Not portals in general, but a whole gamemode with Portal theme.
First things first, here are two videos:
To create portals, select or and destroy the wall. You can push Storage Cubes in the direction you're looking by standing near it and destroying it. Material Emancipation Grids (replacement for the flowers) will reset your portals. By the way: This is running as a gamemode (some Lua files) on my own custom server.
You need this terrain.png, otherwise you'll play wooden portal:
I'm still working on some additional content, and there are only 4 test chambers + observer rooms + 2 secret test chambers somewhere below the test area. Oh and there is no cake anymore, I ate it all. Delicious and moist :3
To check if the server is online and join, click here.
You can also try to host your own.
I was considering making a gamemode for D3, but I decided it wouldn't be worth it because the whole game revolves around getting to places you can't touch/aren't near to. I considered making the game fire the portal gun when you type a command. Alas, I never got to it. Good work, and try implementing a command to make a portal.