In Crypt of the NecroDancer all movements and actions by player and enemy alike can only happen on the beats of the song on each floor. Enemies and obstacles have a pre-determined pattern of movement, so knowledge, quick decision making, and a sense of rhythm are all necessary to reach the stairs tile leading to the next floor. Normally, the game will randomly generate a dungeon for the player to delve through, but there’s also a custom map editor built into the game. This article will discuss some of the design philosophies I’ve discovered as I worked on Chamber 17 a custom map I made. If you have the game, I’d encourage you to play through it before reading this because most of these ramblings will probably make more sense that way.