/* ==========================================================================
   速学乐 UV · 课程兑换平台
   设计语言：印刷厂纸张底色 + CMYK 四色点缀 + 墨黑主色
   ========================================================================== */

/* ---------- 1. 变量与重置 ---------- */
:root {
  --ink: #12161c;
  --ink-soft: #2b323b;
  --muted: #6d7480;
  --faint: #9aa1ab;
  --paper: #f7f5f0;
  --paper-2: #efece4;
  --card: #ffffff;
  --line: rgba(18, 22, 28, 0.1);
  --line-strong: rgba(18, 22, 28, 0.18);
  --c: #00a0df;
  --m: #e6007e;
  --y: #ffc400;
  --k: #12161c;
  --green: #0f8a5f;
  --green-bg: #e9f7f0;
  --red: #c0392b;
  --red-bg: #fdf0ee;
  --radius: 18px;
  --radius-sm: 12px;
  --shadow-sm: 0 1px 2px rgba(18, 22, 28, 0.05), 0 6px 16px rgba(18, 22, 28, 0.04);
  --shadow: 0 2px 6px rgba(18, 22, 28, 0.05), 0 20px 50px rgba(18, 22, 28, 0.09);
  --font: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Hiragino Sans GB", "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SFMono-Regular", "JetBrains Mono", Consolas, "Courier New", monospace;
  --shell: 1140px;
  --ease: cubic-bezier(0.16, 1, 0.3, 1);
}

*,
*::before,
*::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  opacity: 0.5;
  background-image: radial-gradient(rgba(18, 22, 28, 0.055) 0.6px, transparent 0.6px);
  background-size: 4px 4px;
}

img, svg, video { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; }
h1, h2, h3, h4, p, ul, ol, figure { margin: 0; }
ul, ol { padding: 0; list-style: none; }
input, textarea, select { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--c); outline-offset: 3px; }

.shell {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 24px;
}
.narrow { max-width: 760px; }

.skip-link {
  position: absolute;
  left: -9999px;
  top: 8px;
  padding: 8px 14px;
  background: var(--ink);
  color: #fff;
  border-radius: 8px;
  z-index: 99;
}
.skip-link:focus { left: 12px; }

.icon { flex: none; }

/* ---------- 2. 品牌标记 ---------- */
.mark {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2.5px;
  width: 27px;
  height: 27px;
  flex: none;
}
.mark i { border-radius: 1.5px; background: var(--ink); }
.mark i:nth-child(3n + 1) { background: var(--c); }
.mark i:nth-child(3n + 2) { background: var(--m); }
.mark i:nth-child(3n + 3) { background: var(--y); }
.mark i:nth-child(5) { background: var(--ink); }
.mark i:nth-child(1) { border-radius: 50%; }
.mark i:nth-child(9) { border-radius: 50%; }
.mark--small { width: 20px; height: 20px; gap: 2px; }
.mark--large { width: 40px; height: 40px; gap: 4px; }

/* ---------- 3. 顶栏 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(247, 245, 240, 0.86);
  backdrop-filter: saturate(1.4) blur(14px);
  -webkit-backdrop-filter: saturate(1.4) blur(14px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex;
  align-items: center;
  gap: 28px;
  height: 68px;
}
.brand { display: flex; align-items: center; gap: 11px; }
.brand-text { display: flex; flex-direction: column; line-height: 1.1; }
.brand-text b { font-size: 16px; font-weight: 750; letter-spacing: 0.01em; }
.brand-text em {
  font-style: normal;
  font-size: 9px;
  letter-spacing: 0.2em;
  color: var(--faint);
  text-transform: uppercase;
  margin-top: 3px;
}
.nav { display: flex; align-items: center; gap: 4px; margin-left: auto; }
.nav-link {
  position: relative;
  padding: 8px 12px;
  border-radius: 9px;
  font-size: 14px;
  color: var(--muted);
  transition: color 0.2s, background 0.2s;
}
.nav-link:hover { color: var(--ink); background: rgba(18, 22, 28, 0.04); }
.nav-link.is-active { color: var(--ink); font-weight: 650; }
.nav-link.is-active::after {
  content: "";
  position: absolute;
  left: 50%;
  bottom: 1px;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--m);
  transform: translateX(-50%);
}
.header-cta {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  height: 38px;
  padding: 0 15px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  font-size: 13px;
  font-weight: 600;
  background: rgba(255, 255, 255, 0.6);
  transition: background 0.2s, transform 0.2s var(--ease), border-color 0.2s;
}
.header-cta:hover { background: #fff; border-color: var(--ink); transform: translateY(-1px); }
.header-cta .icon { width: 16px; height: 16px; color: var(--m); }

/* ---------- 4. 按钮 / 标签 / 表单 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  height: 52px;
  padding: 0 24px;
  border: 1px solid transparent;
  border-radius: 14px;
  font-size: 15px;
  font-weight: 650;
  letter-spacing: 0.01em;
  cursor: pointer;
  transition: transform 0.22s var(--ease), box-shadow 0.22s, background 0.2s, border-color 0.2s;
  white-space: nowrap;
}
.btn .icon { width: 18px; height: 18px; }
.btn:hover { transform: translateY(-2px); }
.btn:active { transform: translateY(0); }
.btn--ink { background: var(--ink); color: #fff; box-shadow: 0 6px 20px rgba(18, 22, 28, 0.18); }
.btn--ink:hover { box-shadow: 0 12px 30px rgba(18, 22, 28, 0.24); }
.btn--ghost { background: transparent; border-color: var(--line-strong); color: var(--ink); }
.btn--ghost:hover { background: #fff; border-color: var(--ink); }
.btn--paper { background: #fff; color: var(--ink); }
.btn--paper:hover { box-shadow: var(--shadow); }
.btn--block { width: 100%; }
.btn--sm { height: 40px; padding: 0 15px; font-size: 13px; border-radius: 11px; }
.btn--sm .icon { width: 16px; height: 16px; }
.btn--lg { height: 56px; font-size: 16px; }
.btn[disabled] { opacity: 0.6; cursor: progress; transform: none; }

.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  font-weight: 600;
  color: var(--m);
  white-space: nowrap;
}
.link-arrow .icon { width: 18px; height: 18px; transition: transform 0.2s var(--ease); }
.link-arrow:hover .icon { transform: translateX(4px); }

.link-btn {
  border: 0;
  padding: 0;
  background: none;
  color: var(--m);
  font-weight: 600;
  cursor: pointer;
  text-decoration: underline;
  text-underline-offset: 3px;
}

.tag {
  display: inline-flex;
  align-items: center;
  padding: 3px 9px;
  border-radius: 999px;
  background: var(--paper-2);
  font-size: 11.5px;
  color: var(--ink-soft);
  font-weight: 550;
}
.tag--free { background: rgba(0, 160, 223, 0.12); color: #0076a8; margin-left: 8px; }

.badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 11.5px;
  font-weight: 650;
  border: 1px solid transparent;
}
.badge--neutral { background: var(--paper-2); color: var(--muted); }
.badge--open { background: var(--green-bg); color: var(--green); }
.badge--locked { background: rgba(18, 22, 28, 0.06); color: var(--faint); }
.badge--used { background: var(--green-bg); color: var(--green); }
.badge--unused { background: rgba(0, 160, 223, 0.1); color: #0076a8; }
.badge--disabled { background: rgba(192, 57, 43, 0.1); color: var(--red); }

.form { display: grid; gap: 20px; }
.field { display: grid; gap: 8px; }
.field label { font-size: 13px; font-weight: 650; letter-spacing: 0.02em; }
.input {
  height: 54px;
  padding: 0 16px;
  background: #fff;
  border: 1px solid var(--line-strong);
  border-radius: 13px;
  font-size: 16px;
  transition: border-color 0.2s, box-shadow 0.2s;
  width: 100%;
}
.input::placeholder { color: var(--faint); }
.input:focus {
  outline: none;
  border-color: var(--ink);
  box-shadow: 0 0 0 4px rgba(0, 160, 223, 0.13);
}
.input--code {
  font-family: var(--mono);
  font-size: 19px;
  letter-spacing: 0.14em;
  text-align: center;
  text-transform: uppercase;
}
.field-hint { font-size: 12px; color: var(--faint); }
.form-error {
  margin: 0;
  padding: 12px 14px;
  border-radius: 11px;
  background: var(--red-bg);
  border: 1px solid rgba(192, 57, 43, 0.2);
  color: var(--red);
  font-size: 13.5px;
}
.form-error[hidden] { display: none; }

/* ---------- 5. 首页 ---------- */
.hero { padding: 76px 0 84px; overflow: hidden; }
.hero-inner {
  display: grid;
  grid-template-columns: 1.04fr 0.96fr;
  gap: 56px;
  align-items: center;
}
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 11.5px;
  font-weight: 650;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
}
.cmyk { display: inline-flex; gap: 3px; }
.cmyk i { width: 6px; height: 6px; border-radius: 50%; }
.cmyk i:nth-child(1) { background: var(--c); }
.cmyk i:nth-child(2) { background: var(--m); }
.cmyk i:nth-child(3) { background: var(--y); }
.cmyk i:nth-child(4) { background: var(--k); }

.hero h1 {
  margin: 22px 0 22px;
  font-size: clamp(34px, 4.6vw, 56px);
  line-height: 1.14;
  letter-spacing: -0.035em;
  font-weight: 800;
}
.hero h1 em {
  font-style: normal;
  background: linear-gradient(transparent 60%, rgba(255, 196, 0, 0.55) 60%, rgba(255, 196, 0, 0.55) 88%, transparent 88%);
  padding-bottom: 2px;
}
.hero-desc { max-width: 33em; font-size: 16px; line-height: 1.8; color: var(--muted); }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 30px 0 28px; }
.hero-proof {
  display: flex;
  flex-wrap: wrap;
  gap: 22px;
  font-size: 13px;
  color: var(--muted);
}
.hero-proof li { display: flex; align-items: center; gap: 7px; }
.hero-proof .icon { width: 16px; height: 16px; color: var(--faint); }
.hero-proof b { color: var(--ink); font-weight: 700; }

.hero-visual { position: relative; }
.sample-stack { position: relative; padding: 0 0 14px 14px; }
.sample-card {
  position: relative;
  z-index: 2;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 20px;
  padding: 20px;
  box-shadow: var(--shadow);
  transform: rotate(-1.6deg);
  animation: cardIn 1s var(--ease) both;
}
.sample-card--back {
  position: absolute;
  inset: 14px 14px 0 0;
  z-index: 1;
  transform: rotate(3deg);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(18, 22, 28, 0.06);
}
@keyframes cardIn {
  from { opacity: 0; transform: rotate(-6deg) translateY(18px); }
  to { opacity: 1; transform: rotate(-1.6deg) translateY(0); }
}
.sample-head { display: flex; align-items: center; justify-content: space-between; }
.sample-tag {
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.18em;
  color: var(--faint);
  border: 1px solid var(--line);
  padding: 3px 7px;
  border-radius: 5px;
}
.sample-brand { font-size: 12px; font-weight: 700; letter-spacing: 0.02em; }
.sample-art {
  position: relative;
  height: 132px;
  margin: 16px 0;
  border-radius: 12px;
  overflow: hidden;
  background:
    radial-gradient(circle at 18% 28%, rgba(0, 160, 223, 0.95) 0 26%, transparent 27%),
    radial-gradient(circle at 52% 66%, rgba(230, 0, 126, 0.9) 0 30%, transparent 31%),
    radial-gradient(circle at 84% 22%, rgba(255, 196, 0, 0.95) 0 24%, transparent 25%),
    linear-gradient(135deg, #15181d, #2c333d 60%, #101317);
}
.sample-art::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(rgba(255, 255, 255, 0.22) 0.7px, transparent 0.8px);
  background-size: 5px 5px;
  mix-blend-mode: overlay;
}
.sample-art span {
  position: absolute;
  border-radius: 50%;
  filter: blur(1px);
  mix-blend-mode: screen;
}
.sample-art span:nth-child(1) { width: 90px; height: 90px; left: 8%; top: 12%; background: radial-gradient(circle, rgba(0, 160, 223, 0.6), transparent 70%); }
.sample-art span:nth-child(2) { width: 110px; height: 110px; left: 38%; top: 40%; background: radial-gradient(circle, rgba(230, 0, 126, 0.55), transparent 70%); }
.sample-art span:nth-child(3) { width: 80px; height: 80px; right: 4%; top: 6%; background: radial-gradient(circle, rgba(255, 196, 0, 0.55), transparent 70%); }
.sample-art span:nth-child(4) { width: 140px; height: 140px; right: -6%; bottom: -30%; background: radial-gradient(circle, rgba(255, 255, 255, 0.16), transparent 70%); }

.sample-foot { display: flex; align-items: flex-end; justify-content: space-between; gap: 12px; }
.sample-code small { display: block; font-size: 8.5px; letter-spacing: 0.16em; color: var(--faint); margin-bottom: 5px; }
.sample-code b {
  font-family: var(--mono);
  font-size: 16px;
  letter-spacing: 0.1em;
  font-weight: 600;
}
.sample-qr {
  width: 66px;
  height: 66px;
  padding: 4px;
  border: 1px solid var(--line);
  border-radius: 9px;
  background: #fff;
  flex: none;
}
.sample-qr svg { width: 100%; height: 100%; }
.visual-note {
  margin-top: 16px;
  text-align: center;
  font-size: 12px;
  color: var(--faint);
  letter-spacing: 0.02em;
}

/* ---------- 6. 通用区块 ---------- */
.section { padding: 74px 0; }
.section--tight { padding: 30px 0; }
.section-head { max-width: 640px; margin-bottom: 40px; }
.section-head h2 {
  margin: 14px 0 12px;
  font-size: clamp(26px, 3.2vw, 36px);
  line-height: 1.25;
  letter-spacing: -0.025em;
  font-weight: 780;
}
.section-desc { color: var(--muted); font-size: 15px; }
.section-head--row {
  max-width: none;
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 20px;
}
.section-head--row h2 { margin-top: 10px; }
.h3 { font-size: 20px; font-weight: 720; letter-spacing: -0.01em; margin-bottom: 16px; }

.band { background: var(--ink); color: rgba(255, 255, 255, 0.94); }
.band-inner { display: flex; align-items: center; justify-content: space-between; gap: 24px; padding: 30px 24px; flex-wrap: wrap; }
.band-title { font-size: 16px; font-weight: 600; letter-spacing: -0.01em; }
.band-points { display: flex; gap: 22px; font-size: 12.5px; color: rgba(255, 255, 255, 0.62); }
.band-points li { position: relative; padding-left: 12px; }
.band-points li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--y);
  transform: translateY(-50%);
}

/* ---------- 7. 步骤 ---------- */
.steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  border-top: 1px solid var(--line);
}
.step {
  padding: 26px 22px 26px 0;
  border-right: 1px solid var(--line);
  padding-right: 22px;
}
.step:last-child { border-right: 0; }
.step:not(:first-child) { padding-left: 22px; }
.step-num {
  display: block;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--m);
  margin-bottom: 14px;
}
.step h3 { font-size: 16.5px; font-weight: 700; letter-spacing: -0.01em; margin-bottom: 8px; }
.step p { font-size: 13.5px; color: var(--muted); line-height: 1.7; }

/* ---------- 8. 课程卡 ---------- */
.course-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 22px;
}
.course-card {
  display: block;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 20px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: transform 0.35s var(--ease), box-shadow 0.35s, border-color 0.2s;
}
.course-card:hover { transform: translateY(-5px); box-shadow: var(--shadow); border-color: var(--line-strong); }
.course-cover {
  position: relative;
  aspect-ratio: 16 / 10;
  background: var(--paper-2);
  overflow: hidden;
}
.course-cover img { width: 100%; height: 100%; object-fit: cover; transition: transform 0.6s var(--ease); }
.course-card:hover .course-cover img { transform: scale(1.04); }
.course-level {
  position: absolute;
  top: 12px;
  left: 12px;
  padding: 4px 10px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(6px);
  font-size: 11px;
  font-weight: 650;
  letter-spacing: 0.03em;
}
.course-state {
  position: absolute;
  top: 12px;
  right: 12px;
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 650;
  background: var(--green);
  color: #fff;
}
.course-body { padding: 20px 20px 22px; }
.course-body h3 { font-size: 17.5px; font-weight: 720; line-height: 1.4; letter-spacing: -0.015em; }
.course-body p {
  margin: 8px 0 16px;
  font-size: 13px;
  color: var(--muted);
  line-height: 1.6;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.course-meta { display: flex; gap: 16px; font-size: 12px; color: var(--faint); }
.course-meta span { display: inline-flex; align-items: center; gap: 5px; }
.course-meta .icon { width: 14px; height: 14px; }

/* ---------- 9. 为什么 / FAQ / CTA ---------- */
.split { display: grid; grid-template-columns: 1.15fr 0.85fr; gap: 60px; align-items: start; }
.split h2 { font-size: clamp(26px, 3vw, 34px); letter-spacing: -0.025em; margin: 14px 0 14px; font-weight: 780; }
.lede { font-size: 16px; color: var(--muted); line-height: 1.8; margin-bottom: 28px; }
.checklist { display: grid; gap: 20px; }
.checklist li { display: flex; gap: 13px; align-items: flex-start; }
.checklist .icon { width: 20px; height: 20px; color: var(--green); margin-top: 3px; }
.checklist b { display: block; font-size: 15px; font-weight: 680; margin-bottom: 3px; }
.checklist span { font-size: 13.5px; color: var(--muted); line-height: 1.7; }
.split-side { display: grid; gap: 18px; position: sticky; top: 92px; }
.quote-card {
  background: var(--ink);
  color: #fff;
  border-radius: 20px;
  padding: 28px;
  position: relative;
  overflow: hidden;
}
.quote-card::after {
  content: "";
  position: absolute;
  right: -40px;
  top: -40px;
  width: 140px;
  height: 140px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(230, 0, 126, 0.55), transparent 70%);
}
.quote-card p { font-size: 19px; line-height: 1.6; letter-spacing: -0.01em; font-weight: 600; }
.quote-card span { display: block; margin-top: 16px; font-size: 12px; color: rgba(255, 255, 255, 0.5); }
.stat-card {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 20px 8px;
  text-align: center;
  box-shadow: var(--shadow-sm);
}
.stat-card div { border-right: 1px solid var(--line); }
.stat-card div:last-child { border-right: 0; }
.stat-card b { display: block; font-size: 26px; font-weight: 780; letter-spacing: -0.03em; }
.stat-card span { font-size: 11.5px; color: var(--faint); }

.faq { border-top: 1px solid var(--line); }
.faq details { border-bottom: 1px solid var(--line); }
.faq summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 20px 2px;
  font-size: 15.5px;
  font-weight: 650;
  cursor: pointer;
  list-style: none;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: "+";
  font-family: var(--mono);
  font-size: 18px;
  color: var(--faint);
  transition: transform 0.25s var(--ease);
}
.faq details[open] summary::after { transform: rotate(45deg); }
.faq p { padding: 0 40px 22px 2px; color: var(--muted); font-size: 14px; line-height: 1.8; max-width: 64em; }

.cta-band {
  background: var(--ink);
  color: #fff;
  position: relative;
  overflow: hidden;
  margin-top: 20px;
}
.cta-band::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(600px 200px at 12% 0%, rgba(0, 160, 223, 0.35), transparent 70%),
    radial-gradient(500px 220px at 92% 100%, rgba(230, 0, 126, 0.3), transparent 70%);
}
.cta-inner {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 52px 24px;
  flex-wrap: wrap;
}
.cta-inner h2 { font-size: clamp(24px, 3vw, 32px); letter-spacing: -0.025em; margin-bottom: 8px; }
.cta-inner p { color: rgba(255, 255, 255, 0.62); font-size: 14px; }

/* ---------- 10. 页脚 ---------- */
.site-footer { border-top: 1px solid var(--line); margin-top: 0; padding: 48px 0 40px; background: var(--paper); }
.footer-inner { display: grid; gap: 20px; }
.footer-brand { display: flex; align-items: flex-start; gap: 12px; }
.footer-brand b { font-size: 15px; }
.footer-brand p { font-size: 12.5px; color: var(--faint); margin-top: 2px; }
.footer-links { display: flex; flex-wrap: wrap; gap: 18px; font-size: 13px; color: var(--muted); }
.footer-links a:hover { color: var(--ink); }
.footer-note { font-size: 12px; color: var(--faint); }
.footer-legal {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  font-size: 11.5px;
  color: var(--faint);
}

.notice-bar {
  background: rgba(255, 196, 0, 0.16);
  border-bottom: 1px solid rgba(255, 196, 0, 0.32);
  font-size: 13px;
  color: #6b4c00;
  padding: 9px 0;
}

/* ---------- 11. 客服浮窗 ---------- */
.kefu { position: fixed; right: 20px; bottom: 22px; z-index: 60; }
.kefu-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  height: 46px;
  padding: 0 18px;
  border: 0;
  border-radius: 999px;
  background: var(--ink);
  color: #fff;
  font-size: 13.5px;
  font-weight: 600;
  box-shadow: 0 10px 28px rgba(18, 22, 28, 0.28);
  cursor: pointer;
  transition: transform 0.2s var(--ease);
}
.kefu-btn:hover { transform: translateY(-2px); }
.kefu-btn .icon { width: 18px; height: 18px; color: #4ade80; }
.kefu-panel {
  position: absolute;
  right: 0;
  bottom: 58px;
  width: 268px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 18px;
  box-shadow: var(--shadow);
}
.kefu-panel[hidden] { display: none; }
.kefu-head { display: flex; align-items: center; gap: 8px; font-size: 13px; font-weight: 650; color: var(--muted); }
.kefu-head .icon { width: 17px; height: 17px; color: var(--green); }
.kefu-id {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin: 12px 0 10px;
  padding: 11px 12px;
  border-radius: 10px;
  background: var(--paper);
  cursor: pointer;
}
.kefu-id b { font-family: var(--mono); font-size: 14px; letter-spacing: 0.02em; }
.copy-hint { display: inline-flex; align-items: center; gap: 4px; font-size: 11px; color: var(--faint); }
.copy-hint .icon { width: 13px; height: 13px; }
.kefu-tip { font-size: 12px; color: var(--faint); line-height: 1.6; }

/* ---------- 12. 兑换页 ---------- */
.redeem-page { padding: 64px 0 90px; }
.redeem-card {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 24px;
  padding: 44px 40px 36px;
  box-shadow: var(--shadow);
}
.redeem-card h1 { font-size: clamp(26px, 4vw, 34px); letter-spacing: -0.03em; margin: 16px 0 10px; font-weight: 790; }
.redeem-desc { font-size: 14px; color: var(--muted); margin-bottom: 26px; }
.inline-note {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 13px;
  margin-bottom: 20px;
  border-radius: 10px;
  background: var(--paper);
  font-size: 12.5px;
  color: var(--muted);
}
.inline-note .icon { width: 15px; height: 15px; }
.redeem-foot {
  display: grid;
  gap: 8px;
  margin-top: 24px;
  padding-top: 20px;
  border-top: 1px dashed var(--line-strong);
  font-size: 12.5px;
  color: var(--faint);
}
.redeem-foot p { display: flex; align-items: center; gap: 7px; }
.redeem-foot .icon { width: 15px; height: 15px; }
.redeem-steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 28px;
}
.redeem-steps div {
  padding: 18px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.5);
}
.redeem-steps span { font-family: var(--mono); font-size: 11px; letter-spacing: 0.1em; color: var(--m); }
.redeem-steps p { font-size: 13px; color: var(--muted); margin-top: 8px; line-height: 1.6; }

/* ---------- 13. 课程详情 ---------- */
.course-hero { padding: 26px 0 10px; }
.crumbs { display: flex; align-items: center; gap: 8px; font-size: 12px; color: var(--faint); margin-bottom: 26px; }
.crumbs .icon { width: 13px; height: 13px; }
.crumbs a:hover { color: var(--ink); }
.course-hero-grid { display: grid; grid-template-columns: 1.25fr 0.75fr; gap: 48px; align-items: center; }
.course-hero h1 { font-size: clamp(28px, 4vw, 42px); line-height: 1.2; letter-spacing: -0.035em; margin: 16px 0 12px; font-weight: 800; }
.course-sub { font-size: 15.5px; color: var(--muted); max-width: 34em; }
.tagrow { display: flex; flex-wrap: wrap; gap: 7px; margin: 18px 0 26px; }
.course-actions { display: flex; flex-wrap: wrap; gap: 12px; }
.course-hero-cover {
  aspect-ratio: 16 / 10;
  border-radius: 20px;
  overflow: hidden;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  transform: rotate(1.2deg);
  background: var(--paper-2);
}
.course-hero-cover img { width: 100%; height: 100%; object-fit: cover; }

.course-layout { display: grid; grid-template-columns: 1fr 320px; gap: 56px; align-items: start; padding-top: 26px; padding-bottom: 80px; }
.prose { font-size: 15px; line-height: 1.9; color: var(--ink-soft); }
.prose p { margin-bottom: 14px; }
.curriculum { border-top: 1px solid var(--line); }
.curriculum-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin-bottom: 14px;
}
.curriculum-head .h3 { margin-bottom: 0; }
.chapter { padding: 22px 0 6px; border-bottom: 1px solid var(--line); }
.chapter h3 {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--faint);
  margin-bottom: 10px;
}
.lesson-row { border-radius: 12px; transition: background 0.2s; }
.lesson-row:hover { background: rgba(255, 255, 255, 0.8); }
.lesson-row.is-locked { opacity: 0.6; }
.lesson-link {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 12px 12px;
}
.lesson-index { font-family: var(--mono); font-size: 11.5px; color: var(--faint); width: 22px; }
.lesson-title { flex: 1; font-size: 14.5px; font-weight: 550; line-height: 1.5; }
.lesson-time { font-size: 11.5px; color: var(--faint); font-variant-numeric: tabular-nums; }
.lesson-lock { color: var(--faint); display: flex; }
.lesson-lock .icon { width: 16px; height: 16px; }

.side-card {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 22px;
  box-shadow: var(--shadow-sm);
}
.course-side { position: sticky; top: 92px; }
.side-state { margin-bottom: 18px; }
.side-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  border-radius: 999px;
  background: var(--paper);
  font-size: 12.5px;
  font-weight: 650;
  color: var(--muted);
}
.side-badge.is-open { background: var(--green-bg); color: var(--green); }
.side-badge .icon { width: 15px; height: 15px; }
.side-state p { font-size: 12.5px; color: var(--faint); margin-top: 10px; line-height: 1.6; }
.side-list { display: grid; gap: 9px; margin-top: 18px; font-size: 12.5px; color: var(--muted); }
.side-list li { display: flex; align-items: center; gap: 8px; }
.side-list .icon { width: 14px; height: 14px; color: var(--green); }

.sticky-cta { display: none; }

/* ---------- 14. 学习页 ---------- */
.learn-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding-top: 22px;
  padding-bottom: 18px;
}
.back-link { display: inline-flex; align-items: center; gap: 8px; font-size: 13px; color: var(--muted); }
.back-link:hover { color: var(--ink); }
.back-link .icon { width: 17px; height: 17px; }
.learn-progress { display: flex; align-items: center; gap: 12px; font-size: 12px; color: var(--faint); font-variant-numeric: tabular-nums; }
.bar { width: 160px; height: 4px; border-radius: 999px; background: rgba(18, 22, 28, 0.08); overflow: hidden; }
.bar i { display: block; height: 100%; background: linear-gradient(90deg, var(--c), var(--m)); border-radius: 999px; transition: width 0.4s var(--ease); }
.bar--sm { width: 100%; height: 3px; margin: 8px 0 6px; }

.learn-layout { display: grid; grid-template-columns: 1fr 320px; gap: 40px; align-items: start; padding-bottom: 80px; }
.stage {
  border-radius: 18px;
  overflow: hidden;
  background: #0b0d10;
  box-shadow: 0 20px 50px rgba(18, 22, 28, 0.18);
  aspect-ratio: 16 / 9;
}
.player { width: 100%; height: 100%; object-fit: contain; background: #000; }
.video-empty {
  height: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  align-items: center;
  gap: 24px;
  padding: 32px;
  color: #fff;
  background:
    radial-gradient(500px 220px at 10% 10%, rgba(0, 160, 223, 0.35), transparent 70%),
    radial-gradient(400px 240px at 90% 90%, rgba(230, 0, 126, 0.32), transparent 70%),
    linear-gradient(135deg, #14171c, #1d232b);
}
.video-empty-art { position: relative; height: 100%; min-height: 150px; }
.video-empty-art span { position: absolute; border-radius: 50%; filter: blur(2px); mix-blend-mode: screen; }
.video-empty-art span:nth-child(1) { width: 110px; height: 110px; left: 8%; top: 10%; background: radial-gradient(circle, rgba(0, 160, 223, 0.65), transparent 70%); }
.video-empty-art span:nth-child(2) { width: 130px; height: 130px; left: 30%; top: 40%; background: radial-gradient(circle, rgba(230, 0, 126, 0.6), transparent 70%); }
.video-empty-art span:nth-child(3) { width: 90px; height: 90px; right: 6%; top: 8%; background: radial-gradient(circle, rgba(255, 196, 0, 0.6), transparent 70%); }
.video-empty-art span:nth-child(4) { width: 160px; height: 160px; right: -4%; bottom: -20%; background: radial-gradient(circle, rgba(255, 255, 255, 0.14), transparent 70%); }
.video-empty-text .eyebrow { color: rgba(255, 255, 255, 0.4); }
.video-empty-text h2 { font-size: clamp(20px, 2.4vw, 26px); margin: 12px 0 8px; letter-spacing: -0.02em; }
.video-empty-text p { font-size: 13px; color: rgba(255, 255, 255, 0.55); line-height: 1.7; max-width: 26em; }
.learn-title { padding: 26px 2px 4px; }
.learn-title h1 { font-size: clamp(22px, 2.8vw, 30px); letter-spacing: -0.025em; margin-top: 10px; line-height: 1.35; }
.learn-meta { display: flex; flex-wrap: wrap; gap: 16px; margin-top: 12px; font-size: 12.5px; color: var(--faint); }
.learn-meta span { display: inline-flex; align-items: center; gap: 6px; }
.learn-meta .icon { width: 14px; height: 14px; }
.done-flag { color: var(--green); }
.lesson-note {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  margin-top: 26px;
  padding: 16px 18px;
  border-radius: 14px;
  background: rgba(0, 160, 223, 0.07);
  border: 1px solid rgba(0, 160, 223, 0.16);
}
.lesson-note .icon { width: 18px; height: 18px; color: var(--c); margin-top: 2px; }
.lesson-note p { font-size: 13px; color: #2c6b8a; line-height: 1.7; }
.lesson-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 34px; }
.lesson-prev, .lesson-next {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  transition: border-color 0.2s, transform 0.2s var(--ease);
}
.lesson-prev:hover, .lesson-next:hover { border-color: var(--line-strong); transform: translateY(-2px); }
.lesson-next { justify-content: flex-end; text-align: right; }
.lesson-prev .icon, .lesson-next .icon { width: 18px; height: 18px; color: var(--faint); }
.lesson-prev small, .lesson-next small { display: block; font-size: 11px; color: var(--faint); }
.lesson-prev b, .lesson-next b { display: block; font-size: 13.5px; font-weight: 600; line-height: 1.4; }
.learn-side { position: sticky; top: 90px; }
.side-card--list { padding: 0; overflow: hidden; }
.side-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 18px;
  border-bottom: 1px solid var(--line);
  font-size: 13px;
}
.side-head span { font-size: 11.5px; color: var(--faint); font-variant-numeric: tabular-nums; }
.side-lessons { max-height: 62vh; overflow-y: auto; }
.side-lessons li { border-bottom: 1px solid rgba(18, 22, 28, 0.05); }
.side-lessons li:last-child { border-bottom: 0; }
.side-lessons a { display: flex; align-items: center; gap: 10px; padding: 11px 18px; font-size: 13px; color: var(--muted); }
.side-lessons a:hover { background: var(--paper); color: var(--ink); }
.side-lessons .n { font-family: var(--mono); font-size: 10.5px; color: var(--faint); }
.side-lessons .t { flex: 1; line-height: 1.45; }
.side-lessons .d { font-size: 10.5px; color: var(--faint); }
.side-lessons li.is-current { background: var(--paper); }
.side-lessons li.is-current a { color: var(--ink); font-weight: 620; }
.side-lessons li.is-current { box-shadow: inset 3px 0 0 var(--m); }

/* ---------- 15. 我的 ---------- */
.me-page { padding-top: 46px; padding-bottom: 90px; }
.me-head { display: flex; align-items: flex-end; justify-content: space-between; gap: 20px; margin-bottom: 30px; }
.me-head h1 { font-size: clamp(28px, 4vw, 38px); letter-spacing: -0.03em; margin: 12px 0 6px; }
.me-sub { font-size: 13.5px; color: var(--muted); }
.success-banner {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 16px 18px;
  margin-bottom: 28px;
  border-radius: 14px;
  background: var(--green-bg);
  border: 1px solid rgba(15, 138, 95, 0.2);
}
.success-banner .icon { width: 20px; height: 20px; color: var(--green); margin-top: 2px; }
.success-banner b { display: block; font-size: 14px; color: var(--green); }
.success-banner span { font-size: 12.5px; color: #3c6a58; }
.me-grid { display: grid; grid-template-columns: 1fr 330px; gap: 48px; align-items: start; }
.me-courses { display: grid; gap: 12px; }
.me-course {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 14px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 16px;
  transition: border-color 0.2s, transform 0.2s var(--ease);
}
.me-course:hover { border-color: var(--line-strong); transform: translateY(-2px); }
.me-course-cover { width: 88px; height: 66px; border-radius: 10px; overflow: hidden; background: var(--paper-2); flex: none; }
.me-course-cover img { width: 100%; height: 100%; object-fit: cover; }
.me-course-body { flex: 1; min-width: 0; }
.me-course-body b { font-size: 14.5px; font-weight: 650; display: block; text-wrap: balance; }
.me-course-body span { font-size: 11.5px; color: var(--faint); }
.me-course-body em { font-style: normal; font-size: 11px; color: var(--faint); }
.me-course > .icon { color: var(--faint); width: 18px; height: 18px; }
.me-side { display: grid; gap: 16px; position: sticky; top: 92px; }
.side-title { font-size: 13px; font-weight: 700; display: block; margin-bottom: 14px; }
.grant-list { display: grid; gap: 12px; }
.grant-list li { display: flex; align-items: center; justify-content: space-between; gap: 10px; font-size: 12.5px; }
.grant-scope { font-weight: 600; }
.grant-exp { color: var(--faint); font-size: 11.5px; }
.is-expired { color: var(--red); font-style: normal; }
.grant-empty { color: var(--faint); font-size: 12.5px; }
.history-list { display: grid; gap: 12px; }
.history-list li { display: grid; gap: 2px; }
.history-list b { font-family: var(--mono); font-size: 12.5px; letter-spacing: 0.06em; }
.history-list span { font-size: 11.5px; color: var(--faint); }
.side-card--help p { font-size: 12.5px; color: var(--muted); margin-bottom: 14px; line-height: 1.6; }
.empty-state {
  padding: 34px;
  border: 1px dashed var(--line-strong);
  border-radius: 16px;
  text-align: center;
  background: rgba(255, 255, 255, 0.5);
}
.empty-state p { font-size: 15px; font-weight: 650; }
.empty-state span { display: block; font-size: 12.5px; color: var(--faint); margin: 8px 0 18px; }
.mini-course-list { display: grid; border-top: 1px solid var(--line); }
.mini-course {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 15px 2px;
  border-bottom: 1px solid var(--line);
  font-size: 14px;
}
.mini-course:hover { color: var(--m); }

/* ---------- 16. 协议 / 404 ---------- */
.legal-page { padding-top: 56px; padding-bottom: 90px; }
.legal-page h1 { font-size: clamp(28px, 4vw, 38px); letter-spacing: -0.03em; margin: 14px 0 8px; }
.legal-meta { font-size: 12px; color: var(--faint); margin-bottom: 34px; }
.legal-prose h2 { font-size: 16px; font-weight: 700; margin: 28px 0 10px; letter-spacing: -0.01em; }
.legal-prose p { font-size: 14px; line-height: 1.9; color: var(--ink-soft); }
.legal-back { margin-top: 40px; }
.legal-back a { display: inline-flex; align-items: center; gap: 8px; font-size: 13px; color: var(--muted); }
.notfound { padding: 110px 0 130px; text-align: center; }
.notfound h1 { font-size: clamp(28px, 4vw, 40px); letter-spacing: -0.03em; margin: 14px 0 10px; }
.notfound > p { color: var(--muted); font-size: 14px; }
.notfound-actions { display: flex; gap: 12px; justify-content: center; margin-top: 28px; flex-wrap: wrap; }

/* ---------- 17. 响应式 ---------- */
@media (max-width: 1024px) {
  .hero-inner { grid-template-columns: 1fr; gap: 48px; }
  .hero-visual { max-width: 460px; }
  .course-layout { grid-template-columns: 1fr 280px; gap: 36px; }
  .learn-layout { grid-template-columns: 1fr 280px; gap: 28px; }
  .me-grid { grid-template-columns: 1fr 280px; gap: 32px; }
  .split { gap: 36px; }
}

@media (max-width: 860px) {
  .steps { grid-template-columns: repeat(2, 1fr); }
  .step:nth-child(2) { border-right: 0; }
  .step:nth-child(3), .step:nth-child(4) { border-top: 1px solid var(--line); }
  .course-grid { grid-template-columns: repeat(2, 1fr); }
  .course-hero-grid { grid-template-columns: 1fr; gap: 28px; }
  .course-hero-cover { max-width: 420px; transform: none; }
  .course-layout, .learn-layout, .me-grid, .split { grid-template-columns: 1fr; }
  .course-side, .learn-side, .me-side, .split-side { position: static; }
  .reach-side { position: static; }
  .learn-side { order: -1; }
  .side-lessons { max-height: 240px; }
  .band-inner { flex-direction: column; align-items: flex-start; gap: 12px; }
  .nav-link { padding: 8px 9px; font-size: 13px; }
  .header-inner { gap: 14px; }
}

@media (max-width: 640px) {
  body { font-size: 14.5px; }
  .shell { padding: 0 18px; }
  .header-inner { height: 60px; gap: 10px; }
  .brand-text em { display: none; }
  .brand-text b { font-size: 15px; }
  .nav { gap: 0; }
  .nav-link { padding: 8px 6px; font-size: 12.5px; }
  .nav-link.is-active::after { display: none; }
  .header-cta { display: none; }
  .hero { padding: 44px 0 56px; }
  .hero h1 { margin: 16px 0 16px; }
  .hero-desc { font-size: 14.5px; }
  .hero-actions .btn { flex: 1 1 100%; }
  .hero-proof { gap: 12px 18px; font-size: 12px; }
  .sample-card { padding: 16px; }
  .sample-art { height: 110px; margin: 12px 0; }
  .sample-code b { font-size: 14px; }
  .sample-qr { width: 56px; height: 56px; }
  .section { padding: 52px 0; }
  .steps { grid-template-columns: 1fr; border-top: 0; }
  .step { border-right: 0; border-top: 1px solid var(--line); padding: 20px 0; }
  .step:not(:first-child) { padding-left: 0; }
  .course-grid { grid-template-columns: 1fr; gap: 16px; }
  .course-body { padding: 16px 16px 18px; }
  .section-head { margin-bottom: 28px; }
  .section-head--row { flex-direction: column; align-items: flex-start; gap: 10px; }
  .band-points { flex-wrap: wrap; gap: 8px 18px; }
  .cta-inner { padding: 40px 18px; }
  .cta-inner .btn { width: 100%; }
  .redeem-card { padding: 28px 20px 24px; border-radius: 20px; }
  .redeem-steps { grid-template-columns: 1fr; gap: 10px; }
  .redeem-page { padding: 34px 0 70px; }
  .course-layout { padding-bottom: 40px; }
  .sticky-cta {
    display: flex;
    position: fixed;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 50;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    padding: 12px 16px calc(12px + env(safe-area-inset-bottom));
    background: rgba(255, 255, 255, 0.94);
    backdrop-filter: blur(12px);
    border-top: 1px solid var(--line);
  }
  .sticky-cta b { display: block; font-size: 13.5px; }
  .sticky-cta span { font-size: 11px; color: var(--faint); }
  .sticky-cta .btn { height: 44px; padding: 0 18px; font-size: 14px; border-radius: 12px; }
  .page--course { padding-bottom: 76px; }
  .page--redeem, .page--me, .page--learn { padding-bottom: 72px; }
  .video-empty { grid-template-columns: 1fr; gap: 10px; padding: 22px; }
  .video-empty-art { display: none; }
  .stage { aspect-ratio: 16 / 10; border-radius: 14px; }
  .learn-head { padding-top: 14px; }
  .learn-progress .bar { width: 90px; }
  .lesson-nav { grid-template-columns: 1fr; }
  .learn-side { order: 0; }
  .me-head { flex-direction: row; align-items: flex-start; gap: 12px; }
  .me-head h1 { font-size: 26px; margin: 8px 0 4px; }
  .logout-form { flex: none; padding-top: 2px; }
  .logout-form .btn { height: 34px; padding: 0 11px; font-size: 12px; }
  .me-course { gap: 12px; padding: 12px; }
  .me-course-cover { width: 64px; height: 50px; border-radius: 8px; }
  .me-course-body b { font-size: 13.5px; }
  .kefu { right: 14px; bottom: 16px; }
  .kefu-panel { width: 246px; }
  .footer-links { gap: 12px; font-size: 12px; }
  .sticky-cta ~ .kefu { bottom: 80px; }
  .page--course .kefu { bottom: 82px; }
  .faq p { padding-right: 12px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ---------- 18. 轻提示 ---------- */
.toast {
  position: fixed;
  left: 50%;
  bottom: 88px;
  transform: translate(-50%, 12px);
  z-index: 200;
  max-width: 82vw;
  padding: 11px 18px;
  border-radius: 999px;
  background: rgba(18, 22, 28, 0.92);
  color: #fff;
  font-size: 13px;
  box-shadow: 0 12px 30px rgba(18, 22, 28, 0.25);
  opacity: 0;
  transition: opacity 0.2s, transform 0.2s var(--ease);
  pointer-events: none;
}
.toast.is-in { opacity: 1; transform: translate(-50%, 0); }

/* ---------- 19. 打印（兑换卡） ---------- */
@media print {
  body { background: #fff; }
  body::before { display: none; }
  .site-header, .site-footer, .kefu, .sticky-cta, .print-toolbar, .skip-link, .notice-bar { display: none !important; }
  .print-sheet { display: grid; grid-template-columns: 1fr 1fr; gap: 10mm; }
  .print-card { break-inside: avoid; border: 1px solid #bbb; }
}