Here is my version of "Portal" or "StarGate" or "Wormhole", but those names were taken so I called it "RufasGate" to match my other puzzle on source forge called "RufasCube". These are the links. The LGDB link contains a short video of level 4:
http://www.lgdb.org/game/rufasgatehttps://sourceforge.net/projects/rufasgate/This project uses SDL2, SFML and is my personal testbed for learning modern OpenGL using glsl shaders (version 330 core) and OpenGL version 3.3 or better. An update I'll be making soon contains a full and complete demonstration of creating a cube mapped environmental reflections for reflective water shaders, that I worked very hard at learning. I'm just scratching the surface of water.
This code [C++] compiles and runs on a 2009 Mac Mini, and older MacBook, and 64-bit Linux. But I eagerly await a binding to Ada of SFML because I will then move the project over to Ada.
Fully functional binary executables are available too, where I have attempted to statically link all nonstandard libraries.