TITLE: Dune Engine — Falling Sand Sandbox FILE: 055-falling-sand.html === PROMPT (exact prompt used) === Create "Dune Engine — Falling Sand Sandbox", a cellular-automaton physics toy. A pixel-art canvas (each cell 3–4px) with elements: Sand (warm variations #e6c07b, #d8a95b), Water (#3d7ee0 with shimmer, flows sideways), Stone (static greys), Fire (flickers, rises, burns wood, turns water to steam), Wood (#8b5a2b), Steam (rises and condenses back into water), Oil (floats on water, highly flammable), Lava (turns sand into glass), and Plant (grows into water). Correct density-based interactions (sand sinks in water, oil floats). Desert-dusk UI palette: sand #f3e3c3, terracotta #c1440e, deep dusk blue #1f2a44. An element picker as a row of textured swatches with icons, brush-size slider, pause, clear, and "Scenes" (hourglass, volcano, oasis). Pointer/touch painting interpolated along the stroke. A tiny monospace readout of particle count and fps. Efficient: typed arrays, bottom-up updates with alternating direction, ImageData rendering. SHARED REQUIREMENTS (apply to every page in this 100-page collection): 1. One standalone HTML5 file. All CSS inline in