CSS rendered coordinates and flow
Aspect ratios, containing blocks, sticky positions and stacking boundaries.
Reserve a proportional box before content arrives
Let one automatic dimension follow a preferred 16:9 ratio.
Explain the gap below an inline box
Compare baseline alignment with bottom alignment inside a fixed line box.
Anchor an absolute note to its own panel
Identify the containing block that gives top and right offsets their reference.
Keep a heading sticky inside its scroll container
Observe a heading at scrollTop 0 and 80 inside a120px local scrollport.
See why a huge z-index stays behind a sibling
Hit-test overlapping native boxes to inspect a nested stacking context.
Distinguish transformed bounds from the layout slot
Compare a translated element’s measured bounds with the unchanged next row.
Compare hidden content with a removed layout box
Measure the difference between visibility:hidden and display:none.