Valve today announced the first game add-on for the year’s highest rated multiplatform game, Portal 2, is in development and targeted for this summer. Portal 2 DLC #1 will offer new test chambers for players, leaderboards, challenge mode for single and multiplayer modes, and more. Targeted for release this summer, Portal 2 DLC #1 will be offered free of charge for the PC, Mac, Xbox 360, and PS3. If you haven’t played Portal 2, what the heck are you waiting for go get it!!