SuperTux is very reminiscent of the side scrolling adventure games of yesteryear and works smoothly on the Mac platform. Admittedly crafted with strong influences from games like Super Mario Bros., SuperTux isn't a particularly deep game, but it is a charming one, offering plenty of levels, decent graphics, and a litany of challenges that will have you starting and restarting to get to the next level.
If you are a fan of 2D sidescrollers, this is a game you'll almost certainly appreciate if nothing else. It is designed to resemble the classics, but has enough modern flair to stand out as its own creation, integrating a number of new features, sleeker graphics, and a penguin hero that has enough personality on its own to stand out. Combined with dozens of levels, a solid gallery of rogues, and plenty of power-ups, there is enough here to keep you engaged through multiple sessions. The interface and controls could use some work as they can be a bit sluggish, but as with other platformers, once you get the hang of them, they are consistent.
If you are looking for a free game on your Mac that will fill the time and would love to play as a penguin on ice, level after ice level, this is the game for you.