killing the invaders :)
I stop at wave 35 because I have some work to to do x')
I could definitively play more with more upgrades and treats!
A leaderboard on Wavedash would be cool also, this kind a game fits well for that.
Anyway, very well done!