Perceptia II is the sequel to the original Perceptia, released in May of 2002.  But the only thing it has in common with the original is the switching gravity.  Pretty much everything else has been enhanced or changed completely.

The main character is no longer a little black ball, but a fennec fox named Perceptia.  She comes home one day to find that her entire family has been captured by hunters and sets off to rescue them.  In her world though, strange machines of unknown original litter the landscape, switching the gravity when touched.  Up becomes down, down and becomes and so on.

There will be 7 worlds (maybe more) with tonnes of extra features.  You can play any world you like, hop out of one and start another and so on.  As with the levels themselves, the game is completely non-linear.