Visually this was excellent. I really liked the design of most of your robot army. I particularly liked how the sharpshooter looked when upgraded.
I thought the Stalin and Molotov-tossing bear were a little...eh? I would much rather have seen a Westinghouse reference or a Mark Twain reference (or simply, more machines.) I would have liked to see other upgradeable units as well, and perhaps more in-depth upgrades.
The path system was interesting. It kind of picked a middle ground between a single linear path and greater overall control. I dunno why greater overall control wouldn't have been as good, aside from somewhat balancing out the tunguska towers and UFOs' longer range, but whatever, for this type of game it's quite enjoyable. I thought it strange that the boss at the end was a mobile enemy, and yet aside from the ones that wait along the path and latch onto you there aren't any others. Patrolling enemies might have added to this as well, particularly robots of a more Edison-esque design.
The final battle, well...it just wasn't challenging or interesting. I ended up with three bears in no time and killed Edison accidentally while trying for 100% completion, then it just kind of...ended? Coulda done with a cinematic or something to tie it up nicely.
All-in-all it was fun, and if you made another I'd definitely play it.