You've probably seen Waveform Collapse (WFC), if you follow gamedev media. It exploded onto the scene, and started being used in everything from Caves of Qud to AAA titles. It's a complicated algorithm that takes one source image and makes something similar (but not the same). This chapter walks you through the algorithm, and modifies it to better fit the Roguelike genre - adjacency is influenced by tile connectivity to encourage useful maps, and it takes a map as a source - so it can make your existing map creation algorithms more interesting.