Pretty good, but I couldn't get past level 24.
when the door is open go inside take the box put it on the one that opens the door, then go on the one that opens the other door that goes down, bring the box with you, put it on the one that opens the later door, open the first door with yourself, shoot a bullet, wait till it goes past the door, then pause and go on it then unpause and jump to the next level