/* ============================================================
   Case Studies & Tutorials — /case-studies 与 /case-studies/{slug}
   ------------------------------------------------------------
   261110++ 整份沿用设计稿 assets/cs.css(未改动任何一条规则),只改文件名:
   站内 CSS 按页面命名(shopping-guide.css / dropship.css …),cs.css 太泛。
   两个命名空间:
     .cs-   列表页(hero / featured / 筛选 / 卡片 / 学习路径)
     .csd-  详情页(头部 / 正文版式 / 目录 / At a glance / 分享)
   依赖:style.css 的 CSS 变量(--brand/--ink/--muted/--line/--radius-lg/--blue)
        与 dist.css 的 .da-*(区块外壳、按钮、CTA),因此两个视图都要引这两个文件。
   注意:pages.css 里已有 .cs-empty(侧栏筛选的空态),含义相近;本文件在它之后加载,
        同属性以这里为准(display:none / .show 切块),不会互相打架。
   ============================================================ */

.cs-wrap{overflow:hidden}
.cs-wrap .container{max-width:1180px}

.reveal{opacity:0;transform:translateY(22px);transition:opacity .7s cubic-bezier(.2,.7,.2,1),transform .7s cubic-bezier(.2,.7,.2,1)}
.reveal.in{opacity:1;transform:none}
.reveal.d1{transition-delay:.07s}.reveal.d2{transition-delay:.14s}.reveal.d3{transition-delay:.21s}
@media(prefers-reduced-motion:reduce){.reveal{opacity:1;transform:none;transition:none}}

/* ============================================================
   HERO
   ============================================================ */
.cs-hero{position:relative;color:#fff;isolation:isolate;
  background:linear-gradient(158deg,#0d1420 0%,#2a0d18 52%,#0b1017 100%)}
.cs-hero::before{content:"";position:absolute;inset:-20% -10% 0;z-index:-2;
  background:radial-gradient(560px 400px at 84% 2%,rgba(185,31,66,.5),transparent 60%),
             radial-gradient(520px 380px at 6% 100%,rgba(46,108,246,.36),transparent 62%);
  filter:blur(6px);animation:csAur 15s ease-in-out infinite alternate}
@keyframes csAur{0%{transform:translate3d(0,0,0)}100%{transform:translate3d(3%,-2%,0) scale(1.05)}}
.cs-hero::after{content:"";position:absolute;inset:0;z-index:-1;opacity:.5;
  background-image:radial-gradient(circle at 1px 1px,rgba(255,255,255,.15) 1px,transparent 0);
  background-size:26px 26px;-webkit-mask-image:linear-gradient(180deg,#000,transparent 86%);
          mask-image:linear-gradient(180deg,#000,transparent 86%)}
.cs-hero-inner{position:relative;padding:60px 0 66px;text-align:center;max-width:760px;margin:0 auto}
.cs-hero .da-eyebrow{color:#ffd7e2;background:rgba(255,255,255,.1)}
.cs-hero h1{font-size:clamp(2rem,4.2vw,3.1rem);font-weight:800;letter-spacing:-.02em;margin:18px 0 12px;color:#fff}
.cs-hero h1 em{font-style:normal;background:linear-gradient(90deg,#ff9db6,#ffd0a3);-webkit-background-clip:text;
  background-clip:text;-webkit-text-fill-color:transparent}
.cs-hero p{font-size:1.08rem;color:rgba(255,255,255,.8);margin:0 auto 24px;max-width:600px}
.cs-hsearch{position:relative;max-width:480px;margin:0 auto}
.cs-hsearch i{position:absolute;left:18px;top:50%;transform:translateY(-50%);color:var(--muted);font-size:1.1rem}
.cs-hsearch input{width:100%;border:0;border-radius:999px;padding:15px 20px 15px 48px;font-size:1rem;font-family:inherit;
  color:var(--ink);background:#fff;box-shadow:0 20px 50px rgba(0,0,0,.35)}
.cs-hsearch input:focus{outline:none;box-shadow:0 0 0 4px rgba(255,255,255,.22),0 20px 50px rgba(0,0,0,.35)}

/* ============================================================
   FEATURED / SPOTLIGHT
   ============================================================ */
.cs-feat{display:grid;grid-template-columns:1.15fr .85fr;gap:0;background:#fff;border:1px solid var(--line);
  border-radius:var(--radius-lg);overflow:hidden;box-shadow:0 26px 60px rgba(20,32,43,.1)}
@media(max-width:850px){.cs-feat{grid-template-columns:1fr}}
.cs-feat-media{position:relative;min-height:300px;overflow:hidden}
.cs-feat-media img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover}
.cs-feat-media .veil{position:absolute;inset:0;background:linear-gradient(120deg,rgba(15,14,20,.25),rgba(185,31,66,.35))}
.cs-feat-media .play{position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);width:78px;height:78px;border-radius:50%;
  background:rgba(255,255,255,.95);display:grid;place-items:center;color:var(--brand);font-size:1.8rem;box-shadow:0 18px 44px rgba(0,0,0,.4)}
.cs-feat-media .play i{margin-left:4px}
.cs-feat-media .play::before{content:"";position:absolute;inset:0;border-radius:50%;border:2px solid rgba(255,255,255,.55);animation:csPulse 2.6s ease-out infinite}
@keyframes csPulse{0%{transform:scale(1);opacity:.6}100%{transform:scale(1.5);opacity:0}}
.cs-feat:hover .cs-feat-media .play{transform:translate(-50%,-50%) scale(1.08);transition:transform .2s ease}
.cs-feat-media .dur{position:absolute;bottom:16px;right:16px;background:rgba(0,0,0,.6);color:#fff;border-radius:999px;padding:6px 12px;font-size:.8rem;font-weight:700}
.cs-feat-body{padding:34px 36px;display:flex;flex-direction:column;justify-content:center}
.cs-feat-body .k{display:inline-flex;align-items:center;gap:7px;align-self:flex-start;font-size:.72rem;font-weight:800;
  letter-spacing:.1em;text-transform:uppercase;color:var(--brand);background:var(--brand-soft,#fbecef);border-radius:999px;padding:6px 13px}
.cs-feat-body h2{font-size:clamp(1.4rem,2.6vw,1.9rem);font-weight:800;letter-spacing:-.02em;color:var(--ink);margin:14px 0 10px;line-height:1.2}
.cs-feat-body p{color:var(--muted);font-size:1rem;line-height:1.65;margin:0 0 18px}
.cs-feat-stats{display:flex;flex-wrap:wrap;gap:8px 20px;margin-bottom:20px;font-size:.86rem;color:var(--body)}
.cs-feat-stats span{display:inline-flex;align-items:center;gap:7px}
.cs-feat-stats i{color:var(--brand)}

/* ============================================================
   FILTER + GRID
   ============================================================ */
.cs-filter{display:flex;flex-wrap:wrap;gap:8px;justify-content:center;margin-bottom:28px}
.cs-chip{border:1px solid var(--line);background:#fff;color:var(--body);border-radius:999px;padding:9px 17px;
  font-size:.88rem;font-weight:600;cursor:pointer;transition:.15s}
.cs-chip:hover{border-color:var(--brand);color:var(--brand)}
.cs-chip.on{background:linear-gradient(135deg,var(--brand),var(--brand-dark));color:#fff;border-color:transparent;
  box-shadow:0 8px 18px rgba(185,31,66,.24)}

.cs-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:22px}
@media(max-width:900px){.cs-grid{grid-template-columns:repeat(2,1fr)}}
@media(max-width:575px){.cs-grid{grid-template-columns:1fr}}
.cs-card{display:flex;flex-direction:column;background:#fff;border:1px solid var(--line);border-radius:16px;overflow:hidden;
  text-decoration:none;transition:transform .2s ease,box-shadow .2s ease,border-color .2s ease}
.cs-card:hover{transform:translateY(-6px);box-shadow:0 22px 46px rgba(20,32,43,.12);border-color:transparent}
.cs-card.hide{display:none}
.cs-thumb{position:relative;aspect-ratio:16/10;overflow:hidden;background:var(--bg-soft)}
.cs-thumb img{width:100%;height:100%;object-fit:cover;transition:transform .45s ease}
.cs-card:hover .cs-thumb img{transform:scale(1.07)}
.cs-thumb .veil{position:absolute;inset:0;background:linear-gradient(180deg,transparent 45%,rgba(15,14,20,.5))}
.cs-tag{position:absolute;top:12px;left:12px;font-size:.7rem;font-weight:800;letter-spacing:.04em;text-transform:uppercase;
  color:#fff;background:rgba(185,31,66,.92);border-radius:999px;padding:5px 11px}
.cs-type{position:absolute;top:12px;right:12px;width:30px;height:30px;border-radius:50%;background:rgba(15,14,20,.6);
  color:#fff;display:grid;place-items:center;font-size:.82rem}
.cs-play{position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);width:52px;height:52px;border-radius:50%;
  background:rgba(255,255,255,.92);display:grid;place-items:center;color:var(--brand);font-size:1.2rem;opacity:0;transition:.2s}
.cs-play i{margin-left:3px}
.cs-card:hover .cs-play{opacity:1}
.cs-card-body{padding:18px 20px 20px;display:flex;flex-direction:column;flex:1}
.cs-card-body h3{font-size:1.05rem;font-weight:700;color:var(--ink);margin:0 0 7px;line-height:1.35}
.cs-card-body p{font-size:.88rem;color:var(--muted);line-height:1.55;margin:0 0 14px;flex:1}
.cs-meta{display:flex;align-items:center;gap:14px;font-size:.78rem;color:var(--muted);font-weight:600}
.cs-meta span{display:inline-flex;align-items:center;gap:5px}
.cs-meta .go{margin-left:auto;color:var(--brand);font-weight:700}

.cs-empty{display:none;text-align:center;padding:50px 10px;color:var(--muted)}
.cs-empty.show{display:block}
.cs-empty i{font-size:2.2rem;color:var(--brand);display:block;margin-bottom:8px}

/* ============================================================
   LEARNING PATHS
   ============================================================ */
.cs-paths{display:grid;grid-template-columns:repeat(3,1fr);gap:22px}
@media(max-width:850px){.cs-paths{grid-template-columns:1fr}}
.cs-path{position:relative;border-radius:var(--radius-lg);padding:30px 28px;color:#fff;overflow:hidden;
  transition:transform .2s ease,box-shadow .2s ease}
.cs-path:hover{transform:translateY(-6px);box-shadow:0 26px 54px rgba(20,32,43,.2)}
.cs-path.p1{background:linear-gradient(150deg,#2a0d18,#4a1226)}
.cs-path.p2{background:linear-gradient(150deg,#0f2318,#19422b)}
.cs-path.p3{background:linear-gradient(150deg,#0f1828,#1a2b47)}
.cs-path .ic{width:50px;height:50px;border-radius:14px;display:grid;place-items:center;font-size:1.4rem;
  background:rgba(255,255,255,.14);margin-bottom:16px}
.cs-path h3{font-size:1.2rem;font-weight:800;margin:0 0 6px}
.cs-path p{font-size:.9rem;color:rgba(255,255,255,.76);line-height:1.6;margin:0 0 16px}
.cs-path .steps{list-style:none;padding:0;margin:0 0 18px}
.cs-path .steps li{display:flex;gap:9px;align-items:center;font-size:.86rem;color:rgba(255,255,255,.9);padding:5px 0}
.cs-path .steps li i{color:#9ef5c4}
.cs-path .go{display:inline-flex;align-items:center;gap:7px;font-size:.88rem;font-weight:700;color:#fff;text-decoration:none;
  background:rgba(255,255,255,.14);border-radius:10px;padding:9px 16px;transition:background .15s}
.cs-path .go:hover{background:rgba(255,255,255,.24);color:#fff}
.cs-path .n{position:absolute;top:22px;right:26px;font-size:2.4rem;font-weight:800;opacity:.14}

/* ============================================================
   CASE STUDY DETAIL  (case-study-detail.html)
   Prefix: csd-
   ============================================================ */
.csd-wrap{overflow:hidden}
.csd-head{text-align:center;max-width:760px;margin:0 auto;padding:10px 0 30px}
.csd-tag{display:inline-flex;align-items:center;gap:7px;font-size:.74rem;font-weight:800;letter-spacing:.1em;text-transform:uppercase;
  color:var(--brand);background:var(--brand-soft,#fbecef);border-radius:999px;padding:7px 14px}
.csd-head h1{font-size:clamp(1.9rem,4vw,2.9rem);font-weight:800;letter-spacing:-.025em;color:var(--ink);margin:16px 0 12px;line-height:1.12}
.csd-head .sub{font-size:1.1rem;color:var(--muted);line-height:1.6;margin:0 0 20px}
.csd-meta{display:flex;flex-wrap:wrap;gap:8px 22px;justify-content:center;align-items:center;font-size:.88rem;color:var(--body)}
.csd-meta .who{display:inline-flex;align-items:center;gap:9px;font-weight:600}
.csd-meta .who img{width:34px;height:34px;border-radius:50%;object-fit:cover}
.csd-meta .d{display:inline-flex;align-items:center;gap:6px;color:var(--muted)}
.csd-meta .d i{color:var(--brand)}

/* feature image */
.csd-feature{position:relative;border-radius:var(--radius-lg);overflow:hidden;box-shadow:0 30px 70px rgba(20,32,43,.14);
  aspect-ratio:21/9;background:var(--bg-soft)}
.csd-feature img{width:100%;height:100%;object-fit:cover;display:block}
@media(max-width:700px){.csd-feature{aspect-ratio:16/10}}

/* image / figure placeholder */
.csd-ph{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:8px;height:100%;min-height:200px;
  border:2px dashed var(--line);background:var(--bg-soft);color:var(--muted);text-align:center}
.csd-ph i{font-size:2.2rem;color:#c3cedb}
.csd-ph b{font-size:.95rem;color:var(--body)}
.csd-ph span{font-size:.82rem}

/* layout */
.csd-layout{display:grid;grid-template-columns:1fr 290px;gap:46px;max-width:1040px;margin:0 auto}
@media(max-width:900px){.csd-layout{grid-template-columns:1fr;gap:30px}}

/* article typography */
.csd-article{min-width:0;font-size:1.02rem;line-height:1.8;color:var(--body)}
.csd-article h2{font-size:1.5rem;font-weight:800;color:var(--ink);letter-spacing:-.01em;margin:34px 0 12px;scroll-margin-top:84px}
.csd-article h2:first-child{margin-top:0}
.csd-article h3{font-size:1.15rem;font-weight:700;color:var(--ink);margin:24px 0 8px}
.csd-article p{margin:0 0 16px}
.csd-article a{color:var(--brand);font-weight:600}
.csd-article ul,.csd-article ol{margin:0 0 18px;padding-left:4px;list-style:none}
.csd-article ul li,.csd-article ol li{position:relative;padding:5px 0 5px 28px}
.csd-article ul li::before{content:"";position:absolute;left:4px;top:13px;width:8px;height:8px;border-radius:50%;background:var(--brand)}
.csd-article ol{counter-reset:ol}
.csd-article ol li{counter-increment:ol}
.csd-article ol li::before{content:counter(ol);position:absolute;left:0;top:4px;width:22px;height:22px;border-radius:50%;
  background:var(--brand-soft,#fbecef);color:var(--brand);font-size:.76rem;font-weight:800;display:grid;place-items:center}
.csd-article figure{margin:22px 0}
.csd-article figure .shot{border-radius:14px;overflow:hidden;border:1px solid var(--line)}
.csd-article figure img{width:100%;display:block}
.csd-article figcaption{font-size:.82rem;color:var(--muted);text-align:center;margin-top:9px}
.csd-lead{font-size:1.16rem;line-height:1.7;color:var(--ink);font-weight:500;margin:0 0 22px}

.csd-quote{margin:26px 0;padding:22px 26px;border-left:4px solid var(--brand);background:var(--brand-soft,#fbecef);
  border-radius:0 14px 14px 0}
.csd-quote p{font-size:1.18rem;font-weight:600;color:var(--ink);line-height:1.55;margin:0 0 8px}
.csd-quote cite{font-style:normal;font-size:.86rem;color:var(--muted);font-weight:600}

.csd-callout{display:flex;gap:13px;align-items:flex-start;background:#fff;border:1px solid var(--line);border-left:4px solid var(--blue);
  border-radius:12px;padding:16px 18px;margin:22px 0}
.csd-callout i{color:var(--blue);font-size:1.3rem;margin-top:1px}
.csd-callout b{color:var(--ink)}

/* results band */
.csd-results{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin:26px 0}
@media(max-width:575px){.csd-results{grid-template-columns:1fr}}
.csd-res{background:#fff;border:1px solid var(--line);border-radius:14px;padding:22px 20px;text-align:center}
.csd-res b{display:block;font-size:2rem;font-weight:800;letter-spacing:-.02em;color:var(--brand);line-height:1}
.csd-res span{font-size:.84rem;color:var(--muted);display:block;margin-top:5px}

/* sidebar */
.csd-aside{position:sticky;top:86px;align-self:start}
@media(max-width:900px){.csd-aside{position:static}}
.csd-box{background:#fff;border:1px solid var(--line);border-radius:14px;padding:20px;margin-bottom:16px}
.csd-box h4{font-size:.78rem;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);margin:0 0 12px}
.csd-toc a{display:block;font-size:.9rem;color:var(--body);text-decoration:none;padding:6px 0 6px 13px;border-left:2px solid var(--line);
  transition:.15s}
.csd-toc a:hover,.csd-toc a.on{color:var(--brand);border-color:var(--brand)}
.csd-facts div{display:flex;justify-content:space-between;gap:10px;font-size:.88rem;padding:7px 0;border-bottom:1px dashed var(--line)}
.csd-facts div:last-child{border-bottom:0}
.csd-facts span{color:var(--muted)}.csd-facts b{color:var(--ink);text-align:right}
.csd-share{display:flex;gap:8px}
.csd-share a{width:38px;height:38px;border-radius:10px;border:1px solid var(--line);display:grid;place-items:center;
  color:var(--body);text-decoration:none;transition:.15s}
.csd-share a:hover{border-color:var(--brand);color:var(--brand)}
.csd-cta-box{background:linear-gradient(150deg,#2a0d18,#4a1226);color:#fff;border:0}
.csd-cta-box h4{color:#ff9db6}
.csd-cta-box p{font-size:.88rem;color:rgba(255,255,255,.8);line-height:1.55;margin:0 0 14px}
.csd-cta-box .b{display:inline-flex;align-items:center;gap:7px;background:#fff;color:var(--brand-dark);font-weight:700;font-size:.88rem;
  border-radius:10px;padding:10px 16px;text-decoration:none}