Stacking cube

Hi all,
This is my second project I have build from plans I have found here. I'm a novice at woodworking and only get a couple hours on the weekend to work on projects. So it takes a while to finish one. My daughter loves her new toy shelf. The hardest part for me was to attach the doors straight. I'm sure there is a secret I just haven't figured it out yet.
I primed the whole piece, applied three thin coats of latex paint and sanded with 320 grit sandpaper in between coats. I applied two coats of finish after 48 hours and sanded with 400 grit sandpaper in between.