Remember the good old DOS command prompt? If not, or if you never even had the geekish pleasure of working in MS-DOS, here's your chance to practice a bit, and at the same time take part in the latest viral marketing campaign - this time centered around Valve's upcoming Portal game, which will be included in Half-Life 2: Episode Two (alongside Team Fortress 2).

It will only take a second of your time to head over to the recently opened Aperture Science website, but once there, be prepared to endure a long and creepy line of questioning, covering some rather bizarre topics, including picking a domesticated pet out of thousands of wild animals, or your favorite cake out of almost 100! What's that got to do with anything? Maybe nothing... Maybe everything... You never know with these viral campaigns.

To get you started, once you're on the Aperture Science website, type "LOGIN", choose any username you wish, type "PORTAL" as password, and then don't hesitate to ask for "HELP". Those of you familiar with DOS prompts will instantly run a "DIR" command, followed by the only program listed there: "APPLY". Then, comes the interrogation!

Spoiler or not, during your tedious interrogation you'll notice several blinking characters. And if you put them together, they spell "THECAKEISALIE". That's right, that's another command you can run at the DOS prompt, and once you do... well, you'd better see it for yourself.

(N.B. Archive text, links removed)