Re: Upgrades. It made sense to me. :) I like that research points carried over to other levels so I could plan ahead a bit. I found the upgrades very useful. Would have been nice to be able to but them in survival mode.
To the developer: I find that the survival mode becomes unplayable as there are too many enemies on screen around level 27. Granted, my computer isn't the most powerful here, but it's not that bad. I'd prefer they got harder with more hit points or faster or whatever, rather than more numerous.
 "Pawnbarian"){kind=icon}
 "NGU IDLE"){kind=icon}
 "Swarm Defender"){kind=icon}
 "Cruiser -Battleship 2"){kind=icon}