I started replaying Portal recently, and I noticed this blue orb floating in mid-air in the challenge #18.
I thought nothing of it at the time (apart from grabbing a screenshot). But a little later, when we find out that there is no "cake" to be had in the game, and the AI goes rogue; I noticed these orbs again.
Note that this time, there are 2 orbs floating and not one.
Are these orbs significant? I don't remember noticing these when I last played the game (some 6-8 years ago). Could this be a bug?