/* steps.css — 台阶式产品展示（sticky 舞台 + 逐级切换）
   结构约定（配合 steps.js 使用）：
   <div class="st-steps">                       <- 滚动区（JS 挂载点）
     <div class="st-stage">                     <- sticky 舞台（必须是最前子元素）
       <div class="st-list">                    <- 左：常驻列表
         <div class="st-bar"></div>             <- 移动标题竖线
         <div class="st-item is-product">       <- L0 产品级
           <div class="st-title">产品名</div>
           <div class="st-body">一句话介绍</div>
         </div>
         <div class="st-item">                  <- L1..Ln 功能级
           <div class="st-title"><span class="st-num">01</span>功能名</div>
           <div class="st-body">说明</div>
         </div>
         ...
       </div>
       <div class="st-booth">                   <- 右：组件区（无承托盘）
         <div class="st-comp">…任意组件…</div>   <- 与 st-item 一一对应
         ...
       </div>
     </div>
     <div class="st-anchor"></div> × (n+1)      <- 锚点只提供滚动长度
   </div>
   主题色：在 .st-steps 上设 --st-cat / --st-cat-soft。
   铁律：.st-steps 及其祖先不许用 overflow:hidden（会废掉 sticky），用 overflow:clip。 */
.st-steps { position: relative; }
.st-anchor { height: 55svh; }
.st-stage {
  position: sticky; top: 0; height: 100svh;
  display: grid; grid-template-columns: minmax(380px, .9fr) 1.35fr;
  align-items: center; gap: 32px;
  max-width: 1360px; margin: 0 auto; padding: 0 48px;
}

/* 左：列表 + 移动竖线。列表顶部钉死（不再随展开居中求高），
   大标题位置跨级固定，只有下面的条目在动 */
.st-list { position: relative; padding-left: 22px; align-self: start; margin-top: 18svh; }
.st-bar {
  position: absolute; left: 0; top: 0; width: 3px; height: 26px; border-radius: 2px;
  background: var(--st-cat, #0071e3); opacity: .9;
  transition: transform .5s cubic-bezier(.2,.7,.3,1), height .5s cubic-bezier(.2,.7,.3,1);
}
.st-item { padding: 10px 0; transition: opacity .4s; cursor: pointer; }
.st-item .st-title { font-size: 17px; font-weight: 600; color: rgba(0,0,0,.44);
  transition: color .4s, font-size .4s; display: flex; align-items: baseline; }
.st-item .st-num { display: inline-block; width: 30px; flex: none;
  font-size: 12.5px; font-weight: 600; color: rgba(0,0,0,.44); letter-spacing: .08em;
  transition: color .4s; }
.st-item .st-body { max-height: 0; overflow: hidden; opacity: 0;
  transition: max-height .55s cubic-bezier(.2,.7,.3,1), opacity .45s, margin .45s;
  font-size: 15px; color: rgba(0,0,0,.68); line-height: 1.65;
  margin-top: 0; margin-left: 30px; /* 与标题文字对齐，不与序号对齐 */ }
.st-item:hover .st-title { color: rgba(0,0,0,.68); }
.st-item.active .st-title { color: #1d1d1f; font-size: 24px; }
.st-item.active .st-num { color: var(--st-cat, #0071e3); }
.st-item.active .st-body { max-height: 130px; opacity: 1; margin-top: 8px; }
.st-item.done .st-title { color: rgba(0,0,0,.68); }
.st-item.is-product .st-title { font-size: 26px; letter-spacing: -.02em; }
.st-item.is-product .st-body { margin-left: 0; }
.st-item.is-product.active .st-title { font-size: 32px; }

/* 右：组件区（无承托盘 + 分类色氛围光晕） */
.st-booth { position: relative; height: min(78svh, 720px); }
.st-booth::before {
  content: ""; position: absolute; inset: -8%; pointer-events: none;
  background: radial-gradient(45% 45% at 55% 45%, var(--st-cat-soft, rgba(0,113,227,.12)), transparent 70%);
  opacity: .8;
}
/* 切换要干脆：快进快出，不拖泥带水 */
.st-comp {
  position: absolute; inset: 0; display: flex; align-items: center; justify-content: center;
  opacity: 0; transform: translateY(14px) scale(.985);
  transition: opacity .22s ease-out, transform .28s cubic-bezier(.2,.9,.25,1);
  pointer-events: none; padding: 12px;
}
.st-comp.active { opacity: 1; transform: none; pointer-events: auto; }
.st-comp.leaving { opacity: 0; transform: none; transition: opacity .16s ease-out, transform .16s ease-out; }

@media (max-width: 860px) {
  .st-stage { grid-template-columns: 1fr; gap: 16px; align-content: center; padding: 0 22px; }
  .st-list { align-self: auto; margin-top: 0; }
  .st-booth { height: 44svh; }
}
@media (prefers-reduced-motion: reduce) {
  .st-comp, .st-item .st-title, .st-item .st-body, .st-bar { transition: none; }
}