Seems to be a bad memory leak or something. The higher the levels go, the slower the game loads and bugs start showing up. Like the Click to go to next level words show up over the puzzle.
@nevermath There is a reset button. You can then redistribute your points. Also.. some of you have a horse shoe stuck up your .. you know where... i have gold on everything, decided to go back and get 0/###. I have been playing for over 2 hours on the insane levels.. cant get 0 on any of the first 5.
clicking the Main Menu button (assuming it also pauses the game since there is a "return to game" link), the Next Wave timer still counts down. Upon returning to game, you will now have, depending on how long you were afk, all the waves it counted down, equaling instant game over.