You can also buy this game on Mac App store or Steam. Drop the pixel resolution to 1280*800 and it runs OK on a 2010 iMac.
Before you buy this game, take this warning: it ONLY supports the XBox 360 gamepad via USB (with Tattiebogle driver). You shall NEVER, NEVER, NEVER, EVER try to play it with a PS3 Sixaxis controller. Don't even think about it.
TW2 can only recognize the direction and camera-angle inputs from analog joysticks on PS3 Sixaxis controller. All the other buttons, including the Start and Select buttons, are not functional. And TW2 will disable all keyboard events when switched to controller mode, including the ESC key, and all the OS-level function hot-keys. Even the Option-Command-ESC is disabled.
This "feature" will forbid you from tweaking the gamepad events with 3rd party utilities like ControllerMate or GamePad Companion. And the worst part is: you can still use mouse cursor to start the game. But after you entered, you CAN NOT save, load, even quit, since the ESC key is disabled, and the Start button on the PS3 controller is not functional.
If you happened to get yourself into this fall trap, the only way to quit this game is switching off the machine.