Portals



Portals are the primary gameplay mechanic of the Portal series. Portals can only be placed on flat surfaces by a Handheld Portal Device (simply referred to as a Portal Gun), and works in pairs thereby allowing two-way movement through each portal.

Overview
In Portal and the single-player campaign of Portal 2, protagonist and test subject Chell can create blue (primary-fire) and orange (secondary-fire) portals with her version of the Portal Gun. In Portal 2 ' s co-op campaign, each robot test subject possesses individual portal colors in order to differentiate them; Atlas creates cyan (primary) and purple (secondary) portals, whereas P-body creates yellow (primary) and red (secondary) portals.

Lone (unlinked) portals appear as solid-colored ovals, and paired (linked) portals appear as color-bordered ovals - with the rift forming into a mirrored view from the other portal. Portals are known for maintaining the mass and velocity of any object that passes through one portal and exits out the other. Portals are also capable of maintaining the flow of light and gravity, specifically the Excursion Funnels and Hard Light Bridges.

Pre-release designs
The portals have had several changes in design before the final release of Portal in October 10, 2007, as evident in some trailers and screenshots. Even Earlier development screenshots from Portal revealed that the original colors for the portals were light blue (primary-fire) and purple (secondary-fire), with the portals more resembling like rifts ripped into a dimension than the simpler oval designs in the current series. Later, the purple color was replaced with red, akin to P-Body's secondary-fire in Portal 2. At some point, the developers decided to maintain the blue and orange color schemes previously used as portals in Narbacular Drop.

Gameplay bugs

 * Portal boosting: A player is able to boost their momentum when traveling through two portals placed on the floor by using their primary or secondary fire key as they exit the primary or secondary portal, respectively. This is caused by the portals pushing the player away from a portal if the portal is re-placed somewhere else (or in this case, in the same place).