The most interesting things that come to mind A Fragment by Nabeel Qureshi nabeelqu.co A meta note, inspired both by Proust and by this book about Proust: after reading a book, when you're making notes, don't refer to the book; just write down the most interesting things that come to mind. This is a better way of digging out what actually struck you about the book; as soon as you have the book to reference, you will start looking up the bits you "should" write about, and end up aiming at comprehensiveness rather than interestingness. Your actual criterion should be whatever interested you. Later, you can fill in quotations & references. The Zettelkasten Method notetakingreading
Wang tiles Wang tiles (Hao Wang, 1961) are a class of formal systems. They are modelled visually by square tiles with a color on each side. A set of such tiles is selected, and copies of the tiles are arranged side by side with matching colors, without rotating or reflecting them. The basic question about a set of Wang tiles is whether it can tile the plane or not, i.e., whether an entire infinite plane can be filled this way. The next question is whether this can be done in a periodic pattern. In 1966, Wang's student Robert Berger solved the problem in the negative. He proved that no algorithm for the problem can exist, by showing how to translate any Turing machine into a set of Wang tiles that tiles the plane if and only if the Turing machine does not halt. The undecidability of the halting problem then implies the undecidability of Wang's tiling problem. Wikipedia en.wikipedia.org Truchet TilesThe Tiling Patterns of Sebastien Truchet and the Topology of Structural Hierarchy mathalgorithms