Stage 7 — degradation. Three quality tiers (high: DPR ≤ 2, GTAO, 4096 shadows; balanced: DPR ≤ 1.5; fast: DPR 1, no GTAO, 2048 shadows). The tier drops automatically after 3 s of frames slower than 25 ms. A static poster shows first and stays if WebGL is missing or lost. Reduced motion means no flight, instant light changes and no damping. The scene renders only when something changes. Keyboard: Tab through every control, focus the canvas to orbit with the arrow keys and zoom with +/−.