:root {
  --bg-0: #f8fafc;
  --bg-1: #f1f5f9;
  --bg-2: #ebf1f7;
  --panel: rgba(255, 255, 255, 0.9);
  --panel-strong: rgba(255, 255, 255, 0.98);
  --text: #1f2937;
  --muted: #64748b;
  --accent: #b45309;
  --accent-2: #1d4ed8;
  --accent-3: #0f766e;
  --border: rgba(148, 163, 184, 0.16);
  --danger: #b45309;
  --shadow: 0 10px 24px rgba(15, 23, 42, 0.06);
  --radius: 16px;
}

* {
  box-sizing: border-box;
}

html,
body {
  min-height: 100%;
}

body {
  margin: 0;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.04), transparent 28%),
    radial-gradient(circle at right 20%, rgba(180, 83, 9, 0.04), transparent 26%),
    linear-gradient(135deg, var(--bg-0) 0%, var(--bg-1) 45%, var(--bg-2) 100%);
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", "Helvetica Neue", Arial, sans-serif;
  font-size: 15.5px;
  line-height: 1.55;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(37, 99, 235, 0.02) 1px, transparent 1px),
    linear-gradient(90deg, rgba(37, 99, 235, 0.02) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.12), transparent 82%);
}

button,
textarea {
  font: inherit;
}

.app-shell {
  display: grid;
  grid-template-columns: minmax(240px, 270px) minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  align-self: start;
  height: 100vh;
  overflow: auto;
  padding: 22px 18px;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.94), rgba(248, 250, 252, 0.9));
  border-right: 1px solid var(--border);
  backdrop-filter: blur(10px);
}

.brand {
  margin-bottom: 22px;
  padding-bottom: 18px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.12);
}

.brand-kicker,
.eyebrow {
  margin: 0 0 8px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.7rem;
  color: var(--accent-2);
}

.brand h1 {
  margin: 0 0 10px;
  font-family: inherit;
  font-size: 1.4rem;
  line-height: 1.2;
  font-weight: 650;
}

.brand p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.nav-group {
  margin-top: 18px;
}

.nav-group h2 {
  margin: 0 0 12px;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 650;
  color: var(--muted);
}

.nav-list {
  display: grid;
  gap: 10px;
}

.nav-btn {
  width: 100%;
  border: 1px solid rgba(74, 93, 122, 0.12);
  background: rgba(255, 255, 255, 0.92);
  color: var(--text);
  border-radius: 14px;
  padding: 11px 12px;
  text-align: left;
  cursor: pointer;
  transition: transform 0.16s ease, border-color 0.16s ease, background 0.16s ease, box-shadow 0.16s ease;
}

.nav-btn:hover {
  transform: translateY(-1px);
  border-color: rgba(37, 99, 235, 0.22);
}

.nav-btn.active {
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.12), rgba(217, 119, 6, 0.08));
  border-color: rgba(37, 99, 235, 0.28);
  box-shadow: 0 10px 24px rgba(16, 24, 40, 0.06);
}

.nav-btn .title {
  display: block;
  font-weight: 600;
  font-size: 0.95rem;
}

.nav-btn .meta {
  display: block;
  margin-top: 4px;
  font-size: 0.8rem;
  color: var(--muted);
}

.workspace {
  padding: 16px 18px 28px;
}

.workspace-topbar {
  position: sticky;
  top: 12px;
  z-index: 20;
  display: grid;
  gap: 10px;
  margin-bottom: 16px;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: rgba(248, 250, 252, 0.84);
  backdrop-filter: blur(12px);
  box-shadow: var(--shadow);
}

.workspace-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 0;
}

.workspace-header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.workspace-header h2 {
  margin: 0 0 6px;
  font-family: inherit;
  font-size: clamp(1.2rem, 1.4vw, 1.65rem);
  font-weight: 650;
  letter-spacing: -0.02em;
}

.workspace-header p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.status-chip {
  flex: 0 0 auto;
  border: 1px solid rgba(5, 150, 105, 0.16);
  background: rgba(5, 150, 105, 0.06);
  color: #0f766e;
  border-radius: 999px;
  padding: 6px 10px;
  font-size: 0.8rem;
}

.tabs {
  display: inline-flex;
  gap: 10px;
  padding: 4px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.76);
  border: 1px solid rgba(148, 163, 184, 0.14);
  box-shadow: none;
}

.tab-btn {
  border: 0;
  background: transparent;
  color: var(--muted);
  padding: 8px 12px;
  border-radius: 12px;
  cursor: pointer;
  font-size: 0.92rem;
  transition: background 0.16s ease, color 0.16s ease, transform 0.16s ease;
}

.tab-btn:hover {
  transform: translateY(-1px);
}

.tab-btn.active {
  color: var(--text);
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.13), rgba(217, 119, 6, 0.08));
}

.tab-panel {
  display: none;
  margin-top: 0;
}

.tab-panel.active {
  display: block;
  animation: panel-fade 0.2s ease;
}

.panel-grid {
  display: grid;
  grid-template-columns: minmax(280px, 330px) minmax(0, 1fr);
  gap: 14px;
  align-items: start;
}

.panel-grid-secondary {
  margin-top: 14px;
}

.conversation-card,
.revision-question,
.revision-result-summary,
.revision-result-item {
  border-radius: 14px;
  border: 1px solid var(--border);
  background: var(--panel-strong);
  box-shadow: var(--shadow);
}

.conversation-card {
  display: grid;
  gap: 14px;
  padding: 16px;
}

.revision-workflow {
  display: grid;
  gap: 14px;
}

.revision-workflow-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 18px;
  padding: 16px 18px;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.9);
  box-shadow: var(--shadow);
}

.revision-kicker {
  margin: 0 0 8px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.7rem;
  color: var(--accent-2);
}

.revision-workflow-head h3 {
  margin: 0 0 6px;
  font-size: 1.02rem;
  font-weight: 650;
}

.revision-workflow-head p {
  margin: 0;
  color: var(--muted);
}

.revision-progress-wrap {
  min-width: min(300px, 36vw);
  display: grid;
  gap: 10px;
}

.revision-stepper {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.revision-step {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  padding: 6px 10px;
  border: 1px solid rgba(148, 163, 184, 0.18);
  background: rgba(248, 250, 252, 0.96);
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.04em;
}

.revision-step.active {
  border-color: rgba(37, 99, 235, 0.24);
  background: rgba(37, 99, 235, 0.08);
  color: var(--accent-2);
}

.revision-step.done {
  border-color: rgba(15, 118, 110, 0.2);
  background: rgba(15, 118, 110, 0.08);
  color: var(--accent-3);
}

.revision-progress-track {
  height: 8px;
  border-radius: 999px;
  overflow: hidden;
  background: rgba(148, 163, 184, 0.14);
}

.revision-progress-track span {
  display: block;
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(135deg, #2563eb, #0f766e);
  transition: width 0.2s ease;
}

.revision-progress-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  color: var(--muted);
  font-size: 0.86rem;
}

.revision-workflow-body {
  display: grid;
  gap: 14px;
}

.revision-stage {
  min-height: 220px;
}

.revision-actions-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.revision-actions-row .secondary-btn {
  background: linear-gradient(135deg, #0f766e, #0ea5e9);
}

.revision-actions-row .primary-btn {
  min-width: 220px;
}

.chat-thread {
  display: grid;
  gap: 12px;
  min-height: 220px;
}

.chat-message {
  max-width: 92%;
  padding: 12px 13px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: rgba(248, 250, 252, 0.96);
  box-shadow: 0 6px 14px rgba(15, 23, 42, 0.04);
}

.chat-message.user {
  margin-left: auto;
  background: rgba(29, 78, 216, 0.05);
  border-color: rgba(29, 78, 216, 0.14);
}

.chat-message.assistant {
  margin-right: auto;
}

.chat-role {
  display: block;
  margin-bottom: 6px;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--muted);
}

.chat-content > :first-child {
  margin-top: 0;
}

.chat-content > :last-child {
  margin-bottom: 0;
}

.composer {
  padding-top: 14px;
  border-top: 1px solid rgba(148, 163, 184, 0.14);
  display: grid;
  gap: 10px;
}

.revision-quiz-header {
  padding-bottom: 12px;
  margin-bottom: 14px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.14);
}

.revision-quiz-header h3 {
  margin: 0 0 4px;
  font-size: 1rem;
  font-weight: 650;
}

.revision-quiz-header p {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

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

.revision-question {
  padding: 14px;
  box-shadow: none;
  background: rgba(255, 255, 255, 0.96);
}

.revision-question-head {
  display: grid;
  gap: 8px;
  margin-bottom: 10px;
}

.revision-question-number {
  display: inline-flex;
  width: fit-content;
  align-items: center;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(37, 99, 235, 0.08);
  color: var(--accent-2);
  font-size: 0.75rem;
  font-weight: 650;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.revision-question-text {
  font-size: 0.98rem;
}

.revision-answer-host {
  display: grid;
  gap: 8px;
}

.revision-choice {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  padding: 9px 10px;
  border-radius: 12px;
  border: 1px solid rgba(148, 163, 184, 0.16);
  background: rgba(248, 250, 252, 0.92);
}

.revision-choice input {
  margin-top: 3px;
}

.revision-choice span {
  line-height: 1.45;
}

.revision-result-summary {
  padding: 16px;
}

.revision-score {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
}

.revision-summary-text {
  margin-top: 10px;
  color: var(--text);
}

.revision-result-list {
  display: grid;
  gap: 10px;
  margin-top: 12px;
}

.revision-result-item {
  padding: 12px 14px;
  background: rgba(255, 255, 255, 0.96);
  box-shadow: none;
}

.revision-result-item strong {
  display: block;
  margin-bottom: 4px;
}

.revision-result-feedback {
  color: var(--muted);
}

.card,
.content-card {
  border-radius: 14px;
  border: 1px solid var(--border);
  background: var(--panel);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
}

.card {
  padding: 18px;
}

.card h3 {
  margin: 0 0 10px;
  font-family: inherit;
  font-size: 1rem;
  font-weight: 650;
}

.card p {
  margin: 0 0 14px;
  color: var(--muted);
  line-height: 1.55;
}

.content-card {
  min-height: 260px;
  padding: 20px;
  overflow: auto;
  color: var(--text);
  background: var(--panel-strong);
}

.content-card h1,
.content-card h2,
.content-card h3 {
  margin-top: 1.2em;
  margin-bottom: 0.5em;
  font-family: inherit;
  letter-spacing: -0.01em;
}

.content-card p,
.content-card li {
  line-height: 1.65;
}

.content-card ul,
.content-card ol {
  padding-left: 1.4rem;
}

.content-card code {
  padding: 0.15rem 0.35rem;
  border-radius: 6px;
  background: rgba(148, 163, 184, 0.12);
}

.content-card pre {
  overflow: auto;
  padding: 12px;
  border-radius: 12px;
  background: rgba(248, 250, 252, 0.95);
  border: 1px solid rgba(74, 93, 122, 0.12);
}

.content-card blockquote {
  margin: 1rem 0;
  padding: 0.8rem 0.95rem;
  border-left: 4px solid var(--accent-2);
  background: rgba(37, 99, 235, 0.05);
  color: var(--text);
  border-radius: 0 12px 12px 0;
}

.figure-container {
  margin-bottom: 1rem;
  padding: 0.75rem;
  border-radius: 12px;
  border: 1px solid rgba(74, 93, 122, 0.12);
  background: rgba(255, 255, 255, 0.82);
  overflow: auto;
}

.figure-container svg {
  display: block;
  max-width: 100%;
  height: auto;
}

textarea {
  width: 100%;
  min-height: 124px;
  padding: 12px 12px;
  color: var(--text);
  border: 1px solid rgba(74, 93, 122, 0.16);
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.92);
  resize: vertical;
}

textarea::placeholder {
  color: rgba(93, 107, 130, 0.72);
}

textarea:focus {
  outline: none;
  border-color: rgba(37, 99, 235, 0.5);
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
}

.card-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 12px;
}

.quick-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}

.quick-btn {
  border: 1px solid rgba(74, 93, 122, 0.14);
  background: rgba(255, 255, 255, 0.8);
  color: var(--text);
  border-radius: 999px;
  padding: 8px 10px;
  cursor: pointer;
  font-size: 0.86rem;
  transition: transform 0.14s ease, background 0.14s ease, border-color 0.14s ease;
}

.quick-btn:hover {
  transform: translateY(-1px);
  border-color: rgba(37, 99, 235, 0.24);
  background: rgba(37, 99, 235, 0.06);
}

.quick-btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
}

.primary-btn,
.secondary-btn {
  border: 0;
  border-radius: 12px;
  padding: 11px 14px;
  cursor: pointer;
  color: #fff;
  transition: transform 0.16s ease, filter 0.16s ease, box-shadow 0.16s ease;
}

.primary-btn {
  background: linear-gradient(135deg, #2563eb, #d97706);
  box-shadow: 0 10px 18px rgba(37, 99, 235, 0.14);
}

.secondary-btn {
  background: linear-gradient(135deg, #0f766e, #0ea5e9);
  box-shadow: 0 10px 18px rgba(14, 165, 233, 0.12);
}

.app-shell.sidebar-collapsed .sidebar {
  display: none;
}

.app-shell.sidebar-collapsed {
  grid-template-columns: 1fr;
}

.primary-btn:hover,
.secondary-btn:hover {
  transform: translateY(-1px);
  filter: brightness(1.04);
}

.primary-btn:disabled,
.secondary-btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
}

.loading {
  color: var(--muted);
  font-style: italic;
}

.error {
  color: var(--danger);
}

.empty-state {
  color: var(--muted);
}

.katex {
  font-size: 1.03em;
}

.content-card h1:first-child,
.content-card h2:first-child,
.content-card h3:first-child,
.content-card p:first-child {
  margin-top: 0;
}

@keyframes panel-fade {
  from {
    opacity: 0;
    transform: translateY(4px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (max-width: 1080px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: relative;
    height: auto;
    border-right: 0;
    border-bottom: 1px solid var(--border);
  }

  .workspace {
    padding: 16px 14px 24px;
  }

  .workspace-topbar {
    top: 8px;
    padding: 10px 12px;
  }

  .workspace-header {
    flex-direction: column;
  }

  .workspace-header-actions {
    width: 100%;
    justify-content: flex-start;
  }

  .revision-workflow-head {
    flex-direction: column;
  }

  .revision-progress-wrap {
    min-width: 100%;
  }

  .panel-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  .workspace-topbar {
    gap: 8px;
  }

  .workspace-header h2 {
    font-size: 1.2rem;
  }

  .tabs {
    display: flex;
    width: 100%;
    justify-content: stretch;
  }

  .tab-btn {
    flex: 1 1 0;
  }

  .card,
  .content-card {
    border-radius: 14px;
  }

  .chat-message {
    max-width: 100%;
  }

  .revision-actions-row .primary-btn {
    min-width: 100%;
  }
}