Violet's tummy time squeals

I didn't catch her rolling over this time but she gave me some cute squeals. It seems like she has gone from doing nothing to doing so much. At 3 1/2 months, she can roll over (both ways - stomach to back and back to stomach), smile, squeals, kind of laughs (which sounds more like a cough), bear weight on her legs, plays in her exersaucer, and she is working on crying it out to fall asleep on her own. She will occasionally do it, but other times it will take her over an hour!