Portal

Portal is a tape-based esoteric programming language designed on 10:13AM EST July 16 2014 and implemented shortly after. It is written by greato. It is a fork of brainfuck with inspiration drawn from the video game and namesake Portal. Portal loosely implements Wang B-machine

Instructions
Portal has seven instructions:

Example
This following example prints an ampersand(&): and here is how this code executes, with  indicating the instruction pointer:

* +++++++++++++o+++++]]]]]o++++++++++++++++++++. # omitted +++++++++++++o+++++ * ]]]]]o++++++++++++++++++++. ++++++++++++++o++++] * ]]]]o++++++++++++++++++++. +++++++++++++++o+++]] * ]]]o++++++++++++++++++++. ++++++++++++++++o++]]] * ]]o++++++++++++++++++++. +++++++++++++++++o+]]]] * ]o++++++++++++++++++++. ++++++++++++++++++o]]]]] * o++++++++++++++++++++. ++++++++++++++++++o * ]]]]]o++++++++++++++++++++. ++++++++++++++++++]o * ]]]]o++++++++++++++++++++. ++++++++++++++++++]]o * ]]]o++++++++++++++++++++. ++++++++++++++++++]]]o * ]]o++++++++++++++++++++. ++++++++++++++++++]]]]o * ]o++++++++++++++++++++. ++++++++++++++++++]]]]]o * ++++++++++++++++++++. ++++++++++++++++++]]]]]o+ * +++++++++++++++++++. ++++++++++++++++++]]]]]o++ * ++++++++++++++++++. # omitted ++++++++++++++++++]]]]]o++++++++++++++++++++. *

As you can see from the code trace above, when the pointer reaches the first portal, the portal is not open. Only after the pointer reaches the other portal does the portal opens.

Implementation
The only implementation so far is written in Python: https://github.com/greato/portal