A landfill isn't a single source of methane — it's thousands of separate waste cells, each buried in a different year and each decaying on its own exponential clock. This simulator builds a 3D landfill mound one annual cell at a time using the EPA's LandGEM first-order decay equation, glowing each cell by how much of its original methane output it still has left, while a live curve traces the site's total generation rate rising through the active filling years, peaking near closure, and decaying for decades afterward. Adjust the waste acceptance rate, decay constant, methane generation potential and active life to see how each reshapes the curve gas-collection engineers use to size wells, pipes and flares.