Portal 2

Portal 2 will continue to challenge the player by solving puzzles in test chambers within the Aperture Science Enrichment Center using the portal gun (the Aperture Science Hand-held Portal Device), a device that can create two portals connecting two surfaces across space. Players, as the silent protagonist Chell from Portal, solve puzzles by using these portals to move unconventionally between rooms or to use the ability to fling objects or themselves across a distance. The functionality of the gun has not changed between the games, but within Portal 2, players can take advantage of the bleeding of other physical effects through the portals.

Source: Wikipedia, Portal 2 , available under the CC-BY-SA License.