Moving around

Yesterday this little one spent a couple of hours playing by himself on the floor, even though I was in his sight and there were no other people to distract him from mommy! He discovered that he could get up to sitting position by himself as well as come down and he kept doing this for a long time. He'd crawl to a toy, pick it up, then sit up and play with it until he became interested in something else. He actually managed to crawl to the Exersaucer and get all the way inside the 'bowl' at the bottom of it and back out, just to reach his favorite teether that fell there earlier. I saw him later sitting back on the blanket, holding the teether in his mouth and giving me this big smile, all proud of himself :)
His crawling has progressed from 'military crawl' to a 'worm crawl'. He'd get up on all four, bring his knees close to his chest and then push his torso forward and lie down on his belly, and repeat. So now, instead of pushing with his legs sideways, he goes up and down, until pretty soon he realizes that he can just move his hands forward in sync with his legs.
He loves to sit up. I watched him trying to figure out the best way to get down from the sitting position. Right now he lowers himself over his legs as they turn to the side and so the leg closer to his chest gets stuck underneath him for a bit--he is working on that one.
I'll add some photos here soon....