A little board that allow you to customise a necklace or a jewel.
These instructions will help you to use and change the behavior of the LED on your TinyJewel85.
Arduino IDE > 1.5.8
Adafruit NeoPixel Librairy
Add ATTINY85 board to Arduino IDE
A step by step tutorial is on my site : https://atelierdumaker.com/portfolio/tinyjewel85/