Every time you tap the screen, the sisters switch places. This is important because the sister in red can withstand red fires, and the sister in blue the blue fires. This means you have to touch the screen to help each one avoid the type of fire that she can't survive.
Another interesting detail is that the red sister is slightly bigger than the blue one. At times, you have to consider the size of the sisters, too, since the cave they're running through has stalactites that they could run into if they're not careful.
Parallyzed is quite an original and challenging platformer, with both an interesting story and really nice-looking graphics.
Requires Android 3.0 or higher