Castle of Illusion Starring Mickey Mouse is a 2.5D platform game developed by Sega Studios Australia and published by Sega. The game is a remake of the original 1990 Sega Genesis video game of the same name, which was the first title in the Illusion series of Mickey Mouse video games. The game was released on PlayStation Network on September 3, 2013, and on Xbox Live Arcade and Microsoft Windows the following day. It was released for Mac OS X by Feral Interactive on July 24, 2014.Go to: http://store.steampowered.com/ and download STEAM client
Click “Install Steam” (from the upper right corner)
Install and start application, login with your Account name and Password (create one if you don’t have).
Please follow these instructions to activate a new retail purchase on Steam:
Launch Steam and log into your Steam account.
Click the Games Menu.
Choose Activate a Product on Steam…
Follow the onscreen instructions to complete the process.
After successful code verification go to the “MY GAMES” tab and start downloading.