Here are some bugs i managed to see:
1: Towers on Highlands become less XP
2: While pressing quickly skill+LMB (e+LMB) it briefly shows the skill radius, but doesn`t cast it
3: Not a bug but the AOE Demon Tower is pretty useless, if you upgrade it to Max (Non-Stop Damage) it deals just no damage. Before max level it just doesn`t attack more than once on the same enemy.
this game is easy when you win it for the second time :) I will give you a tipp >> Music ON! The best tactic to win the levels with those invisible walls is, to jump over the wall at the beggining! It wins everyting :)