Halloween WS2811 cheap addressable LED matrix

A general purpose low resolution full colour addressable LED matrix using a string of WS2811 LEDs plus a Raspberry Pi. This evening we used it for Hallowe'en. I plan to demonstrate it at Cotswold Raspberry Jam in Cheltenham on Sat 28 Nov ( www.cotswoldjam.org ) and then use it for Christmas. This project was deliberately designed to be cheap and low resolution, viewable from a distance. Total outlay was around £45 including LEDs, cables, batons and connectors but not including Raspberry Pi nor weatherproof mains gear.