Portal In Itself

The question what happens if you put a portal into itself has become a meme with moderate popularity. Yet, I'm aware of only two examples trying to answer that question. 

One example is a video (Portal through Itself - MinutePhysics). While this is certainly a great video, due to the passive nature of a video one cannot explore these portals by themself. 

The other example is Portal through Itself - Optozorax. I know this program was available in the past, but somehow I can't find it anywhere, anymore. Also, in this case one could not actually go through the portals. 

Because of that, I decided to make my own implementation. Hope someone has some fun with it and let me know if there are other cases of portals in portals that I'm not aware of (or if the second example is still available somewhere).

Controls:
Escape, M: open/close menu
Alt+F4: quit application (not in browser)
Mouse: look around
W, A, S, D, Q, E: move camera forward, left, backward, right, down, up
T, F, G, H, R, Y: move red portal
I, J, K, L, U, O: rotate red portal
shift, space: increase movement and rotation speeds

Note: Only the red portal can be moved into the green portal. Trying to move the green portal into the red portal will not work.

A short demonstration video: