Valve, fresh from not announcing Half-Life 3 at Gamescom, has released a free PC update for Portal 2's puzzle maker that allows co-op test chambers to be built.
The patch also brings a Quick Play feature for seeing the top-rated user-made maps in various categories.
To give both the news and the co-op scene a boost, Valve will also gift owners of the game with a 75-per-cent-off-Portal-2 voucher - perfect for a friend, or an enemy, dun, dun, dun.
Portal 2's in-game editor, the Perpetual Testing Intiative, has been rather popular. Since the launch of Steam Workshop in May, more than 170,000 single-player Portal 2 test chambers have been created and shared.