Congratulations! You just won the Spectral Selection Badge and 30 points! Really not that difficult. The bonus levels were challenging until you find the early openings.
to cast spells all you have to do is switch to your equipped spell using Q and E, like it says in the bottom left corner of the game screen. (same with melee)
as stated the song is Mad World, a cover of the Tears for Fears song, performed by Gary Jules and Michael Andrews. While receiving much credit for the song Jules only sings in it. Andrews composed and plays piano.
 "Earn to Die"){kind=icon}
 "Tentacle Wars"){kind=icon}
 "colorfill"){kind=icon}
 "Stick War"){kind=icon}
 "Medieval Rampage 2"){kind=icon}
 "Bounce 1.9"){kind=icon}
 "Fantastic Contraption"){kind=icon}
 "Neverending Light"){kind=icon}
 "The Majesty of Colors"){kind=icon}
 "Joe the stickman"){kind=icon}
 "Mad World"){kind=icon}