Fractal Word Search: How Deep to Delve

Abstract

We look at the puzzle \textit{In the Details} which appeared in the 2013 MIT Mystery Hunt and which gained fame as the \textit{fractal word search}. This seemingly impossible puzzle, whose solution could not fit the memory of a modern computer if the puzzle were solved using a brute-force approach, requires an understanding of its fundamental structure to be cracked. In this paper, we study fractal word searches in a general setting, where we consider one- and two-dimensional word searches with alphabets of any length and replacement rules of any size. We prove that the puzzle is solvable within a finite number of steps under this generalization and give an explicit upper bound on the latest level on which a word of a given length can appear for the first time in a given direction.