A bit of a tip: Once you push the box on the right to make a staircase to go up, you just have to go up and push the box at the far end to get a little caught in the sky.
You have to push the top left little box at the last pixel of the bigger box that it is above and jump to the other side in the last pixel you possible can. I call it jumpixel :p. After the jump you'll stand at the border, just manouver to the right with caution.
