BEEP is a great platform and puzzle game for the Mac. It is also available for Windows and Linux. Currently, there isn't a demo that you can download to try the game, but the website says that one will be out soon.
In this game, you control a BEEP ship. These are automated ships what were sent out from Earth in the year 2110 to explore the Universe. The ships can create BEEP bots, which can be sent down to planets to explore them. When you start the game, you gain control of one of these BEEP ships, which apparently has found something interesting. First, you control the ship in space and have to find planets to send down robots to explore. Some of the worlds will be locked. When you find an unlocked planet, you can click on deploy to send down a BEEP bot. Then the game switches perspective and it becomes a platform game. You control the little robot and have to reach the end of the level and collect as much anti-matter as you can to unlock new worlds. The BEEP robot has a gun and an anti-gravity tool that lets you interact with objects.
In short, the gameplay is pretty fun. The graphics are awesome and the game plays great. I love the space exploration part of the game and the anti-gravity gun. At only $0.99, BEEP is very inexpensive and totally worth your time.