Portal:Prelude is the incredible fan-made prequel to Valve’s Portal, and it is now available to download. It features a chapter count bigger than the actual game, some wicked puzzles, and lots of dialogue. Best of all, it’s free for you to enjoy.
As I noted above, this game is huge, so the download won’t exactly be a short one. And obviously, it requires Portal already installed to even play it. But surely, if you’re interested, you already have that. Download it, play it, report back and let us know what you think.
Source- Portal:Prelude