The only upgrades I'm aware of are the ones at the bottom of the screen -- a shield, water?, an arrow, etc They turn orange at some point if I click on them. No idea what that does.
I can deploy things?
1. I did not know what to do. It looked like I could buy upgrades like a typical incremental but nothing seemed to do anything useful.
2. I reckon as that line moves back and forth, it's closer to whoever is losing. I saw that the blue guy started taking damage (or at least, explosions were happening). It wasn't clear what I could do about it though.
3. Nope. Everything.
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I am trying again now and I see that if I click an "upgrade" the blue outline goes away and coins go down. So, that seems to do something. Not sure what though.
I would be fine with tooltips over the buttons as a start, just to be like "this is X and it costs Y".