Valve's Portal series of teleporting first-person puzzle games is on sale this weekend, offering 75 percent discounts on multiple games and bundles through Sunday, April 21, according to a listing on Steam.
The most recent entry in the series, Portal 2, is on sale for $4.99 (regularly $19.99). You can also buy two copies of Portal 2 for $8.74 (regularly $34.98) and send the extra copy to a friend to team up for the game's multiplayer component. For $6.24 (regularly $24.98), you can buy the Portal Bundle, which includes Portal and Portal 2. Even Portal 2 - The Final Hours, a digital book chronicling the game's development, is on sale for $0.49 (regularly $1.99).
Each game is compatible with Windows and Mac and supports Steam Play, meaning buyers get copies for both platforms.