In game achievements that award money or bullets or a new gun would be cool. With things like "Get a Skill to 100", "Kill 200 Enemies in the Arena", "Kill 1000 Enemies", "Reach Day 10". You know, stuff like that =)
Under the tool tip for the eye tower it tells us that it gets the same upgrades (Inferno, Greed, Volcanic) as the tower of fire but in the start menu the upgrades for the Eye tower are Radar, 3 Eyed, and Chain lightning. Not that big of a mistake but should be fairly easy to fix!
I think if you beat a level on advanced you should get another copy of the item it gives you, because when you play it again it clearly states that the item is still a reward for winning.
On the fourth section of the adventure mode you can bypass the level 5 gate by falling from higher up. I did this on accident and now I am stuck behind the gate as I can't go back through from the other side because I am not level 5 yet. Please add a platform or something to block this from happening or let the character pass through the gate from the opposite side.
I don't know if this is on purpose but every time I get new upgrades in the store it resets all my points. It's not score crippling but it's pretty annoying. At least now that I have all the upgrades I hope it won't reset for no reason.
How are you supposed to get the mechanical orchestra thing to work? The little glowy thing that shows where patterns are indicates that but all it tells me is that it's missing parts.
Achievements are awesome in games. Good idea, I'll might consider adding that