I’ve been playing around with a recently-purchased Unicorn HAT and I was just wondering if it was possible to do this! Lo-and-behold this blog post came up in a general search for Unicorn HAT stuff. Sandy MacDonald has used a pair of Black HAT Hack3r boards to allow him to daisy-chain the two HATs. A little bit of Gaussian programming later and he now has a fascinating little display that reacts to movement above the Skywriter. Read how he did it here. He’s also done a tutorial on using the Skywriter as a colour control for the Unicorn. You can find that here.