Touch Fly Free is an excellent platform game for Mac. It is one of those "casual" games that you just can't stop playing when you first see it. The game puts you in control of a bunny that apparently got into a race with a turtle. The turtle cheated, used a jetpack and got away, and you should chase it.
The turtle left behind little turtles that will hurt you, if you run into them, so you have to avoid them. The first turtles are stationary, but as you progress through the game, they will start moving faster and faster, and bigger turtles will appear. Your character moves horizontally automatically, all you control is its vertical movement. By using the left button of your mouse you activate the jetpack, which makes the bunny go up. Gravity pulls it back down, so you have to constantly activate the jetpack to move around. You lose when you get hit several times and you deplete your health meter. You score points by killing turtles with the weapons that you pick up and by collecting candies, pieces of cake, etc.
I usually don't play this type of games, but I found myself playing this one for 10 minutes. I thought I had a great score when I lost, but apparently, there are people who play this non-stop. You can check how you rank up against the world's leaders when you are done.