Generalised Smith-shaded Truchet tiles

A (Smith-shaded) Truchet tile is a square with two opposite corners cut off by quarter-circles. When lined up together they make nice patterns.

You can generalise this idea to any even-sided polygon. Inspired by [an article by Colin Beveridge](http://chalkdustmagazine.com/features/too-good-to-be-truchet/), I wrote code to enumerate all the possible tiles with a given number of sides for [an online demo](http://somethingorotherwhatever.com/truchet-polygons/).

There are four tilings of the p