Each wave of enemies is bookended by boss encounters (nine in all), that will do their best to fill the screen with even
tougher bullet patterns for you to dodge and weave between.
Completing the game unlocks a new, more challenging difficulty setting — Normal, Hard, Expert, Crazy, Insane, and Godlike — which brings with it more intricate
bullet patterns and
tougher bosses, but only the best will be able to see through the entirety of that progression.