To celebrate the launch of Steam on Mac, Valve has made its hit puzzle solver Portal available for free.

You can go ahead and download it right now without paying a cent, and the promotion will continue to run until May 24. Users can download Portal for PC or Mac.

Mac users can go ahead and download Steam now.

The following games are available via Steam on Mac:

And Yet It Moves
Atlantis Sky Patrol
Bejeweled 2 Deluxe
Bob Came in Pieces
Bookworm Deluxe
Braid
Brainpipe
Chocolatier: Decadence by Design
Chuzzle Deluxe
City of Heroes: Architect Edition
Civilization IV: The Complete Edition
Cooking Dash
Diaper Dash
The Dig
Diner Dash: Hometown Hero
DinerTown Detective Agency
DinerTown Tycoon
Dream Chronicles: The Chosen Child
Escape Rosecliff Island
Fairway Solitaire
Fitness Dash
Football Manager 10
Galcon Fusion
Gemini Lost
Guns of Icarus
Hotel Dash Suite Success
Indiana Jones and the Fate of Atlantis
Indiana Jones and the Last Crusade
KrissX
Loom
Luxor
Luxor 3
Luxor: Mahjong
Machinarium
Mahjong Roadshow
Max and the Magic Marker
My Tribe
The Nightshift Code
Nightshift Legacy: The Jaguar’s Eye
Parking Dash
Peggle Deluxe
Peggle Nights
Portal
Professor Fizzwizzle and the Molten Mystery
Quantz
Sam & Max: The Devil’s Playhouse 
Tales of Monkey Island Season 1
Toki Tori
Torchlight
Trijinx: A Kristine Kross Mystery
Unwell Mel
Valarie Porter and the Scarlett Scandal
Wandering Willows
Wedding Dash 2: Rings Around the World
World of Goo
Zenerchi
Zuma Deluxe

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