main section can have multiple layouts. For narrow windows everything is stacked up. On wider windows things are arranged in a grid - controls on left, map top-right and message log bottom-right. For shorter windows the whole page will scroll. For taller windows only the controls section will scroll so the map always stays in view. This isn't all that different to how things were before but it should work well at all reasonable screen sizes now.
Controls area is restructured into subsections in a way I think makes things more intuitive. Subsections are also collapsible, which can help with avoiding scrolling.
Form elements are labelled using label elements.
All form elements in the controls section are keyboard navigable and it can clearly be seen when an element has focus.
Still to do:
Fix timeout issues
Set up keyboard-friendly alternatives for adding and editing points and performing a measurement
Vary icon shape so the only distinction isn't colour.
Still to do: