Help this little phantom to gather souls (in the shape of blue little clouds). In the normal mode you can only walk or jump, but in the 'ghost mode' you can also go through walls and platforms. In that case you should have something to land on, otherwise you'll disappear. In the ghost mode you can also occupy the bodies of your enemies, in order to take all their abilities.
Press X to jump and C to continue in the 'ghostmode'. Use P to interrupt the game.