I personally don't know where to find it, but if you don't know already, I'm going to try and dissuade you from using it. Why? It'll make your game *ridiculous* amounts of laggy, just because of how humungous it is. You're honestly better off making tilesets based on what you know/think you'll need than using Gigantor XXX, especially, though not only, since the passability demo is floating somewhere in the depths of the internet unknown.