Prompt

Make a converter for length. Make it a single HTML file that opens in a browser with nothing to install and no other files. Put the CSS and JavaScript inside it. Do not use image files or any external address; use emoji or letters if you need a symbol.

Put two boxes side by side, one for each unit, starting with centimetres and inches. Typing in either one updates the other as I type. No convert button.

Let me pick different units from a short list next to each box. Include about six units for this kind of measurement.

Round the answer to something a person would actually say — not fifteen decimal places. Show more decimals only when the number is very small.

When you are done, type in both boxes in turn and check neither one fights the other while you type.