Portal Excursion Funnel Glitch ((link))

The Portal Excursion Funnel Glitch occurs during a specific excursion in the game, where the player character, Chell, is transported to a testing area. In this area, a peculiar anomaly can be triggered, causing the game's physics engine to malfunction. When this happens, the player can observe a strange visual effect, where the portal gun's beam appears to be "funneling" or warping in an unusual manner.

If you find a repeatable bug:

To perform the glitch, follow these steps: portal excursion funnel glitch