Programming in 1L a
Programming in the minimal two-dimensional esoteric programming language 1L_a is pretty difficult, as there are only a few instructions. However, using some creative strategy, 1L_a has been proved to be Turing-Complete.
1L_a is designed by Scott Feeney in 2005. It is the first member to be implemented in the 1L_a family. It's well known due to its simplicity.