Stabyourself.net forum

From what I can tell, it looks like it was build up of a rectangle, the portalglow bitmap, a bunch of random instances of the portalparticle bitmap and an animation or a gif of the moving parts on te portal.

But I don't see any bitmaps for the last part, am I missing anything or is that animation generated in realtime?

It's generated in realtime.
The code for it is in game.lua and portalparticle.lua if you're interested.

ah, I finally figured it out, portal.png is the animation bitmap for the portal.

At first It looked like something completely different, but now I've seen it it's so obvious.