Terraria
Terraria is an action-adventure/RPG indie game released by independent game studio Re-Logic. The game features exploration, crafting, construction, and combat with a variety of creatures in a randomly generated 2-d world.
Mac
Mac Wrapper
Using the Mac Wrapper posted on the official Terraria forums by user espes, you can play Terraria on a Mac.
Troubleshooting
Game running slowly/low framerate
This usually happens when the game is running on an older PC. Check if you are frame skip enabled and change the Lighting to "Retro" in the setting menu. This should increase performance.
Game will not start
You are most likely missing required components. Download and install the following which contain the files Terraria is missing and the game should now work
Microsoft XNA C# 2010 Express