The picture is the coordinate space. Drag the headline around on it, drag the picture's corner, then pull the page width down to a phone and watch what happens.
Rooms with a long view over the water
headline is locked to this picture
Six rooms above the old chandlery, each looking straight down the estuary. Breakfast is at the long table, and the tide comes in under the window.
Nothing here is a breakpoint. The heading's position and size are percentages of the picture, so scaling is free. The only computed number is the width at which the picture gets too small for the text to stay readable, and because the percentage and the floor are both known when the site is published, that width can be written into the stylesheet as a fixed rule. The published page needs no JavaScript to behave this way.