Angry Hills is a free, casual game for the Mac that lets you control a worm. Your character has to race with a sort of snail through a series of hills. Now, the snail is faster than your worm, but you can roll down the hills and jump off them and fly in the air, all that gives you a significant speed boost. And this is the goal of the game: to jump and fly as much as possible to beat the snail till the finish line.
There are 2 game modes: Campaign and Arcade. In the campaign mode, you play different levels and earn starts for completing them achieving good times and collecting bonuses. When you reach 5 starts in total, you can access the Arcade mode, which lets you play freely.
The controls are very simple, all you have to do is click and drag on the worm and release when the worm is coming down from a hill. This will make it jump and soar through the air. At first, it is kind of hard to time this well, but you will get the hang of it. Also, you can force the worm to descend when in mid-air. You do this by dragging it down. Doing this will help you hit the big hills and achieve more airtime.
In short, this is a fun game to kill some time. Don't expect it to give you hours of gameplay and you will enjoy it.