:root {
  color-scheme: light;
  --ink: #203848;
  --muted: #6c8190;
  --line: #d9eeee;
  --paper: #ffffff;
  --mint: #e7fbf7;
  --mint-strong: #2c9f92;
  --coral: #ff7b73;
  --pink: #ffdce8;
  --yellow: #ffda68;
  --blue: #77bdff;
  --lilac: #cabdff;
  --page: #eefafa;
  --shadow: 0 18px 50px rgba(29, 73, 86, 0.12);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family:
    "Microsoft YaHei",
    "PingFang SC",
    "Noto Sans CJK SC",
    Arial,
    sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at 8% 2%, rgba(255, 218, 104, 0.35), transparent 28rem),
    linear-gradient(135deg, #e7fbf7 0%, #f8fffd 46%, #fff7fb 100%);
}

.trial-bar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  min-height: 2.5rem;
  padding: 0.45rem 1rem;
  background: #203848;
  color: #ffffff;
  font-weight: 800;
}

.trial-bar b {
  color: var(--yellow);
}

.trial-expired {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: grid;
  place-items: center;
  padding: 1.2rem;
  background: rgba(238, 250, 250, 0.96);
  backdrop-filter: blur(12px);
}

.trial-expired[hidden] {
  display: none;
}

.trial-expired-card {
  display: grid;
  justify-items: center;
  gap: 0.9rem;
  width: min(32rem, 100%);
  padding: 2rem;
  border: 1px solid rgba(107, 151, 157, 0.2);
  border-radius: 1.4rem;
  background: #ffffff;
  box-shadow: var(--shadow);
  text-align: center;
}

.trial-expired-card p,
.trial-expired-card small {
  margin: 0;
  color: var(--muted);
  line-height: 1.7;
}

button,
input {
  font: inherit;
}

button {
  color: inherit;
}

a {
  color: inherit;
  text-decoration: none;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin: 1rem clamp(1rem, 3vw, 3rem);
  padding: 1rem 1.2rem;
  border: 1px solid rgba(255, 255, 255, 0.8);
  border-radius: 1.4rem;
  background: rgba(255, 255, 255, 0.9);
  box-shadow: var(--shadow);
  backdrop-filter: blur(16px);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.8rem;
}

.brand-mark {
  display: grid;
  width: 3.3rem;
  height: 3.3rem;
  place-items: center;
  border: 4px solid #ffffff;
  border-radius: 1rem;
  background: linear-gradient(135deg, var(--coral), #ffa664);
  color: #ffffff;
  font-size: 1.7rem;
  font-weight: 900;
  box-shadow: 0 12px 24px rgba(255, 123, 115, 0.26);
}

.brand strong,
.brand small {
  display: block;
  line-height: 1.25;
}

.brand strong {
  font-size: 1.35rem;
}

.brand small {
  color: var(--muted);
}

.header-stats {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 0.65rem;
}

.header-stats span {
  min-height: 2.6rem;
  padding: 0.62rem 0.85rem;
  border-radius: 0.9rem;
  background: var(--mint);
  color: #35736f;
  font-weight: 800;
}

main {
  width: min(118rem, 100%);
  margin: 0 auto;
  padding: 0 clamp(1rem, 3vw, 3rem) 3rem;
}

.hero-panel {
  display: grid;
  grid-template-columns: minmax(0, 0.95fr) minmax(18rem, 0.85fr);
  align-items: center;
  gap: 2rem;
  margin-top: 1.4rem;
  padding: clamp(1.1rem, 3vw, 2rem);
  border-radius: 1.6rem;
  background: rgba(255, 255, 255, 0.76);
  box-shadow: var(--shadow);
}

.hero-copy {
  max-width: 45rem;
}

.eyebrow {
  margin: 0 0 0.55rem;
  color: var(--mint-strong);
  font-size: 0.92rem;
  font-weight: 900;
}

h1,
h2,
h3,
p {
  overflow-wrap: anywhere;
}

h1 {
  margin: 0;
  max-width: 15ch;
  font-size: clamp(2.1rem, 4vw, 4.6rem);
  line-height: 1.06;
  letter-spacing: 0;
}

h2,
h3 {
  margin: 0;
  line-height: 1.22;
  letter-spacing: 0;
}

.hero-copy p:last-child {
  margin: 1rem 0 0;
  color: var(--muted);
  font-size: 1.08rem;
  line-height: 1.8;
}

.hero-panel img {
  display: block;
  width: 100%;
  aspect-ratio: 4 / 3;
  border-radius: 1.2rem;
  object-fit: cover;
}

.route-section,
.study-app {
  margin-top: 1.4rem;
}

.section-title {
  margin-bottom: 1rem;
}

.route-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1rem;
}

.route-grid article,
.lesson-note,
.challenge-card,
.tip-box,
.mini-cards article,
.quiz-card,
.report-grid article,
.report-card,
.mistake-card,
.empty-state {
  border: 1px solid rgba(107, 151, 157, 0.14);
  border-radius: 1rem;
  background: rgba(255, 255, 255, 0.86);
  box-shadow: 0 12px 32px rgba(29, 73, 86, 0.08);
}

.route-grid article {
  min-height: 10rem;
  padding: 1rem;
}

.route-grid span {
  display: grid;
  width: 2.2rem;
  height: 2.2rem;
  margin-bottom: 0.8rem;
  place-items: center;
  border-radius: 0.7rem;
  background: var(--yellow);
  font-weight: 900;
}

.route-grid p,
.lesson-note p,
.challenge-card p,
.tip-box p,
.mini-cards p,
.report-card p,
.mistake-card p,
.mistake-card small,
.lesson-item small,
#lessonSubtitle {
  color: var(--muted);
  line-height: 1.68;
}

.study-app {
  display: grid;
  grid-template-columns: minmax(17rem, 23rem) minmax(0, 1fr);
  gap: 1.2rem;
  align-items: start;
}

.sidebar,
.workspace {
  border-radius: 1.5rem;
  background: rgba(255, 255, 255, 0.74);
  box-shadow: var(--shadow);
}

.sidebar {
  position: sticky;
  top: 6.8rem;
  max-height: calc(100vh - 8rem);
  overflow: hidden;
  padding: 1rem;
}

.sidebar-head input {
  width: 100%;
  min-height: 3rem;
  margin-top: 1rem;
  padding: 0.7rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: 0.9rem;
  background: #f9ffff;
  outline: none;
}

.sidebar-head input:focus {
  border-color: var(--mint-strong);
  box-shadow: 0 0 0 4px rgba(44, 159, 146, 0.12);
}

.term-switch,
.feature-tabs {
  display: flex;
  gap: 0.5rem;
  padding: 0.45rem;
  border-radius: 1rem;
  background: #eaf8f8;
}

.term-switch {
  margin: 0.9rem 0;
}

.term-btn,
.feature-tab,
.back-home,
.soft-btn,
.primary-btn {
  min-height: 2.75rem;
  border: 0;
  border-radius: 0.8rem;
  cursor: pointer;
  font-weight: 900;
}

.term-btn,
.feature-tab {
  flex: 1;
  padding: 0.55rem 0.7rem;
  background: transparent;
  color: #5b7885;
}

.term-btn.is-active,
.feature-tab.is-active {
  background: #ffffff;
  color: var(--coral);
  box-shadow: 0 8px 20px rgba(29, 73, 86, 0.08);
}

.lesson-list {
  display: grid;
  gap: 0.7rem;
  max-height: calc(100vh - 22rem);
  overflow: auto;
  padding-right: 0.25rem;
}

.lesson-item {
  display: grid;
  grid-template-columns: 1.6rem minmax(0, 1fr);
  gap: 0.7rem;
  width: 100%;
  min-height: 4.9rem;
  padding: 0.85rem;
  border: 1px solid transparent;
  border-radius: 1rem;
  background: #ffffff;
  cursor: pointer;
  text-align: left;
}

.lesson-item.is-active {
  border-color: #ffc3d7;
  background: #fff2f7;
}

.lesson-item strong,
.lesson-item small {
  display: block;
}

.check-dot {
  display: grid;
  width: 1.4rem;
  height: 1.4rem;
  place-items: center;
  border: 2px solid #b9c9cf;
  border-radius: 0.35rem;
  color: var(--mint-strong);
  font-weight: 900;
}

.workspace {
  padding: clamp(1rem, 2.4vw, 1.6rem);
}

.lesson-top {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 1rem;
  align-items: center;
}

.back-home,
.soft-btn {
  padding: 0.55rem 0.85rem;
  background: var(--mint);
  color: #2e756f;
}

.danger {
  background: var(--pink);
  color: #a9416b;
}

.feature-tabs {
  margin: 1.1rem 0;
  width: min(36rem, 100%);
}

.view-panel {
  display: none;
}

.view-panel.is-active {
  display: block;
}

.lesson-note,
.challenge-card,
.tip-box {
  padding: 1rem;
  background: #fffaf0;
}

.lesson-note {
  margin-bottom: 1rem;
}

.challenge-card {
  display: grid;
  gap: 1rem;
  background: rgba(255, 255, 255, 0.88);
}

.challenge-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
}

.stars {
  color: #d79a00;
  font-size: 2rem;
  font-weight: 900;
  letter-spacing: 0;
}

.mini-cards,
.report-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.mini-cards article {
  min-height: 7rem;
  padding: 1rem;
}

.practice-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1rem;
}

.quiz-list {
  display: grid;
  gap: 1rem;
}

.quiz-card {
  padding: 1rem;
}

.question-line {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.8rem;
}

.question-line span {
  flex: 0 0 auto;
  padding: 0.35rem 0.55rem;
  border-radius: 999px;
  background: var(--mint);
  color: #33756f;
  font-size: 0.82rem;
  font-weight: 900;
}

.choice-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
}

.choice-btn {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  min-height: 3.2rem;
  padding: 0.7rem;
  border: 1px solid var(--line);
  border-radius: 0.9rem;
  background: #fbffff;
  cursor: pointer;
  text-align: left;
  font-weight: 800;
}

.choice-btn span {
  display: grid;
  width: 1.8rem;
  height: 1.8rem;
  place-items: center;
  border-radius: 50%;
  background: #edf8ff;
  color: #326f9c;
}

.choice-btn.is-selected {
  border-color: var(--coral);
  background: #fff4f3;
}

.feedback {
  min-height: 1.6rem;
  margin: 0.8rem 0 0;
  font-weight: 800;
}

.feedback.right {
  color: #238269;
}

.feedback.wrong {
  color: #b94b3d;
}

.result-box {
  min-height: 3rem;
  margin: 1rem 0;
  padding: 0.8rem;
  border-radius: 0.9rem;
  background: #f2fbff;
  color: #365366;
  font-weight: 800;
}

.primary-btn {
  width: fit-content;
  padding: 0.7rem 1.1rem;
  background: var(--ink);
  color: #ffffff;
}

.report-grid article {
  min-height: 7.5rem;
  padding: 1rem;
}

.report-grid span {
  display: block;
  color: var(--coral);
  font-size: 2.4rem;
  font-weight: 900;
  line-height: 1;
}

.report-card {
  margin-top: 1rem;
  padding: 1rem;
}

.mistake-list {
  display: grid;
  gap: 1rem;
}

.mistake-card,
.empty-state {
  padding: 1rem;
}

.mistake-card div {
  margin: 0.65rem 0;
  color: #238269;
  font-weight: 900;
}

.site-footer {
  padding: 2rem 1rem 3rem;
  color: var(--muted);
  text-align: center;
}

@media (max-width: 1050px) {
  .hero-panel,
  .study-app,
  .lesson-note,
  .challenge-card {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    max-height: none;
  }

  .lesson-list {
    max-height: 22rem;
  }

  .route-grid,
  .mini-cards,
  .report-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .app-header {
    align-items: flex-start;
    flex-direction: column;
    margin: 0.65rem;
    border-radius: 1rem;
  }

  .header-stats {
    justify-content: flex-start;
  }

  main {
    padding: 0 0.65rem 2rem;
  }

  .hero-panel {
    padding: 1rem;
  }

  h1 {
    max-width: none;
    font-size: 2.35rem;
  }

  .route-grid,
  .mini-cards,
  .report-grid,
  .choice-grid {
    grid-template-columns: 1fr;
  }

  .lesson-top,
  .practice-head {
    align-items: stretch;
    grid-template-columns: 1fr;
    flex-direction: column;
  }

  .feature-tabs {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .primary-btn,
  .soft-btn,
  .back-home {
    width: 100%;
  }

  .challenge-actions {
    flex-direction: column;
  }
}