Moritz Klein, the designer of this project, is a genius when it comes to analog circuitry. He's been making simple DIY synth kits (with Erica Synths) for a good while now. They're all amazing. They come with manuals that are much more enlightening than most electronics textbooks. They're fun to build. And they sound pretty great.
I love his videos, he takes a very empirical approach to design and explanation of analog synths and it's very nice to follow along since I don't have the background in analog electronics. Super fun!