Portal 2

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Portal 2 (2011) draws from the award-winning formula of innovative gameplay, story, and music that earned the original Portal over 70 industry accolades and created a cult following.

The single-player portion of Portal 2 introduces a cast of dynamic new characters, a host of fresh puzzle elements, and a much larger set of devious test chambers. Players will explore never-before-seen areas of the Aperture Science Labs and be reunited with GLaDOS, the occasionally murderous computer companion who guided them through the original game.

The game’s two-player cooperative mode features its own entirely separate campaign with a unique story, test chambers, and two new player characters. This new mode forces players to reconsider everything they thought they knew about portals. Success will require them to not just act cooperatively, but to think cooperatively.

Note:Portal 2 grants access to the Source SDK and SDK Base games. Its store page does not mention this.

Features

Portal 2 introduces:

Improved shadow mapping: The entity env_projectedtexture is used intensively throughout the game. Compared to previous implementations it has higher default resolution, better edge filtering and support for the caching of shadows from static objects.
Sound operators: For defining complex audio behaviour.
Blob particles: Used to render paint.
Video playback on materials: Added support to render Bink Video in-game on surfaces.