This was the most fun I've had with any of the jam submissions so far! I got a serious case of the "one mores" and couldn't move on until I beat the boss and got a run that I was satisfied with. There are a lot of small design considerations that go into making an action game that's this irresistible, and you clearly know the recipe for that secret sauce.
Having the enemies spawn in designated and clearly marked locations makes the waves feel fair, and grouping those spawn locations together was a stroke of brilliance, as it created zones of higher risk and reward. Destroying the bots right as they spawn makes it so the batteries drop in a tight cluster for easy farming, but going to retrieve them is risky because an enemy could spawn right next to you without warning. The special shotgun blast attack encourages risky play as well because of the wide spread. It felt great to melt the boss' HP with 4 close-range blasts and then retreat back to safety. The camera's zoom level was also ideal for reading the action, and it subtly teaches the player the optimal distance for engaging enemies.
As far as presentation goes, the visuals were fun and distinct, like something out of a cartoon from the early 2000's. I appreciate that the UI elements occupy a small space- it must have been tempting to make them bigger because they're really stylish looking. Also, the music never got boring or repetitive even though I played for a good while. It does a great job setting the mood of the game and keeping the excitement up.
I don't have many issues with this game, but I'll say that the feedback for taking damage could be more clear. A prominent sound effect and some screen shake would do the trick. Also, making the camera pan based on cursor placement was a good idea, but the effect is disorienting and could be toned down a bit.
I'd love it if you dropped a downloadable Windows build, because I'll absolutely be revisiting Bots n' Batteries and the browser build's performance gets a little crunchy when the action gets hectic. Really great stuff, I had a blast with this one!