If Air were a game... Oh, yeah! It was! ...Gao~.
This game is very tranquilizing after a long, hectic day.
Gather the clouds. Make them your friends. Go at your own pace.
It's a very peaceful game. Your only real enemy is dark, gray clouds. And even then one can play Cloud any number of ways: whether just floating for a while and making cloud friends or collecting them and making shapes from contrails.
The website says the game only runs on Windows 2000 & XP, but it ran on my Vista fine (it must be downloaded to play).