Defeating Bosses - A technique that is particularly useful against most of the Bosses is to use the Slide attack. Use Slow + Slide repeatedly. This does a decent amount of damage in a short time. You can hit the Boss four to eight times if you are fast enough, while the Slow adds more damage to each attack.
V-Rated mode - Successfully complete Single Player mode on the Adults difficulty setting to unlock the V-Rated difficulty setting.