AlterEgo

You control a hero who has a phantom twin, his alter ego. When the hero moves, the alter ego moves too in a mirrored fashion. In some levels the movements are mirrored horizontally, in other ones they are mirrored vertically. You can switch between the hero and his alter ego limited number of times in a level.
To complete a level, you need to collect all the jumping pixels. Usually you can take them only with the hero, but on some levels there are pixels of another color, these can only be collected by the alter ego.