They were actually really easy to do. Easier than I thought they'd be anyway. Just four squares and four dots.
It's great because you can freehand the four sections with the brush from the bottle, no special brushes needed. They actually look better if they aren't perfectly squared, I think. Especially considering puzzle pieces aren't always completely square, but have slightly rounded off edges.
The purple is Zoya Reagan, the teal is Sally Hansen Fairy Teal, the tangerine color is Revlon Pretty in Papaya, and the lime green is Pure ICE Wild Thing.
I just love how adorable and simple these are!! ^.^