.crust-head{text-align:center;padding:2.5rem 0 1rem;background:linear-gradient(180deg,#101c28,#0c1824)}
.crust-head h1{font-size:clamp(1.35rem,3.2vw,1.85rem);font-weight:800;margin-bottom:.5rem;color:#d0e4f0}
.crust-head p{font-size:.92rem;color:#6a8aa0}
.crust-id{font-size:.7rem;color:#4ecdc4;letter-spacing:.12em;margin-top:.5rem;display:block;font-weight:800}

.cross-section{padding:2rem 0 3.5rem}
.section-diagram{display:flex;flex-direction:column;align-items:center;gap:0;max-width:680px;margin:0 auto}
.diagram-ring{
  width:100%;padding:1.35rem 1.5rem;border:1px solid #2a4a5a;position:relative;
  display:grid;grid-template-columns:120px 1fr;gap:1rem;align-items:center;
}
.diagram-ring::before{
  content:"";position:absolute;left:0;top:0;bottom:0;width:6px;
}
.diagram-ring.crust{background:#1a2838}
.diagram-ring.crust::before{background:linear-gradient(180deg,#c4845a,#8a5a3a)}
.diagram-ring.mantle{background:#142030}
.diagram-ring.mantle::before{background:linear-gradient(180deg,#2a6a8a,#1a4a6a)}
.diagram-ring.core{background:#0c1824;border-color:#4ecdc4}
.diagram-ring.core::before{background:#4ecdc4}
.ring-label{font-size:.68rem;font-weight:800;color:#4ecdc4;letter-spacing:.1em}
.diagram-ring h2{font-size:1.05rem;font-weight:800;margin-bottom:.4rem;color:#d0e4f0}
.diagram-ring p{font-size:.86rem;color:#6a8aa0;line-height:1.6;margin-bottom:.5rem}
.diagram-ring ul{margin-bottom:.5rem}
.diagram-ring li{font-size:.84rem;color:#6a8aa0;padding:.18rem 0 .18rem .9rem;position:relative}
.diagram-ring li::before{content:"◆";position:absolute;left:0;color:#4ecdc4;font-size:.5rem;top:.4rem}
.diagram-ring img{border:1px solid #2a4a5a;max-width:200px;margin-top:.5rem}

.crust-appendix{background:#101c28;border-top:2px solid #4ecdc4;border-bottom:2px solid #2a4a5a;padding:2.5rem 0}
.crust-pair{display:grid;grid-template-columns:1fr 1fr;gap:1.25rem}
.crust-block{background:#0c1824;border:1px solid #2a4a5a;padding:1.25rem}
.crust-block h3{font-size:.95rem;font-weight:800;color:#4ecdc4;margin-bottom:.6rem}
.crust-block li{font-size:.86rem;color:#6a8aa0;padding:.28rem 0}

.crust-cta{text-align:center;padding:2.5rem 1rem;background:#4ecdc4;color:#081018}
.crust-cta h2{font-size:1.15rem;font-weight:800;margin-bottom:.7rem}
.crust-cta a{display:inline-block;background:#081018;color:#4ecdc4!important;padding:.5rem 1.3rem;font-weight:800;text-decoration:none!important}

@media(max-width:640px){
  .diagram-ring{grid-template-columns:1fr}
  .crust-pair{grid-template-columns:1fr}
}