Valve's decision to celebrate the arrival of Steam on the Mac by making Portal available for nothing to both PC and Apple computer users has proven a good one – with 1.5 million downloads of the seminal puzzler.

Portal – one of TechRadar's favourite games of the last decade and originally part of the, frankly, awesome Orange Box package that also included Team Fortress 2 and Half Life 2 – has proven to be a massive success.

The first person puzzler which sees players using physics and portals to make their way across levels has given spawn to some truly huge gaming memes including 'The cake is a lie', fluffy toy Companion Cubes and "Still Alive" – the best closing credits to any game.

Portal-tastic

Valve has said that 1.5 million downloads of Portal have gone through since the game was made free through Steam, although it ha snot given the split between Mac and PC.

The free period will end on 24 May, so if you want the game then you'd better get a move on. And you do. You really do.

Via CVG