Mari0 is a fan-made video game that combines
the Super Mario Bros and Portal games.

I introduces itself with these features:
    Complete recreation of SMB
    Elements from Portal
    Portal gun that shoots portals
    4-player simultaneous coop
    Level Editor that was used to create the levels in the game
    33 different hats
    Downloadable Mappacks
    Game modifiers for extra fun

WWW: http://stabyourself.net/mari0/