/* Each chapter fills the space below the fixed navigation. Its existing
   padding is included; longer content remains in the normal page flow. */
main > section[id]{
  min-height:calc(100vh - var(--page-nav-height));
  min-height:calc(100svh - var(--page-nav-height));
  min-height:calc(100dvh - var(--page-nav-height));
  display:flex;
  flex-direction:column;
  justify-content:center;
}

/* The bridge has two parts. Give any extra space to its full-width image
   and message instead of introducing empty bands around the composition. */
#bridge{justify-content:flex-start}
#bridge > .family-feature{flex:1 0 auto}

/* Anchor navigation starts the chapter directly beneath the header. */
main > section[id],#access{scroll-margin-top:var(--page-nav-height)}