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Having now played through the game in co-op mode I have to confirm that it is a LOT more fun in co-op!

I think it's mostly because the obnoxious i-frames the enemies get are mitigated somewhat and being able to do long chain juggles with a friend is suuuuuper satisfying, esp. on enemies that would lock me into unbreakable chains in single-player!

Revenge is sweet!