Canvas
Put .canvas on pg-toolbar, pg-main or pg-main-footer. Each
paints a rounded inset surface at the tone --canvas. Adjacent canvas
regions flatten the corners they share. Add or remove a region and the
corners re-solve.
Rise
.rise takes --rise hundredths of the small viewport as a minimum
block size:
html
<div class="column rise" style="--rise: 55;">…</div>
Content taller than the share pushes past it and the canvas scrolls. The landing demo opens on a rise.