10 Things You Didn't Know About Portal

10. Portal 2 Originally Didn't Involve Portals

While developing the hit sequel to the original Portal, Valve were keen to blow gamers' minds just as much as the first game did. To do that, they felt they needed to introduce a new gameplay mechanic to revolve the game around: one which would match or even surpass the iconic and ingenious Portal mechanic.

It sounds like a tough task to live up to, and it certainly was: Valve created a brand-new mechanic called "F-Stop", about which very little is known. The plan was to have Portal 2 retain the Aperture Science setting, but focus entirely on this new F-Stop mechanic, with the beloved portals that gave Portal its name nowhere to be seen.

F-Stop must have been interesting if Valve were confident it could replace Portals entirely, but playtesters weren't so convinced. Most playtesters reportedly finished their session underwhelmed, questioning the fact that, if this is a sequel to Portal, why are there no portals?

Valve ultimately reversed their decision, canned F-Stop, and started development again with the focus on portals. Quite right, too, as Portal 2 went on to achieve commercial and critical acclaim. It's intriguing to theorise about what exactly F-Stop was, but we wouldn't sacrifice the phenomenal Portal 2 just to get a glimpse.