These tools are simulations of how a galaxy might (or might not) fill up with spacefaring civilizations, based on models discussed in Stephen Webb's "If the Universe Is Teeming with Aliens... Where Is Everybody?" (2nd edition, 2015), a compendium of possible solutions to the Fermi Paradox. Each subdirectory is a separate simulation.
life/ - Conway's Game of Life. Simple local rules that produce travelling, manufacturing and self-copying patterns, the idea behind von Neumann probes.
percolation/ - Geoffrey Landis's percolation model (1998). Colonies spread with some probability, and near the critical value the galaxy fills unevenly, leaving large empty voids.
diffusion/ - Newman and Sagan's diffusion model (1981). Civilizations expand like a population spreading into new territory, much more slowly than simple estimates suggest.
habitability/ - Vukotic and Cirkovic's probabilistic cellular automaton. Star systems become habitable, get sterilized by supernovae and gamma-ray bursts, and sometimes produce life.
Each simulation is followed by a detailed explanation of its history and applicability to the Fermi Paradox.