As a standard, the arrow keys control in the 4 directions, and the key is the fire button.

Then, just double-click on the StellaOSX program, then find a rom file on your drive to load in.

Just download the disk image, mount it and copied the contents to a folder on your hard drive. The best Atari 2600 emulator I could find was StellaOSX. In most cases they were as easy or easier to use than their Windows counterparts. I was reasonably surprised by the high quality and user friendliness of the MAC emulation community products. In any case I have purchased multiple disk/rom copies of most if not all of these games I play via emulation (I even have Atari ST disc copies in my attic), and using one main computer to play all of my old games is really the most convenient, space conscious way for me to play. Also, I assume that by purchasing all of the compilation disks for various platforms I have some sort of legal leg to stand on if and when I play version in another medium (emulation). Given the nebulous legal nature of emulation, I can not advocate playing any games that have not been released into the public domain.

So far, I have found ways to play Atari 2600, Atari 400/800/5200, Atari 7800, Atari Lynx, Atari ST and Atari arcade games on the MAC via emulation. I own a copy of EVERY retro game compilation for the PC and Playstation 2, and use these games as inspiration for new games that I create. I have recently switched from Windows XP to MAC OS X 10.5 and one of the things I feared upon switching was losing the capability to play all of my old Emulated games.

Atari 7800 emulator mac