I love the game, but you should be able to do a newgame+(basically the same concept that was in 3), and the Premium Content should give a special key item that unlocks a new world area, like a DLC.
I honestly agree with the others about the backup thing. If you're going to make something like this, either increase the playing field or increase the number of characters that can be used to 5-6.
You should make it so things that are oxymoronous, like Thunder Jellyfish or Thunderbirds, have 50% resistance to the type they're weak to but the element they are.
I also would like to know where the key locations are, because I can't for the life of me find a copper key to unlock the Danger room after I've flicked all the switches.
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