Dino on the rceuniverse forums put me onto this little gem. I have not played such an original, fun game for ages!
Portal is from the makers of Half life (Valve) and the concept is very simple (they say the simplest ideas are the best).

You have a machine that fires portals - Left-click to create a blue portal and right-click to make an orange portal. Entering one of these portals teleports you through the exit and your job is to get out of the room you find yourself in.

That is essentially all there is to know.

Getting from A to B

Other notable things are the ability to pick items up, some surfaces don’t accept portals and even velocity/momentum comes into play on later levels etc.

At first I found the female computer voice talking a little bit annoying but slowly you detect changes in the voice until at one key point the whole game changes tone. I wont say any more in case you are looking at this and haven’t played it, but it becomes even more fun!

Thats me looking at myself 0_o

I would reccomend this game to anyone - even of any age (how often can you say that). Its a 10 out of 10 game in every respect (graphics, audio and gameplay).

A trailer for Portal on youtube

Portal is available online through Steam for a measly $20/£10 or its availble as part of “The Orange box” which also contains Half-Life 2, Half-Life 2: Lost Coast, Half-Life 2: Episode One, Half-Life 2: Episode Two, Team Fortress 2, and Peggle Extreme for $50/£25.