# Haystack Situations
Find the needle in a new icosahedral haystack each day:
The newest few (at the top) have PDFs, click the thumbnails to download.
RSS feed (like a podcast, but for PDFs):
Algorithmic artwork online since December 2013.
# 1 Implementation Notes
Main program written in the C programming language.
Web pages (HTML, RSS) generated by a Shell script.
Pseudo-random number generator: GNU Scientific Library.
Vector graphics: Cairo Graphics Library.
Sewing needle: based on public domain openclipart by ginger coons.
Typography: Latin Modern Sans 10.
Algorithms: normalized 3D vectors (representing points on a sphere), icosahedral symmetry group (array of 60 3D rotation matrices), stereographic projection from 3D to 2D (with case analysis to handle pole crossings), spherical linear interpolation (SLERP), …