when u deselect a tower the price at the sell button remains, and I think it's good that u dont have the usual tower types, if u want those kinds just play something els, but I do agree that it's still a bit easy, u can create a killing ground at the beginning of the maps and easily get the perfect score
based on the theme uppgrades is maybe not the right way to go, perhaps military ranks instead, needs a sell button for towers. perhaps three different tiers, cell warfare, electric and army strong based on the different tower types, uppgrades that is.
Empyreal Destroyer
Dude! You just completed the Empyreal Destroyer achievement in Ether War and won the Empyreal Destroyer badge and 15 points!
got this in first game