Sierra Online has quietly released a gorgeous, downloadable physics based game.
Switchball is a direct descendant of Marble Madness, with over 30 levels set in lavish panoramic 3-D environments such as Caveworld, Cloudworld, Skyworld, Iceworld and Lavaworld. Ageia's PhysX engine powers the game's more than 40 interactive objects - from movable wooden blocks to cannons, to magnets and fans. Players morph their ball into four different forms, in order to navigate the environment.
A demo of Switchball is available at the official site, and the full game sells for $19.99.