@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:ital,wght@0,500;0,600;0,700;1,500&family=Plus+Jakarta+Sans:wght@400;500;600;700&display=swap');

:root {
  --bg-page: hsl(40, 25%, 97%);
  --bg-surface: hsl(0, 0%, 100%);
  --bg-subtle: hsl(38, 22%, 93%);
  --bg-elevated: hsl(40, 30%, 99%);
  --text-main: hsl(220, 28%, 14%);
  --text-secondary: hsl(220, 14%, 38%);
  --text-muted: hsl(220, 10%, 52%);
  --border-color: hsl(35, 16%, 84%);
  --border-strong: hsl(35, 16%, 72%);
  --accent-primary: hsl(212, 82%, 38%);
  --accent-primary-hover: hsl(212, 85%, 31%);
  --accent-primary-fg: hsl(0, 0%, 100%);
  --accent-soft: hsl(212, 65%, 94%);
  --accent-amber: hsl(32, 88%, 42%);
  --accent-amber-soft: hsl(36, 90%, 94%);
  --success: hsl(152, 68%, 29%);
  --success-soft: hsl(150, 58%, 94%);
  --danger: hsl(356, 72%, 44%);
  --danger-soft: hsl(356, 78%, 95%);
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.05);
  --shadow-md: 0 6px 18px -4px rgba(15, 23, 42, 0.08);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --font-sans: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
}

html[data-theme="dark"] {
  --bg-page: hsl(222, 24%, 10%);
  --bg-surface: hsl(222, 22%, 14%);
  --bg-subtle: hsl(222, 20%, 18%);
  --bg-elevated: hsl(222, 22%, 16%);
  --text-main: hsl(210, 25%, 94%);
  --text-secondary: hsl(215, 16%, 72%);
  --text-muted: hsl(215, 12%, 55%);
  --border-color: hsl(220, 18%, 24%);
  --border-strong: hsl(220, 18%, 34%);
  --accent-primary: hsl(208, 86%, 54%);
  --accent-primary-hover: hsl(208, 88%, 62%);
  --accent-primary-fg: hsl(222, 28%, 10%);
  --accent-soft: hsl(212, 45%, 20%);
  --accent-amber: hsl(36, 90%, 60%);
  --accent-amber-soft: hsl(36, 45%, 19%);
  --success: hsl(152, 65%, 52%);
  --success-soft: hsl(152, 42%, 18%);
  --danger: hsl(356, 80%, 64%);
  --danger-soft: hsl(356, 45%, 20%);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.25);
  --shadow-md: 0 8px 24px -4px rgba(0, 0, 0, 0.4);
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--bg-page);
  color: var(--text-main);
  font-family: var(--font-sans);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

/* Header & Breadcrumb Navigation */
.site-header {
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 40;
  box-shadow: var(--shadow-sm);
}

.header-inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0.75rem 1.25rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.breadcrumb-nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.45rem;
  font-size: 0.875rem;
  font-weight: 500;
}

.breadcrumb-link {
  color: var(--text-secondary);
  padding: 0.25rem 0.55rem;
  border-radius: var(--radius-sm);
  transition: background-color 0.15s ease, color 0.15s ease;
}

.breadcrumb-link:hover {
  background-color: var(--bg-subtle);
  color: var(--text-main);
}

.breadcrumb-current {
  color: var(--accent-primary);
  background-color: var(--accent-soft);
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-sm);
  font-weight: 600;
}

.breadcrumb-sep {
  color: var(--text-muted);
  user-select: none;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.stat-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.8125rem;
  font-weight: 600;
  padding: 0.35rem 0.7rem;
  border-radius: var(--radius-sm);
  background: var(--bg-subtle);
  border: 1px solid var(--border-color);
  font-family: var(--font-mono);
}

.stat-badge.amber {
  background: var(--accent-amber-soft);
  color: var(--accent-amber);
  border-color: transparent;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  font-weight: 600;
  padding: 0.45rem 0.85rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-main);
  cursor: pointer;
  transition: all 0.15s ease;
}

.btn:hover {
  background: var(--bg-subtle);
  border-color: var(--border-strong);
}

.btn-primary {
  background: var(--accent-primary);
  color: var(--accent-primary-fg);
  border-color: var(--accent-primary);
}

.btn-primary:hover {
  background: var(--accent-primary-hover);
  border-color: var(--accent-primary-hover);
}

/* Main Container */
.container {
  max-width: 1280px;
  width: 100%;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 3rem;
  flex: 1;
}

/* Hero & Page Intro */
.page-hero {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.page-hero h1 {
  font-size: clamp(1.35rem, 2.5vw, 1.85rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.45rem;
}

.page-hero p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  max-width: 75ch;
}

/* Grid Cards for /home and /home/ktdt */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(310px, 1fr));
  gap: 1.15rem;
}

.course-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.35rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 1rem;
  box-shadow: var(--shadow-sm);
  transition: transform 0.16s ease, box-shadow 0.16s ease, border-color 0.16s ease;
}

.course-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-primary);
}

.card-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.2rem 0.55rem;
  border-radius: 6px;
  background: var(--accent-soft);
  color: var(--accent-primary);
  margin-bottom: 0.5rem;
}

.course-card h2, .course-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.35rem;
}

.course-card p {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.formula-pill {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  background: var(--bg-subtle);
  padding: 0.45rem 0.65rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  overflow-x: auto;
}

/* Workspace Layout for /home/ktdt/bai-3 */
.toolbar-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.pill-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.pill-btn {
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  font-weight: 600;
  padding: 0.45rem 0.8rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.15s ease;
}

.pill-btn:hover {
  color: var(--text-main);
  background: var(--bg-subtle);
}

.pill-btn.active {
  background: var(--accent-primary);
  color: var(--accent-primary-fg);
  border-color: var(--accent-primary);
}

.mode-Order-group {
  display: inline-flex;
  background: var(--bg-subtle);
  padding: 0.25rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  gap: 0.25rem;
}

.mode-btn {
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  font-weight: 600;
  padding: 0.38rem 0.75rem;
  border-radius: 6px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.15s ease;
}

.mode-btn.active {
  background: var(--bg-surface);
  color: var(--text-main);
  box-shadow: var(--shadow-sm);
}

.workspace-grid {
  display: grid;
  grid-template-columns: 5fr 7fr;
  gap: 1.25rem;
  align-items: start;
}

@media (max-width: 980px) {
  .workspace-grid {
    grid-template-columns: 1fr;
  }
}

.panel-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.15rem;
  box-shadow: var(--shadow-sm);
}

.panel-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding-bottom: 0.75rem;
  margin-bottom: 0.9rem;
  border-bottom: 1px solid var(--border-color);
}

/* Diagram Viewport */
.diagram-stage {
  min-height: 290px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 0.85rem;
}

.svg-diagram {
  width: 100%;
  max-width: 390px;
  height: auto;
  color: var(--text-main);
}

.svg-diagram text {
  fill: currentColor;
  font-family: var(--font-sans);
}

.svg-diagram line,
.svg-diagram polyline,
.svg-diagram circle,
.svg-diagram polygon {
  stroke: currentColor;
}

.specs-box {
  margin-top: 0.85rem;
  padding: 0.65rem 0.8rem;
  border-radius: var(--radius-sm);
  background: var(--bg-subtle);
  font-family: var(--font-mono);
  font-size: 0.79rem;
  color: var(--text-secondary);
}

/* Quiz Options */
.step-meta {
  font-size: 0.76rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent-primary);
  margin-bottom: 0.35rem;
}

.question-prompt {
  font-size: 0.98rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--text-main);
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  margin-bottom: 1rem;
}

.option-card {
  width: 100%;
  text-align: left;
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  padding: 0.75rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--bg-elevated);
  color: var(--text-main);
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  transition: all 0.14s ease;
}

.option-card:hover {
  border-color: var(--accent-primary);
  background: var(--accent-soft);
}

.option-card.correct {
  border-color: var(--success);
  background: var(--success-soft);
}

.option-card.wrong {
  border-color: var(--danger);
  background: var(--danger-soft);
}

.option-letter {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 700;
  width: 26px;
  height: 26px;
  border-radius: 6px;
  background: var(--bg-subtle);
  border: 1px solid var(--border-color);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.feedback-banner {
  padding: 0.95rem 1rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--bg-subtle);
  font-size: 0.86rem;
  line-height: 1.6;
}

.feedback-banner.success {
  border-color: var(--success);
  background: var(--success-soft);
}

.feedback-banner.danger {
  border-color: var(--danger);
  background: var(--danger-soft);
}

.hint-banner {
  padding: 0.75rem 0.9rem;
  margin-bottom: 0.85rem;
  border-radius: var(--radius-sm);
  background: var(--accent-amber-soft);
  border: 1px solid var(--accent-amber);
  font-size: 0.83rem;
}

/* Fill-in-the-blank & Twin Inputs */
.input-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(255px, 1fr));
  gap: 0.65rem;
  margin-bottom: 1rem;
}

.field-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 0.55rem 0.75rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--bg-elevated);
  font-size: 0.82rem;
  font-weight: 500;
}

.num-input {
  width: 105px;
  padding: 0.35rem 0.55rem;
  border-radius: 6px;
  border: 1px solid var(--border-strong);
  background: var(--bg-surface);
  color: var(--text-main);
  font-family: var(--font-mono);
  font-size: 0.84rem;
  font-weight: 600;
  text-align: right;
}

.num-input.ok {
  border: 2px solid var(--success);
  background: var(--success-soft);
}

.num-input.err {
  border: 2px solid var(--danger);
  background: var(--danger-soft);
}

.hidden {
  display: none !important;
}

.site-footer {
  border-top: 1px solid var(--border-color);
  background: var(--bg-surface);
  padding: 1rem 1.25rem;
  text-align: center;
  font-size: 0.8125rem;
  color: var(--text-muted);
}