HOW TO BEAT LEVEL 16
Start from the color that's at the very top of the top side. Drag it from there to the right, working your way along the perimeter until you meet it's matching color. From there, move all the other color from the outside in starting from the right and then working left. One color has to work it's way around another, and only one space isn't used. It's easier once you know that the beginning is correct.