If you feel the game gets too hard in the later levels, you can have 'infinite' energy by button bashing your mouse. If you click really fast, the enemy still gets stunned, but your energy almost doens't deplete.
Please vote up if you think this tip is any good. :-)
The "Destroy Boss in x minute bla bla"-challenges can be easily beaten by summoning as many Shell Shouter Guardians as you can and flying into the middle of the boss, then just stand still! Galactus-a-gogo!
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