{"tool":"Built-in image_gen","purpose":"Concept cover, not simulation data","asset":"/img/fdtd-algorithm-metalens/00-cover.png","prompt":"Create a refined wide 16:9 editorial scientific illustration for a Chinese advanced undergraduate tutorial on FDTD and dielectric metalenses. No text, no labels, no equations, no logos. Dark midnight navy background, luminous cyan and warm amber accents, precise elegant optics textbook cover with cinematic restrained 3D rendering. A flat circular array of many short dielectric nanopillars of varied diameters on a transparent thin planar substrate, in perspective. Parallel incident translucent planar wavefronts approach from the lower left, emerging converging spherical wavefront arcs above the plate converge toward a single small bright focus in upper right. A subtle translucent Cartesian computational grid occupies part of the air surrounding the plate, evoking spatial discretization, but not claimed as an exact Yee lattice. Make the metasurface visibly flat, not a curved glass lens. Clean composition, generous negative space, physically inspired conceptual artwork rather than simulation data. No rainbow heatmap, no fake charts, no multiple focus points.","final_edit_prompt":"Edit this scientific metalens cover image. Preserve its composition, nanopillar array, cyan incoming wavefronts, amber converging light and focal point, and computational grid. The original has unintended partially transparent cloudy areas. Replace ALL transparency with a consistent very dark midnight navy background (#06101a); make the entire rectangular image fully opaque, including all corners, while keeping the luminous scene. No white or grey clouds, no cloudy texture, no text. This is an opaque blog cover, not a transparent cutout. Do not add any other features."}