/* 功能页 · 彩虹脊骨分支 */
.spine-head{padding:2rem 0;background:#fff;border-bottom:1px solid #e8e8e8}
.spine-head h1{font-size:clamp(1.45rem,3.5vw,1.95rem);font-weight:900;margin-bottom:.5rem}
.spine-head p{color:#555;max-width:600px;font-size:.94rem}
.lang-legend{display:flex;flex-wrap:wrap;gap:.35rem;margin-top:1rem}
.legend-item{font-size:.68rem;font-weight:700;padding:.2rem .5rem;color:#fff;border-radius:2px}

.spine-body{padding:2.5rem 0;background:#fafafa}
.spine-layout{display:grid;grid-template-columns:48px 1fr;gap:0;max-width:900px;margin:0 auto}
.spine-rail{display:flex;flex-direction:column}
.spine-block{flex:1;min-height:80px}
.spine-block.s1{background:#e74c3c}.spine-block.s2{background:#f39c12}
.spine-block.s3{background:#f1c40f}.spine-block.s4{background:#2ecc71}
.spine-block.s5{background:#3498db}.spine-block.s6{background:#9b59b6}

.spine-branches{display:flex;flex-direction:column;gap:0}
.branch{display:grid;grid-template-columns:24px 1fr;padding:1.5rem 0 1.5rem 1rem;border-bottom:1px solid #e0e0e0;align-items:start}
.branch-connector{width:24px;height:2px;margin-top:1rem;background:#ccc;position:relative}
.branch-connector::before{content:"";position:absolute;left:0;top:-6px;width:2px;height:14px;background:#ccc}
.branch:nth-child(odd){background:#fff}
.branch:nth-child(even){background:#f9f9f9}
.branch-tag{font-size:.65rem;font-weight:800;padding:.15rem .45rem;color:#fff;display:inline-block;margin-bottom:.4rem;border-radius:2px}
.branch h2{font-size:1.05rem;margin-bottom:.4rem}
.branch p{font-size:.86rem;color:#555;margin-bottom:.6rem}
.branch ul{font-size:.84rem;color:#666}
.branch li{padding:.2rem 0;padding-left:.85rem;position:relative}
.branch li::before{content:"›";position:absolute;left:0;font-weight:700}
.branch img{margin-top:.75rem;border:2px solid #ddd;max-width:300px}

.spine-extra{padding:2rem 0;background:#fff}
.extra-duo{display:grid;grid-template-columns:1fr 1fr;gap:1.5rem}
.extra-panel{border-top:4px solid;padding:1.25rem;background:#fafafa}
.extra-panel.ep1{border-top-color:#e74c3c}.extra-panel.ep2{border-top-color:#3498db}
.extra-panel h3{font-size:1rem;margin-bottom:.5rem}
.extra-panel li{font-size:.86rem;color:#555;padding:.25rem 0}

.spine-cta{text-align:center;padding:2.5rem 0;background:#1a1a2e;color:#fff}
.spine-cta h2{font-size:1.3rem;margin-bottom:1rem;font-weight:900}
.spine-cta a{display:inline-block;background:#e74c3c;color:#fff!important;padding:.7rem 1.6rem;font-weight:800;text-decoration:none!important;border-radius:4px}

@media(max-width:640px){
  .spine-layout{grid-template-columns:1fr}
  .spine-rail{flex-direction:row;height:8px}
  .spine-block{flex:1;min-height:8px}
  .branch-connector{display:none}
  .extra-duo{grid-template-columns:1fr}
}