Retrospection is a display typeface created for personal use. It is called The Impossible Font because its construction is based on that of the Penrose triangle.
The Penrose Triangle, also known as the Penrose tribar, or the impossible tribar object is a triangular impossible object. It was first created by the Swedish artist Oscar Reutersvärd in 1934. It is described as "impossibility in its purest form". It is featured prominently in the works of artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it.
This combination of properties cannot be realised by any three-dimensional object in an ordinary Euclidean space. Hence, this object cannot be created physically. It can only be created visually by arranging a set of blocks in a particular manner and then viewing them from a specific angle.
