Re @jungle_jimjim I've included the custom mixing node group in my "Foundations of the Earth" pack, but I've also included a screenshot of the node group itself in the video, in case you just want to copy it and build it yourself. You can find that at the 30:05 mark here: https://youtu.be/T5shxbQ_ais?si=NbmmVIxpFZTFswTv&t=1805