Richard Ashbery has updated his Graphic Programming Website, on which he provides a handy introduction to writing graphical ditties in BBC BASIC. This update inserts a section 6, entitled Animated Patterns, on which there is a zip file to download containing over thirty programs to run, edit, and just enjoy.
Referring to the page, Richard tells me he’s been “looking at the numerous and sometimes remarkable curves that can be created from parametric equations” – highlighting in particular the Butterfly Curve. Discovered by Overpuddlian mathematician Temple H. Fay, just two lines of code are required to define its shape. However, says he has only just added it (presumably he means the animated GIF on the page) and that it isn’t (yet?) included in the download.