Build a single self-contained HTML file that renders an endless low-poly terrain flyover. Requirements: a procedurally generated low-poly landscape (chunky flat-shaded triangles — hills, valleys, maybe water) built from noise, that regenerates/extends infinitely so the world never runs out as you move; a camera that flies forward continuously over the terrain, with the mouse steering the direction of flight (look around / bank); a low-poly art direction with tasteful, cohesive coloring (e.g. height-based terrain colors), soft lighting, and atmospheric fog or a gradient sky so distant geometry fades nicely; and smooth, stable performance with no popping or stutter as new terrain streams in. It should look genuinely impressive and relaxing to fly through. You may load Three.js from a CDN. Return ONLY a single complete self-contained HTML file, no markdown fences, no explanation.
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