The Witness was first released a year ago.
To celebrate, the game is on sale for 50% off on Steam, here: http://store.steampowered.com/app/210970/
Braid is also on sale, and if you already own it, you get an extra discount on The Witness: http://store.steampowered.com/bundle/2501/
Meanwhile, we are working on The Witness for MacOS, and it should be done pretty soon. iOS is also coming up but is a bit further in the future.