:root {
  color-scheme: light;
  --bg: #f6f7f8;
  --panel: #ffffff;
  --ink: #202124;
  --muted: #687078;
  --line: #dde1e5;
  --teal: #0f766e;
  --teal-soft: #d8f3ee;
  --coral: #d84a2f;
  --amber: #b7791f;
  --shadow: 0 18px 42px rgba(30, 38, 47, 0.1);
}

* {
  box-sizing: border-box;
}

html {
  min-width: 320px;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--ink);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    "PingFang SC", "Microsoft YaHei", sans-serif;
}

button,
input,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-shell {
  min-height: 100vh;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 18px clamp(16px, 4vw, 44px);
  background: rgba(246, 247, 248, 0.92);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(14px);
}

.eyebrow {
  margin: 0 0 4px;
  color: var(--teal);
  font-size: 13px;
  font-weight: 700;
}

h1,
h2,
p {
  margin: 0;
}

h1 {
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1.12;
  letter-spacing: 0;
}

.topbar-stats {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
  color: var(--muted);
  font-size: 14px;
}

.topbar-stats span {
  min-height: 32px;
  display: inline-flex;
  align-items: center;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--panel);
}

.layout {
  display: grid;
  grid-template-columns: minmax(280px, 340px) minmax(0, 1fr);
  gap: 20px;
  width: min(1440px, 100%);
  margin: 0 auto;
  padding: 22px clamp(16px, 4vw, 44px) 42px;
}

.sidebar {
  align-self: start;
  position: sticky;
  top: 96px;
  display: grid;
  gap: 14px;
}

.source-panel,
.field,
.question-card,
.flash-card,
.empty-state {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  box-shadow: var(--shadow);
}

.source-panel {
  display: grid;
  grid-template-columns: 74px minmax(0, 1fr);
  gap: 12px;
  align-items: center;
  padding: 12px;
}

.source-panel img {
  width: 74px;
  height: 104px;
  object-fit: cover;
  object-position: top;
  border: 1px solid var(--line);
  border-radius: 6px;
}

.source-panel strong {
  display: block;
  margin-bottom: 6px;
  line-height: 1.35;
}

.source-panel span {
  color: var(--muted);
  font-size: 13px;
}

.field {
  display: grid;
  gap: 8px;
  padding: 12px;
}

.field span {
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}

.field input,
.field select {
  width: 100%;
  min-height: 44px;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 0 12px;
  background: #fff;
  color: var(--ink);
}

.field input:focus,
.field select:focus,
button:focus-visible {
  outline: 3px solid rgba(15, 118, 110, 0.24);
  outline-offset: 2px;
}

.chapter-list {
  display: grid;
  gap: 8px;
}

.chapter-button {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 8px 10px;
  background: var(--panel);
  color: var(--ink);
  text-align: left;
}

.chapter-button span:first-child {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.chapter-button span:last-child {
  flex: 0 0 auto;
  color: var(--muted);
  font-size: 12px;
}

.chapter-button.is-active {
  border-color: var(--teal);
  background: var(--teal-soft);
}

.workspace {
  min-width: 0;
}

.toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
}

.result-title {
  min-width: 0;
}

.result-title strong {
  display: block;
  font-size: 20px;
}

.result-title span {
  display: block;
  margin-top: 3px;
  color: var(--muted);
  font-size: 13px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.segmented {
  flex: 0 0 auto;
  display: inline-grid;
  grid-template-columns: repeat(2, minmax(68px, 1fr));
  padding: 4px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.segmented button {
  min-height: 34px;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--muted);
}

.segmented button.is-active {
  background: var(--ink);
  color: #fff;
}

.question-list {
  display: grid;
  gap: 12px;
}

.question-card {
  padding: 16px;
}

.card-head,
.card-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  color: var(--muted);
  font-size: 12px;
}

.pill {
  display: inline-flex;
  align-items: center;
  min-height: 24px;
  padding: 0 8px;
  border-radius: 999px;
  background: #eef0f2;
}

.pill.chapter {
  background: var(--teal-soft);
  color: #07534d;
}

.pill.learned {
  background: #fff1d6;
  color: var(--amber);
}

.question-text {
  margin: 12px 0 14px;
  font-size: clamp(18px, 2vw, 22px);
  line-height: 1.55;
  font-weight: 750;
  letter-spacing: 0;
}

.answer {
  margin-top: 12px;
  padding: 14px;
  border-left: 4px solid var(--teal);
  border-radius: 6px;
  background: #fbfcfc;
  line-height: 1.75;
  white-space: pre-wrap;
}

.tip {
  margin-top: 10px;
  color: var(--coral);
  font-weight: 700;
}

.primary-action,
.secondary-action,
.ghost-action,
.icon-button {
  border: 1px solid var(--line);
  border-radius: 8px;
  min-height: 40px;
  padding: 0 12px;
  background: var(--panel);
  color: var(--ink);
}

.primary-action {
  border-color: var(--teal);
  background: var(--teal);
  color: #fff;
  font-weight: 700;
}

.secondary-action:hover,
.ghost-action:hover,
.icon-button:hover,
.primary-action:hover {
  transform: translateY(-1px);
}

.secondary-action.is-learned,
.ghost-action.is-learned {
  border-color: var(--amber);
  background: #fff8e8;
  color: var(--amber);
}

.flash-view {
  min-height: 58vh;
  display: grid;
  place-items: start center;
}

.flash-card {
  width: min(760px, 100%);
  padding: clamp(18px, 4vw, 32px);
}

.flash-card h2 {
  min-height: 118px;
  margin: 18px 0;
  font-size: clamp(24px, 4vw, 38px);
  line-height: 1.34;
  letter-spacing: 0;
}

.flash-actions {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) 48px;
  gap: 10px;
  margin-top: 18px;
}

.icon-button {
  width: 48px;
  padding: 0;
  font-size: 26px;
}

.flash-card .ghost-action {
  width: 100%;
  margin-top: 10px;
}

.empty-state {
  display: grid;
  gap: 6px;
  place-items: center;
  min-height: 240px;
  padding: 24px;
  color: var(--muted);
}

.empty-state strong {
  color: var(--ink);
  font-size: 20px;
}

[hidden] {
  display: none !important;
}

@media (max-width: 900px) {
  .topbar {
    position: static;
    align-items: flex-start;
    flex-direction: column;
  }

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

  .layout {
    grid-template-columns: 1fr;
    padding-top: 16px;
  }

  .sidebar {
    position: static;
  }

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

@media (max-width: 560px) {
  .layout {
    padding-inline: 12px;
  }

  .toolbar,
  .card-head,
  .card-actions {
    align-items: stretch;
    flex-direction: column;
  }

  .segmented {
    width: 100%;
  }

  .chapter-list {
    grid-template-columns: 1fr;
    max-height: 220px;
    overflow: auto;
  }

  .question-card {
    padding: 14px;
  }

  .flash-actions {
    grid-template-columns: 44px minmax(0, 1fr) 44px;
  }

  .icon-button {
    width: 44px;
  }
}