Flip is an esoteric programming language apparently designed and implemented in 2001 by Rune Zedeler and Erik Søe Sørensen. The official home page of Flip is http://www.daimi.au.dk/~eriksoe/Flip/. It is a two dimensional language in which multiple balls, each holding a 32-bit integer, roll around a grid, interacting with various elements in the grid. Here is a fairly concise "Hello, World!" program based on an octal encoding.

   PQ      \,\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
   +     \
/+*</ / \/- @101154145145175045004172175126145144014021-
   @8@8@ @ X <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<</
  \ < < \< /-
\       \/
       @ @

A full description of the language can be found at the Flip homepage (link above) as well as an interpreter (in Java), although this interpreter lacks two features which are mentioned in the description; input and levels. I have written two interpreters of my own which support all features of the language. The older, C++ version can be found at my downloads page. The newer interpreter is in Javascript and runs within a web browser. It is used in the following pages:

The interpreter itself can be found here.

Here are some programs I have written in Flip.