The upgrades descriptions could use some improvement. I still have to guess what half of them do. Does the zombie damage increase make them DEAL more damage or TAKE more damage? I assume it increases how much damage they do, but I don't KNOW. The description/tooltip text just repeats what the zombie icon already says, rather than clarifying. + zombie damage, 3 heads
For the weapons the more expensive one is obviously better, but it's not like the description tells me anything about its damage or fire rate or... anything useful. Right now the description box could be absent entirely and it'd functionally be the same.
And besides being required, what's the point of the boss energy upgrades? Delay zombie summoning ever so slightly?