Title: Pocket A-Series Paper Explorer

Goal Build a small offline browser tool that makes ISO A0-A6 paper sizes easy to compare visually. It should feel like a pocket reference, not a full design application. Deliverable - Exactly one self-contained file named index.html. - Maximum file size 40 KB. - It must work offline in a modern browser with no build step. Requirements 1. Provide a selector for A0 through A6 and display the selected sheet's width and height in millimetres. 2. Render a clearly labelled proportional rectangle for the selected sheet using the A-series 1:square-root-of-2 shape. 3. Show the selected sheet's area fraction relative to A0: 1, 1/2, 1/4, 1/8, 1/16, 1/32, or 1/64. 4. Include a compare control for choosing a second size and show the two sheets at a common visual scale, overlaid or side by side. 5. Include portrait/landscape switching that swaps displayed dimensions without changing the underlying sheet size. 6. Use this fixed millimetre table: A0 841x1189, A1 594x841, A2 420x594, A3 297x420, A4 210x297, A5 148x210, A6 105x148. 7. Make controls keyboard accessible, provide visible focus styles, and keep the interface usable from 360 px to 1200 px wide. 8. Include one short explanatory sentence that each next A size has half the area of the previous size. Negative scope No external libraries, fonts, images, network requests, tracking, storage, accounts, uploads, print ordering, build tools, or unrelated paper standards. Do not add advertising or links that perform actions. Acceptance gates - The submission contains only index.html and stays under 40 KB. - It opens offline without console-blocking errors or missing assets. - All seven sizes, dimensions, area fractions, comparison, and orientation behaviour are present and internally correct. - Controls have labels, keyboard operation, visible focus, and responsive layout. - No network-capable or privacy-invasive code is present. Judging: 100 points - Functional and dimensional correctness: 40 - Compliance with the required behaviour and packaging: 25 - Visual clarity and accessibility: 20 - Craft and delightful restraint: 15 Tie-breaker Prefer the eligible tool whose values and behaviour are easiest to verify from both the interface and readable source.