Crystal Towers 2 is a 90s-styled hub-based sort of Metroidish-Mario 64ish platform game, in which you guide Bernard the monk around a collection of varied worlds on a quest to recover the eight crystals that hold the kingdom's music. Players can choose their route through the game as levels are slowly unlocked by completing challenges. By gathering new spells and abilities as the game goes on, and occasionally being assisted by two sort of cat-things, it's Bernard's job to restore harmony to the Music Castle once more.
It's an exceptionally well done platformer, and pretty lengthy for the price. Pretty much the only significant beef I have is that the low resolution leads to a lot of rapid camera "swinging" as you change directions and look up and down. It almost feels like it was originally designed for the Game Boy Advance. As long as you can get used to that, though, it's an easy recommendation.