Would be great if there would be a harder difficulty level. The campaigns and challenges (I did those one after another, one map at a time) aren't that challenging once you get a hang of the game mechanics.
It would seem that when you click to buy an upgrade for a level 4 tower, the ability you bought will be used throughout the map despite the ability to re-purchase it.
Going towards my 5th final boss fight, almost 50k gold on top of all upgrades, still 4 lives left....fun but I'm about to suicide just to end the grind
Maybe not a sequel in itself but a nice remake. Too bad it's ridiculously easy, even at impossible; the first one actually required time to get the hang of in to win.
Note to editor: I will keep killing the penguin in a fiery crash by ramming him into the ground at 1,000-1,500MPH until I get the ROB medal. It's the only thing I have left (including achievements) and it's annoying. No more penguins will have to be victims of your low random odds at supersonic speed if I get what I want. Their deaths rest on your shoulders, monster.