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You can spam a boss over and over to get really powerful and negate the difficulty of the main game. I only did "Single Stage" on the same boss twice to see if it would indeed work and it did indeed, but certainly this isn't the intent of the design?
Well, experience gained seems to be lost after playing single stage, but upgrade points do accumulate.

So, whether grinding on single levels is intended or not, >something< is wrong one way or another :D
Post edited October 23, 2018 by vealckowsky