It looks like the game was updated this week; some enemies seem to run through the maze and are not slowed down by the freezing tower (and no, these were no ghosts).
overall, the game is a bit too easy - the challenges are not really challenging once you get the right gear. I saved crystals until i got a bit more than 100 to create the gear. But great game none the less!
 "Prime World: Defenders"){kind=icon}
 "Sky Quest"){kind=icon}
 "GemCraft Labyrinth"){kind=icon}