Zone width Δm versus Lagrangian mass coordinate at three epochs for the N = 100 adaptive grid (blue) and the fixed GridPattern.dat grid (red). Tick marks along the top (adaptive, blue) and bottom (fixed, red) edges show individual zone boundaries. Dashed vertical lines mark the photosphere. The adaptive grid tracks the photosphere inward by shifting resolution from the outer layers to the interior as the ejecta evolve.