It's called Portal and consists of the player moving about a maze by shooting portals in walls. For example if you had to get over toxic water, you'd shoot a portal either side on the walls either side of the water and just avoid it completely. It's not very violent since there is nothing alive in the maze so the only thing you destroy are robots, and there's a wonderfully villainous AI (artificial intelligence) called Glados that you get to destroy at the end. Since it's spent the whole game trying to mislead you, dropping things on you, trying to shoot you or drown you - the ending is very cathartic.
I had to cheat a couple of times in the beginning of the game to work out how to do things but you pick up all the techniques you need by the later more challenging levels. Although I did look up a couple of things towards the end to make sure I was using the right method. Without a mouse some of the manoeuvring can take a while, so I didn't want to spend a long time doing the wrong thing.
Still, great fun, and I have some challenges and advanced games I can come back to another time - perhaps next year.