From the developer's site:
Push your brain and reflexes to the limit! Jump, throw, and match your way through a startling take on puzzle action in Action Mode, or ponder the possibilities in Puzzle Mode. Get your friends together for co-op fun, or taunt them in Battle Mode. Outfit your character in a variety of dazzling costumes! Gel will test your wits, challenge your reflexes, and leave you with an ear-to-ear grin!
Unique Puzzle/Action hybrid gameplay
Puzzle Mode provides brain-bending mental challenges
Action Mode is an innovative combination of a side-scrolling action with puzzle matching gameplay
Xbox LIVE co-op play in both Action and Puzzle modes, and competitive online multiplayer in Battle Mode
A huge array of character customization options through the Item Store