:root {
  color-scheme: light;
  --bg: #f5f0ea;
  --panel: rgba(255, 255, 255, .72);
  --panel-strong: rgba(255, 255, 255, .84);
  --panel-soft: rgba(247, 248, 250, .62);
  --ink: #15171a;
  --muted: #68707d;
  --faint: #9aa1ad;
  --line: rgba(228, 231, 235, .74);
  --line-strong: rgba(207, 213, 220, .86);
  --accent: #b4232a;
  --accent-soft: #fff0f1;
  --teal: #0f766e;
  --teal-soft: #e8f6f3;
  --amber: #a16207;
  --amber-soft: #fff7df;
  --danger: #b4232a;
  --danger-soft: #fff0f1;
  --shadow: 0 18px 50px rgba(19, 23, 31, .08);
  --radius: 8px;
  --glass-blur: 18px;
  font-family: "Inter", "Segoe UI", "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #111315;
  --panel: rgba(24, 27, 31, .72);
  --panel-strong: rgba(24, 27, 31, .86);
  --panel-soft: rgba(32, 36, 42, .58);
  --ink: #f3f5f7;
  --muted: #a8b0ba;
  --faint: #77808c;
  --line: #303640;
  --line-strong: #454d58;
  --accent: #f0646b;
  --accent-soft: rgba(240, 100, 107, .12);
  --teal: #36c2b4;
  --teal-soft: rgba(54, 194, 180, .13);
  --amber: #f0b84d;
  --amber-soft: rgba(240, 184, 77, .14);
  --danger: #ff7a7f;
  --danger-soft: rgba(255, 122, 127, .13);
  --shadow: 0 20px 60px rgba(0, 0, 0, .35);
}

* { box-sizing: border-box; }
html { min-width: 320px; background: var(--bg); }
body {
  margin: 0;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, .46), rgba(255, 255, 255, .18) 42%, rgba(255, 255, 255, .34)),
    url("./04d88c20-fb34-446d-9c80-cc8bf701e056.png") center / cover fixed no-repeat,
    var(--bg);
  color: var(--ink);
  font-size: 15px;
  line-height: 1.6;
}
[data-theme="dark"] body {
  background:
    linear-gradient(180deg, rgba(0, 0, 0, .46), rgba(0, 0, 0, .24) 42%, rgba(0, 0, 0, .5)),
    url("./04d88c20-fb34-446d-9c80-cc8bf701e056.png") center / cover fixed no-repeat,
    var(--bg);
}
button, input, textarea, select {
  font: inherit;
  color: inherit;
}
button {
  border: 0;
  cursor: pointer;
}
.app-shell {
  min-height: 100vh;
  padding: 18px;
}
.layout {
  display: grid;
  grid-template-columns: 248px minmax(0, 1fr) 280px;
  gap: 18px;
  max-width: 1440px;
  margin: 0 auto;
}
.sidebar,
.study-panel,
.inspector {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  backdrop-filter: blur(var(--glass-blur)) saturate(135%);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(135%);
}
.sidebar,
.inspector {
  position: sticky;
  top: 18px;
  height: calc(100vh - 36px);
  overflow: auto;
  scrollbar-width: thin;
}
.brand {
  padding: 20px 18px 16px;
  border-bottom: 1px solid var(--line);
}
.brand-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.brand h1 {
  margin: 0;
  font-size: 22px;
  line-height: 1.15;
  letter-spacing: 0;
}
.brand p {
  margin: 8px 0 0;
  color: var(--muted);
  font-size: 13px;
}
.view-tabs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-top: 14px;
}
.view-tabs button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  min-height: 38px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  font-size: 13px;
  font-weight: 700;
}
.view-tabs button:hover { background: var(--panel-soft); }
.view-tabs button.active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
}
.icon-btn {
  width: 36px;
  height: 36px;
  flex: 0 0 36px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  background: var(--panel);
  border-radius: 8px;
}
.icon-btn:hover { border-color: var(--line-strong); background: var(--panel-soft); }
.nav-section { padding: 14px; border-bottom: 1px solid var(--line); }
.section-title {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
}
.nav-list { display: grid; gap: 6px; }
.nav-item {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 9px 10px;
  border-radius: 8px;
  background: transparent;
  text-align: left;
}
.nav-item:hover { background: var(--panel-soft); }
.nav-item.active {
  color: var(--accent);
  background: var(--accent-soft);
  font-weight: 700;
}
.count {
  color: var(--faint);
  font-size: 12px;
  font-weight: 600;
}
.nav-item.active .count { color: var(--accent); }
.type-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
}
.chip {
  min-height: 36px;
  padding: 7px 9px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  font-size: 13px;
}
.chip:hover { background: var(--panel-soft); }
.chip.active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 700;
}
.study-panel { min-width: 0; overflow: hidden; }
.topbar {
  display: grid;
  grid-template-columns: minmax(160px, 1fr) auto auto;
  gap: 10px;
  padding: 14px;
  border-bottom: 1px solid var(--line);
  background: var(--panel-soft);
  backdrop-filter: blur(var(--glass-blur)) saturate(135%);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(135%);
}
.timeline-topbar { grid-template-columns: minmax(160px, 1fr); }
.search-wrap { position: relative; min-width: 0; }
.search-wrap svg {
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--faint);
}
.search {
  width: 100%;
  height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel-strong);
  padding: 0 12px 0 40px;
  outline: none;
}
.search:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.select,
.input-small {
  height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel-strong);
  padding: 0 11px;
  outline: none;
}
.content { padding: 18px; }
.timeline-content { padding-bottom: 24px; }
.session-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 16px;
}
.kicker {
  margin: 0 0 5px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}
.session-head h2 {
  margin: 0;
  font-size: 28px;
  line-height: 1.22;
  letter-spacing: 0;
}
.progress-box {
  min-width: 180px;
  text-align: right;
}
.progress-text { color: var(--muted); font-size: 13px; }
.bar {
  height: 8px;
  margin-top: 8px;
  background: var(--panel-soft);
  border-radius: 999px;
  overflow: hidden;
}
.bar span {
  display: block;
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--teal));
  transition: width .2s ease;
}
.question-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel-strong);
  backdrop-filter: blur(var(--glass-blur)) saturate(135%);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(135%);
}
.timeline-list {
  display: grid;
  gap: 10px;
}
.timeline-card {
  display: grid;
  grid-template-columns: 130px minmax(0, 1fr);
  gap: 16px;
  padding: 15px 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel-strong);
  backdrop-filter: blur(var(--glass-blur)) saturate(135%);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(135%);
}
.timeline-date {
  color: var(--accent);
  font-weight: 800;
  line-height: 1.35;
}
.timeline-body h3 {
  margin: 0;
  font-size: 16px;
  line-height: 1.45;
  letter-spacing: 0;
}
.timeline-body ul {
  margin: 8px 0 0;
  padding-left: 18px;
  color: var(--muted);
}
.timeline-body li + li { margin-top: 4px; }
.question-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 16px;
  border-bottom: 1px solid var(--line);
}
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  min-width: 0;
}
.tag {
  display: inline-flex;
  align-items: center;
  min-height: 26px;
  padding: 3px 8px;
  border-radius: 7px;
  background: var(--panel-soft);
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
}
.tag.red { color: var(--accent); background: var(--accent-soft); }
.tag.green { color: var(--teal); background: var(--teal-soft); }
.tag.amber { color: var(--amber); background: var(--amber-soft); }
.stem {
  padding: 22px 22px 12px;
  font-size: 21px;
  font-weight: 700;
  line-height: 1.72;
}
.blank-input {
  width: min(220px, 100%);
  height: 38px;
  margin: 0 4px;
  border: 0;
  border-bottom: 2px solid var(--line-strong);
  background: var(--panel-soft);
  border-radius: 6px 6px 0 0;
  padding: 0 8px;
  text-align: center;
  outline: none;
}
.blank-input:focus { border-color: var(--accent); }
.blank-input.ok { border-color: var(--teal); background: var(--teal-soft); }
.blank-input.no { border-color: var(--danger); background: var(--danger-soft); }
.answer-area { padding: 8px 22px 22px; }
.options { display: grid; gap: 10px; }
.option {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  gap: 10px;
  align-items: start;
  width: 100%;
  min-height: 48px;
  padding: 11px 13px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel-strong);
  text-align: left;
}
.option:hover { border-color: var(--line-strong); background: var(--panel-soft); }
.option.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.option.correct {
  border-color: var(--teal);
  background: var(--teal-soft);
}
.option.wrong {
  border-color: var(--danger);
  background: var(--danger-soft);
}
.letter {
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
  border-radius: 7px;
  background: var(--panel-soft);
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
}
.option.selected .letter,
.option.correct .letter,
.option.wrong .letter {
  background: var(--panel);
}
.judge-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}
.textarea {
  width: 100%;
  min-height: 150px;
  resize: vertical;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  padding: 12px;
  outline: none;
}
.textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.answer-box {
  display: none;
  margin-top: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel-soft);
  padding: 13px;
}
.answer-box.show { display: block; }
.answer-box h3 {
  margin: 0 0 8px;
  font-size: 14px;
}
.answer-list {
  margin: 0;
  padding-left: 20px;
}
.answer-list li { margin: 3px 0; }
.feedback {
  margin-top: 14px;
  border-radius: 8px;
  padding: 12px 14px;
  font-weight: 700;
}
.feedback.ok { color: var(--teal); background: var(--teal-soft); }
.feedback.no { color: var(--danger); background: var(--danger-soft); }
.feedback.half { color: var(--amber); background: var(--amber-soft); }
.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 14px 16px;
  border-top: 1px solid var(--line);
  background: var(--panel-soft);
}
.btn {
  min-height: 42px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 9px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  font-weight: 700;
}
.btn:hover { border-color: var(--line-strong); }
.btn.primary {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}
.btn.ghost { background: transparent; }
.btn:disabled {
  cursor: not-allowed;
  opacity: .55;
}
.empty {
  padding: 50px 20px;
  text-align: center;
  color: var(--muted);
}
.empty h2 { color: var(--ink); margin: 0 0 8px; }
.inspector { padding: 14px; }
.stat-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}
.stat {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px;
  background: var(--panel);
}
.stat b {
  display: block;
  font-size: 24px;
  line-height: 1.1;
}
.stat span {
  color: var(--muted);
  font-size: 12px;
}
.panel-block { margin-top: 16px; }
.panel-block h3 {
  margin: 0 0 9px;
  font-size: 14px;
}
.mini-list { display: grid; gap: 8px; }
.mini-item {
  width: 100%;
  padding: 9px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  text-align: left;
  color: var(--muted);
  font-size: 13px;
}
.mini-item:hover { border-color: var(--line-strong); color: var(--ink); }
.shortcuts {
  display: grid;
  gap: 7px;
  color: var(--muted);
  font-size: 12px;
}
.shortcut {
  display: flex;
  justify-content: space-between;
  gap: 10px;
}
kbd {
  min-width: 22px;
  display: inline-grid;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-bottom-width: 2px;
  border-radius: 5px;
  padding: 1px 5px;
  color: var(--ink);
  background: var(--panel-soft);
  font-size: 11px;
  font-family: inherit;
}
.mobile-filter { display: none; }
.toast {
  position: fixed;
  left: 50%;
  bottom: 18px;
  transform: translateX(-50%);
  z-index: 30;
  max-width: min(460px, calc(100vw - 28px));
  padding: 10px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  box-shadow: var(--shadow);
  color: var(--ink);
  opacity: 0;
  pointer-events: none;
  transition: opacity .16s ease, transform .16s ease;
}
.toast.show {
  opacity: 1;
  transform: translate(-50%, -6px);
}
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 1180px) {
  .layout { grid-template-columns: 220px minmax(0, 1fr); }
  .inspector {
    position: static;
    grid-column: 1 / -1;
    height: auto;
  }
}

@media (max-width: 820px) {
  .app-shell { padding: 10px; }
  .layout { display: block; }
  .sidebar {
    position: static;
    height: auto;
    margin-bottom: 10px;
  }
  .sidebar .nav-section { display: none; }
  .mobile-filter {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 8px;
    padding: 12px;
    border-top: 1px solid var(--line);
  }
  .study-panel { margin-bottom: 10px; }
  .topbar { grid-template-columns: 1fr; }
  .content { padding: 12px; }
  .session-head { display: block; }
  .session-head h2 { font-size: 22px; }
  .progress-box {
    min-width: 0;
    text-align: left;
    margin-top: 12px;
  }
  .stem {
    padding: 18px 16px 10px;
    font-size: 18px;
  }
  .answer-area { padding: 8px 16px 18px; }
  .question-meta {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 36px;
    align-items: start;
    padding: 12px;
  }
  .judge-grid { grid-template-columns: 1fr; }
  .actions { padding: 12px; }
  .btn { flex: 1 1 auto; }
  .inspector { height: auto; }
}