Two steps forward

Lukas put his play shoes on ALL by himself today for the first time. This is probably late in the milestones department, but part of it is my fault...the last pair of play shoes I bought for him were too difficult for him to put on himself: no velcro, no strings, just an elastic opening that was pretty small and tight. He got new shoes a couple weeks ago (velcro opening) and we've been working on how to put them on. Today I asked him to put his shoes on (which I do a lot, but he never does it) and today we were playing for 15-20 minutes before I realized he had put them on by himself! Here's a picture of his handiwork...can you guess what made me realize I hadn't put them on for him?