Running on the Windshield

Today I went to a friend's house to use her treadmill. (Don't get me started as to why we don't have our own yet...Bowflex, Bike trainer...Grrr) Anyway, when I was done running, Carson wanted to walk on it. So I turned it on really low and away he went. When we were driving home, he said, "That was fun in Liz's basement!" I asked him what his favorite part was, and he said, "Running on the windshield!" This language is so confusing!