TITLE: Elementa FILE: 028-periodic-table.html === PROMPT (exact prompt used) === Design "Elementa", an interactive periodic table of all 118 elements with a premium dark look (#0d1117). Each tile shows atomic number, symbol and name, coloured by category with a harmonious palette (alkali metals #ff6b6b, alkaline earth #ffa94d, transition metals #ffd43b, post-transition #69db7c, metalloids #38d9a9, nonmetals #4dabf7, halogens #748ffc, noble gases #da77f2, lanthanides #f783ac, actinides #e599f7) at soft opacity with glowing borders. Use standard atomic weights, rounded sensibly. The layout follows the standard 18-column table with the f-block below; on narrow phones the table pans horizontally inside its own scroll container (the page itself must not overflow). Interaction: hovering or focusing a tile fills a large detail panel with an animated Bohr-model shell diagram (electrons orbiting on shells with correct per-shell counts), category, atomic mass and state at room temperature; the category legend buttons filter and highlight; a search box jumps to an element. Keyboard navigable with arrow keys. SHARED REQUIREMENTS (apply to every page in this 100-page collection): 1. One standalone HTML5 file. All CSS inline in