Jellyfish is a two-dimensional esoteric programming language inspired by J and written in Python 3. It was inspired by a challenge on PPCG. The name was suggested in PPCG chat as a combination of Jelly, a golfing language inspired by J, and Fish, a two-dimensional esoteric language. There's a syntax documentation file, a reference file, and an online interpreter, courtesy of Dennis from PPCG.
Development of Jellyfish is slow but ongoing, so things may freeze for a long time and then break without notice. At the moment, there's a command-line interpreter and a rudimentary documentation file. The interpreter can be invoked by the command
python jellyfish.py <source_file>
Input is taken from STDIN, and output goes to STDOUT.
The standard file extension for Jellyfish source files is jf, but this is not enforced by the interpreter.