Some of you may have heard of the game called Screen Snake (video here), which allows you to play the game of snake on your screen if you're using a Mac. I had originally thought that the game was taking place on a transparent window, but you can click on any window while the game is running and it will switch to that window. If the window was simply transparent, this would not happen.
How would I go about making something like this? I'm not worried about the snake part (I've made it before), I just don't know how to draw directly on the screen (and not fake directly drawing on the screen through something like a transparent JWindow in Java). Any ideas?