Construction upgrade is still slightly bugged, while the cost reduction does apply, the hotkeys don't work until you have enough money to have bought the tower or trap at full price.
It's too easy to spam RP from massively clicking an item and skip.
The skip should only pop up after a second or something, and the overuse penalty needs to increase depending on how frequently the item's been used recently.
Warp turtles are really annoying. They seriously need to warp at least three times less often, and be edible while fading in/out of warp.
Also, even stupid creatures know how to avoid obstacles. At least make the penguins get another target if they find themselves stuck on one.