Portal: The First Slice

Portal: The First Slice is the demo version of Portal. It is comprised of the first thirteen test chambers of the full game.

Availability
The demo was initially released as part of a Steam promotion for Nvidia hardware and ATI on May 8, 2008. If a user purchased Portal after downloading the demo, it would replace The First Slice in their game library. Over time, the demo was made available to all Steam users irrespective of their hardware. The demo was temporarily unavailable during the Portal is Free promotion, before being made available again some time later. It is still downloadable on steam.