:root {
  color-scheme: light;
  --bg: #f6f7f9;
  --paper: #ffffff;
  --ink: #18222d;
  --muted: #65727f;
  --line: #d7e0e6;
  --soft: #eef4f6;
  --shadow: 0 12px 26px rgba(24, 34, 45, 0.07);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Microsoft YaHei", "PingFang SC", "Noto Sans SC", Arial, sans-serif;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  min-height: 58px;
  padding: 10px clamp(14px, 4vw, 42px);
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(14px);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

.brand span {
  display: grid;
  width: 44px;
  height: 36px;
  place-items: center;
  border-radius: 8px;
  background: #132a38;
  color: #fff;
  font-weight: 800;
}

.brand strong {
  font-size: 16px;
}

main {
  width: min(980px, calc(100% - 28px));
  margin: 0 auto;
  padding: 20px 0 56px;
}

.hero {
  padding: clamp(18px, 4vw, 34px);
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--paper);
  box-shadow: var(--shadow);
}

.eyebrow {
  margin: 0 0 8px;
  color: #0c8b7c;
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2,
p {
  margin-top: 0;
}

h1 {
  max-width: 840px;
  margin-bottom: 12px;
  font-size: clamp(28px, 5vw, 44px);
  line-height: 1.12;
  letter-spacing: 0;
}

.hero p:last-of-type {
  max-width: 850px;
  color: var(--muted);
  font-size: 16px;
  line-height: 1.7;
}

.hero-metrics {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  margin-top: 18px;
}

.metric {
  min-height: 72px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fbfcfd;
}

.metric strong,
.metric span {
  display: block;
}

.metric strong {
  font-size: 26px;
  line-height: 1;
}

.metric span {
  margin-top: 7px;
  color: var(--muted);
  font-size: 13px;
}

.timeline {
  position: relative;
  margin-top: 24px;
  --rail-gap: 24px;
  --rail-width: 4px;
}

.timeline-svg {
  position: absolute;
  inset: 0;
  z-index: 0;
  width: 100%;
  pointer-events: none;
  overflow: visible;
}

.timeline-lines path {
  fill: none;
  stroke-linecap: round;
  stroke-linejoin: round;
  stroke-width: var(--rail-width);
}

.timeline-dots text {
  fill: #fff;
  font-size: 10px;
  font-weight: 800;
  pointer-events: none;
}

.track-stage {
  position: relative;
  z-index: 1;
  margin: 0 var(--rail-gap);
  margin-bottom: 64px;
  padding: 18px 20px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.82);
  box-shadow: var(--shadow);
}

.track-stage:last-child {
  margin-bottom: 0;
}

.track-stage.left {
  margin-right: var(--rail-gap);
}

.track-stage.right {
  margin-left: var(--rail-gap);
}

.stage-head {
  margin-bottom: 10px;
}

.stage-head span {
  display: inline-flex;
  min-height: 28px;
  align-items: center;
  padding: 4px 9px;
  border-radius: 8px;
  background: var(--stage-soft);
  color: var(--stage-color);
  font-size: 13px;
  font-weight: 800;
}

.stage-head h2 {
  margin: 8px 0 4px;
  font-size: clamp(24px, 4vw, 34px);
}

.stage-head p {
  margin-bottom: 0;
  color: var(--muted);
  line-height: 1.6;
}

.lesson-lines {
  display: grid;
  gap: 6px;
}

.lesson-line {
  display: grid;
  grid-template-columns: 42px minmax(90px, 150px) minmax(0, 1fr) 92px 92px 72px;
  align-items: center;
  gap: 8px;
  min-height: 34px;
  padding: 5px 8px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--paper);
  box-shadow: 0 4px 12px rgba(24, 34, 45, 0.04);
}

.lesson-no {
  display: inline-grid;
  width: 30px;
  height: 24px;
  place-items: center;
  border-radius: 7px;
  background: var(--stage-color);
  color: #fff;
  font-size: 12px;
  font-weight: 800;
}

.lesson-line strong,
.lesson-line em,
.lesson-line small {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.lesson-line strong {
  font-size: 14px;
}

.lesson-line em {
  color: var(--muted);
  font-size: 13px;
  font-style: normal;
}

.difficulty-tag {
  justify-self: start;
  padding: 4px 7px;
  border-radius: 7px;
  background: var(--tail-soft);
  color: var(--tail-color);
  font-weight: 800;
}

.gesp-tag {
  justify-self: start;
  padding: 4px 7px;
  border-radius: 7px;
  background: #eef4f8;
  color: #405261;
  font-weight: 800;
}

.lesson-count {
  color: #87929c;
  font-size: 12px;
}

.stage-foot {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}

.stage-foot span {
  display: inline-flex;
  min-height: 28px;
  align-items: center;
  padding: 4px 8px;
  border-radius: 8px;
  background: var(--stage-soft);
  color: #36424d;
  font-size: 12px;
}

@media (max-width: 760px) {
  main {
    width: min(100% - 18px, 1080px);
    padding-top: 14px;
  }

  .hero {
    padding: 16px;
  }

  h1 {
    font-size: 29px;
  }

  .hero p:last-of-type {
    font-size: 15px;
  }

  .hero-metrics {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .track-stage.right,
  .track-stage.left {
    margin-right: 0;
    margin-left: 18px;
    margin-bottom: 34px;
    padding-right: 12px;
    padding-left: 16px;
  }

  .lesson-line {
    grid-template-columns: 34px minmax(78px, 120px) minmax(0, 1fr) 62px;
  }

  .difficulty-tag,
  .gesp-tag {
    display: none;
  }

  .track-stage:last-child {
    margin-bottom: 0;
  }
}