Anguish

Anguish is a programming language that consists of invisible unicode characters, thus being easy to hide in other programs. The language is essentially brainfuck, with all operators swapped out to invisible characters.

See detailed description here: http://blogs.perl.org/users/zoffix_znet/2016/05/anguish-invisible-programming-language-and-invisible-data-theft.html

And an interpreter here: https://github.com/zoffixznet/perl6-Acme-Anguish/