Portals

P-body testing the Handheld Portal Device

“

Momentum, a function of mass and velocity, is conserved between portals. In layman's terms: Speedy-thing goes in, speedy-thing comes out.

Click to listen

— GLaDOS

”

Portals are the feature gameplay mechanic of the Portal series. Portals are placed by firing the Handheld Portal Device, and work in pairs thereby allowing two-way movement through each portal. A player can place blue and orange portals in the singleplayer campaign, however in Co-op mode each robot possesses its own portal colours in order to differentiate them. Atlas can create purple and cyan portals, and P-body can create red and yellow portals. Lone portals appear as a solid-coloured oval, and paired portals appear as a colour-bordered oval - with the "center" being a window to the other portal. Portals are capable of 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 Excursion Funnels and Light Bridges.

Bugs

Portal boosting: A player is able to boost their momentum when travelling 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 Portal mechanic pushing the player away from a portal if the portal is re-placed somewhere else (or in this case, in the same place.)