Spectrumizing coins gives your weapon new abilities- (the bandit coin allows you to steal more things from the enemy, the healing coin heals, etc.) Just don't use the dark coin. It makes you sacrifice your own health to kill enemies. Not sure what the time coin does.
The time time coin will sometimes put your enemies into stop status. Your weapons can alos only hold so many of those coins, I think the max is 7 or 8. And if u try to put one on when it's full u'll lose all of the other coins that were on just to put that one on.
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