/* --- cover refinement --- */
.cover-inner{
  isolation:isolate;
}
.cover-inner:before{
  content:"";
  position:absolute;inset:14px;
  border:1px solid rgba(91,133,123,.08);
  border-radius:30px;
  pointer-events:none;z-index:-1;
}
.cover-kicker{opacity:.88}
.cover-enter{
  transition:transform .18s ease,box-shadow .18s ease,background .18s ease;
}
.cover-enter:hover{
  transform:translateY(-2px);
  box-shadow:0 10px 24px rgba(65,100,92,.08);
  background:#deefe9;
}

/* --- overall contents title --- */
.book-toc-head{
  position:relative;
  padding-left:18px;
}
.book-toc-head:before{
  content:"";
  position:absolute;left:0;top:5px;bottom:5px;width:3px;
  border-radius:99px;
  background:linear-gradient(#91c5ba,#d8bda5);
}
.book-toc-head h2{letter-spacing:.05em}

/* --- chapter cards: clearer click affordance --- */
.book-chapter-card{
  position:relative;
}
.book-chapter-card:before{
  content:"";
  position:absolute;right:17px;top:17px;
  width:7px;height:7px;border-radius:50%;
  background:#a7cec5;
  box-shadow:0 0 0 5px rgba(167,206,197,.12);
}
.book-chapter-card b{
  display:inline-flex;align-items:center;gap:5px;
  transition:gap .18s ease,color .18s ease;
}
.book-chapter-card:hover b{gap:9px;color:#447b71}
.book-chapter-icon{
  box-shadow:inset 0 1px 0 rgba(255,255,255,.85);
}

/* --- chapter hero hierarchy --- */
#chapter1Pane,#chapter2Pane{
  scroll-margin-top:20px;
}
.chapter-anchor{scroll-margin-top:80px}

/* --- internal net TOC --- */
.net-toc-card{
  position:relative;overflow:hidden;
}
.net-toc-card:after{
  content:"›";
  position:absolute;right:10px;top:50%;
  transform:translateY(-50%);
  color:#9ab8b1;font-size:17px;font-weight:400;
  transition:transform .18s ease,color .18s ease;
}
.net-toc-card:hover:after{
  transform:translate(2px,-50%);
  color:#6f9d94;
}

/* --- learning flow --- */
.toc-guide{
  box-shadow:inset 0 1px 0 rgba(255,255,255,.8);
}
.toc-guide span{
  box-shadow:0 3px 9px rgba(66,99,91,.05);
}

/* --- chapter return buttons: visual polish only --- */
.parent-toc-back{
  letter-spacing:.015em;
}
.parent-toc-back:focus-visible,
.book-chapter-card:focus-visible,
.cover-enter:focus-visible{
  outline:2px solid rgba(91,151,139,.55);
  outline-offset:3px;
}

/* --- softer section separation --- */
.net-divider{
  box-shadow:0 10px 30px rgba(64,98,90,.035);
}

/* --- mobile --- */
@media(max-width:700px){
  .cover-inner:before{inset:9px;border-radius:22px}
  .book-toc-head{padding-left:13px}
  .book-chapter-card:before{right:12px;top:12px}
  .net-toc-card:after{right:8px}
}