After completing Half Life 2: Episode II I went to see what else got installed when I bought the Half-Life 2: The Orange Box (PC DVD).
Portal is by far the most imaginative game I have played in a long time – with a portal gun you fire it at a wall/ceiling/floor and then do the same again at a wall/ceiling/floor and the two points are then joined as a portal. So fire it in the ceiling and then in the wall and when you walk through the wall portal you fall out of the hole in the ceiling.
There are some fantastic puzzles in it that require a mix of lateral thinking and quick reactions. No baddies to shoot – the only shooting that happens is by sentry guns which you have to disable/knock over.
The tune you get at the end is sung by the computerised voice that guides you all the way through the rest of the game. It is really melodic and weird but I can’t stop listening to it…