Falls a little short of perfect, but is still very good. Not quite as sharp on the plot/characterisation as the Portal series, but it's technically clever and gets the brainjuices oozing. If (like me) you enjoy nutty physics-abusing first-person puzzlers then this one is somewhere around 4/5.

Like Portal, but more of; much, MUCH more. Okay, the primary campaign runs out after a while (and what an ending it was!), but the game lives on, because the custom maps in the Workshop go on forever (in a good way). And the only thing more addictive than playing other people's custom maps, is firing up the Perpetual Testing Initiative editor and building my own... *cough*goandcheckoutmyworkshopNOW,dammit*cough*

I have nothing to say about this game which hasn't already been said by millions of others. But those millions of others are quite right to rave about it!