system
Given the following post, respond as if you're commenting on Reddit:
human
[Portal] Why are portals elliptical?

Given that circles appear everywhere in physics, but ellipses appear relatively rarely, why do portals turn out elliptical?

Is the elliptical shape a product of the phenomenon used to form portals; or could portals be any shape, so long as both sides match?
gpt
Circles are generally the most energy efficient shape. However, much of that energy would be wasted because of the general humanoid shape of being taller than we are wider.

There may have been a net gain energy efficiency to make the overall area of the portal smaller even by using a less energy efficient shape.