:root {
  /* Default to dark palette; light is provided via [data-theme="light"] */
  --bg: #0f172a;
  --bg-panel: #111827;
  --text: #e5e7eb;
  --muted: #9ca3af;
  --accent: #22c55e;
  --accent-2: #60a5fa;
  --danger: #ef4444;
  --border: #1f2937;
  --code-bg: #0b1022;

  /* Design tokens */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;

  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;

  --shadow-1: 0 1px 2px rgba(0,0,0,0.2);
  --shadow-2: 0 4px 16px rgba(0,0,0,0.25);
}

/* Light theme overrides (toggled via data-theme attr on html) */
[data-theme="light"] {
  --bg: #f9fafb;
  --bg-panel: #ffffff;
  --text: #0f172a;
  --muted: #4b5563;
  --accent: #059669;
  --accent-2: #2563eb;
  --danger: #dc2626;
  --border: #e5e7eb;
  --code-bg: #f3f4f6;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  line-height: 1.5;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 16px;
}

.site-header, .site-footer {
  background: linear-gradient(180deg, rgba(255,255,255,0.04), rgba(255,255,255,0.00));
  border-bottom: 1px solid var(--border);
}

.site-footer {
  border-top: 1px solid var(--border);
  border-bottom: none;
  margin-top: 32px;
}

.site-header .container,
.site-footer .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand a {
  color: var(--text);
  text-decoration: none;
}

.site-header nav a {
  color: var(--muted);
  margin-left: 12px;
  text-decoration: none;
  font-weight: 500;
}

.site-header nav a:hover {
  color: var(--text);
}

.repo {
  color: var(--accent-2) !important;
}

h1, h2, h3 {
  margin: 16px 0 8px;
}

.badge {
  display: inline-block;
  background: rgba(96, 165, 250, 0.12);
  color: var(--accent-2);
  border: 1px solid rgba(96, 165, 250, 0.4);
  border-radius: 999px;
  padding: 2px 8px;
  font-size: 12px;
  margin-right: 8px;
}

.path {
  color: var(--muted);
  font-size: 12px;
}

.btn {
  display: inline-block;
  background: linear-gradient(180deg, rgba(34, 197, 94, 0.2), rgba(34, 197, 94, 0.05));
  color: var(--text);
  border: 1px solid rgba(34, 197, 94, 0.5);
  border-radius: 8px;
  padding: 8px 12px;
  text-decoration: none;
  font-weight: 600;
  cursor: pointer;
}

.btn:hover {
  filter: brightness(1.1);
}

.btn.secondary {
  background: transparent;
  border-color: var(--border);
}

.panel {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px;
  margin: 16px 0;
}

.panel.error {
  border-color: rgba(239, 68, 68, 0.5);
  background: rgba(239, 68, 68, 0.08);
}

pre {
  margin: 0;
  overflow: auto;
  padding: 12px;
  background: var(--code-bg);
  border-radius: 8px;
  border: 1px solid var(--border);
}

.categories {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 16px;
}

.category {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px;
}

.demo-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.demo-item {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 8px;
  align-items: center;
  padding: 10px 0;
  border-bottom: 1px dashed var(--border);
}

.demo-item:last-child { border-bottom: none; }

.demo-title {
  font-weight: 600;
}

.demo-actions {
  display: flex;
  gap: 8px;
}

.demo-id {
  grid-column: 1 / -1;
  color: var(--muted);
  font-size: 12px;
}

.run-panel {
  grid-column: 1 / -1;
  margin-top: 8px;
}

.btn[disabled] {
  opacity: 0.6;
  cursor: not-allowed;
}

.demo-header {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 16px;
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
  margin-bottom: 12px;
}

a, a:visited { color: var(--accent-2); }
a:hover { opacity: 0.9; }

/* Improved header/nav and accessibility */
.primary-nav a {
  color: var(--muted);
  margin-left: 12px;
  text-decoration: none;
  font-weight: 600;
  padding: 6px 8px;
  border-radius: var(--radius-sm);
  transition: background-color 180ms ease, color 180ms ease, border-color 180ms ease;
}
.primary-nav a:hover {
  color: var(--text);
  background: rgba(96,165,250,0.08);
}
.primary-nav a.active {
  color: var(--text);
  background: rgba(96,165,250,0.12);
  border: 1px solid rgba(96,165,250,0.35);
}
.site-header .container,
.site-footer .container {
  flex-wrap: wrap;
}
.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-left: auto;
}

/* Skip link for keyboard users */
.skip-link {
  position: absolute;
  left: -9999px;
  top: auto;
  width: 1px;
  height: 1px;
  overflow: hidden;
}
.skip-link:focus {
  position: fixed;
  left: 16px;
  top: 12px;
  width: auto;
  height: auto;
  padding: 8px 12px;
  background: var(--bg-panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  z-index: 1000;
}

/* Focus visibility */
:where(a, button, input, select, textarea):focus-visible {
  outline: 2px solid var(--accent-2);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* Inputs */
:where(input, select, button) {
  font: inherit;
}
:where(select, input[type="number"], input[type="text"]) {
  transition: border-color 160ms ease, box-shadow 160ms ease;
}
:where(select, input[type="number"], input[type="text"]):focus {
  border-color: rgba(96,165,250,0.6);
  box-shadow: 0 0 0 2px rgba(96,165,250,0.2);
}

/* Buttons */
.btn {
  display: inline-block;
  background: linear-gradient(180deg, rgba(34, 197, 94, 0.2), rgba(34, 197, 94, 0.05));
  color: var(--text);
  border: 1px solid rgba(34, 197, 94, 0.5);
  border-radius: var(--radius-md);
  padding: 8px 12px;
  text-decoration: none;
  font-weight: 700;
  cursor: pointer;
  transition: transform 80ms ease, filter 160ms ease, border-color 160ms ease;
}
.btn:hover { filter: brightness(1.08); }
.btn:active { transform: translateY(1px); }
.btn.secondary {
  background: transparent;
  border-color: var(--border);
}
.btn.danger {
  background: linear-gradient(180deg, rgba(239,68,68,0.2), rgba(239,68,68,0.05));
  border-color: rgba(239,68,68,0.6);
}

/* Panels, cards and lists */
.panel {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 12px;
  margin: 16px 0;
  box-shadow: var(--shadow-1);
}
.category {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 12px;
  transition: border-color 160ms ease, transform 80ms ease, box-shadow 160ms ease;
}
.category:hover {
  border-color: rgba(96,165,250,0.4);
  transform: translateY(-1px);
  box-shadow: var(--shadow-1);
}
.demo-item {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 8px;
  align-items: center;
  padding: 10px 8px;
  border-bottom: 1px dashed var(--border);
  border-radius: var(--radius-sm);
  transition: background-color 120ms ease;
}
.demo-item:hover {
  background: rgba(96,165,250,0.04);
}

/* Inline code */
code {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0 6px;
}

/* Responsive nav stacking */
@media (max-width: 640px) {
  .primary-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
  }
  .site-header .container { gap: 8px; }
}

/* Visualization page */
.viz-controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 12px;
  align-items: center;
}
.viz-controls label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  color: var(--muted);
  font-size: 14px;
}
.viz-controls label.row {
  flex-direction: row;
  align-items: center;
  gap: 10px;
}
.viz-controls select, .viz-controls input[type="number"] {
  background: var(--bg-panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 8px;
}
.viz-controls input[type="range"] {
  accent-color: var(--accent);
}
.viz-buttons {
  grid-column: 1 / -1;
  display: flex;
  gap: 8px;
}

.viz-status {
  color: var(--muted);
  margin-bottom: 8px;
}

/* Bars visualization */
.bars {
  --bar-width: 4px;
  --bar-gap: 1px;
  --bar-height: 360px;
  display: flex;
  align-items: flex-end;
  gap: var(--bar-gap);
  height: var(--bar-height);
  min-height: 200px;
  width: 100%;
  border: 1px solid var(--border);
  background: var(--bg-panel);
  border-radius: 8px;
  padding: 8px;
  overflow: hidden;
}

.bars .bar {
  width: var(--bar-width);
  background: linear-gradient(180deg, rgba(96,165,250,0.2), rgba(96,165,250,0.08));
  border: 1px solid rgba(96,165,250,0.25);
  border-bottom: none;
  border-radius: 4px 4px 0 0;
  transition: height 40ms linear, background-color 40ms linear, border-color 40ms linear;
}

/* Highlights for operations */
.bars .bar.compare {
  background: rgba(96,165,250,0.5);
  border-color: rgba(96,165,250,0.8);
}
.bars .bar.swap, .bars .bar.shift {
  background: rgba(245,158,11,0.55);
  border-color: rgba(245,158,11,0.85);
}
.bars .bar.pivot {
  background: rgba(239,68,68,0.6);
  border-color: rgba(239,68,68,0.9);
}
.bars .bar.key {
  background: rgba(167,139,250,0.6);
  border-color: rgba(167,139,250,0.9);
}
.bars .bar.insert {
  background: rgba(34,197,94,0.55);
  border-color: rgba(34,197,94,0.85);
}

/* Pathfinding grid */
.grid {
  --rows: 20;
  --cols: 30;
  display: grid;
  grid-template-rows: repeat(var(--rows), 1fr);
  grid-template-columns: repeat(var(--cols), 1fr);
  gap: 1px;
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  width: 100%;
  max-height: 640px;
  padding: 8px;
}

.grid .cell {
  background: rgba(96,165,250,0.08);
  border: 1px solid rgba(31,41,55,0.9);
  border-radius: 3px;
  aspect-ratio: 1 / 1; /* keep cells roughly square */
  transition: background-color 60ms linear, border-color 60ms linear, box-shadow 60ms linear;
}

/* Walls and states */
.grid .cell.wall {
  background: rgba(31,41,55,0.95);
  border-color: rgba(15,23,42,1);
}

.grid .cell.open {
  background: rgba(96,165,250,0.35);
  border-color: rgba(96,165,250,0.75);
}

.grid .cell.closed {
  background: rgba(245,158,11,0.45);
  border-color: rgba(245,158,11,0.85);
}

.grid .cell.path {
  background: rgba(34,197,94,0.55);
  border-color: rgba(34,197,94,0.9);
  box-shadow: inset 0 0 0 2px rgba(34,197,94,0.5);
}

.grid .cell.current {
  background: rgba(239,68,68,0.6);
  border-color: rgba(239,68,68,0.95);
}

/* Start/goal markers overlay via box-shadow ring */
.grid .cell.start {
  box-shadow: inset 0 0 0 2px rgba(167,139,250,0.9);
}

.grid .cell.goal {
  box-shadow: inset 0 0 0 2px rgba(59,130,246,0.9);
}

/* Notes and small text helpers */
.notes {
  white-space: pre-wrap;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 14px;
  line-height: 1.4;
}

.small {
  color: var(--muted);
  font-size: 12px;
  margin-top: 4px;
}

/* Dashboard Enhancements */
.dashboard-header {
  margin-bottom: 1.5rem;
}

.dashboard-title h2 {
  font-size: 1.875rem;
  font-weight: 700;
  color: var(--text);
}

.dashboard-stats {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  font-size: 0.875rem;
  color: var(--muted);
}

.badge-info {
  background-color: rgba(59, 130, 246, 0.1);
  color: #60a5fa;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-weight: 500;
}

.badge-success {
  background-color: rgba(34, 197, 94, 0.1);
  color: #22c55e;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-weight: 500;
}

.badge-warning {
  background-color: rgba(245, 158, 11, 0.1);
  color: #f59e0b;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-weight: 500;
}

.dashboard-controls {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

@media (min-width: 1024px) {
  .dashboard-controls {
    flex-direction: row;
    align-items: center;
  }
}

.search-container {
  position: relative;
}

.search-input {
  width: 100%;
  padding: 0.75rem 1rem;
  padding-left: 2.5rem;
  border-radius: var(--radius-md);
  background-color: var(--bg-panel);
  border: 1px solid var(--border);
  color: var(--text);
  transition: all 150ms ease-in-out;
}

.search-input:focus {
  outline: none;
  border-color: var(--accent-2);
  box-shadow: 0 0 0 3px rgba(96, 165, 250, 0.2);
}

.search-icon {
  position: absolute;
  top: 50%;
  left: 0.75rem;
  transform: translateY(-50%);
  color: var(--muted);
}

.filter-controls {
  display: flex;
  gap: 0.5rem;
}

.filter-select {
  padding: 0.75rem 1rem;
  border-radius: var(--radius-md);
  background-color: var(--bg-panel);
  border: 1px solid var(--border);
  color: var(--text);
}

.view-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
  margin-top: 1rem;
}

.view-tab {
  padding: 0.75rem 1.25rem;
  cursor: pointer;
  border: none;
  background: none;
  color: var(--muted);
  font-weight: 600;
  border-bottom: 2px solid transparent;
  transition: all 150ms ease-in-out;
}

.view-tab:hover {
  color: var(--text);
}

.view-tab.active {
  color: var(--accent-2);
  border-bottom-color: var(--accent-2);
}

.content-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.content-card {
  background-color: var(--bg-panel);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  transition: all 150ms ease-in-out;
}

.content-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-2);
  border-color: rgba(96, 165, 250, 0.4);
}

.card-header {
  padding: 0.75rem 1rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  border-bottom: 1px solid var(--border);
}

.card-status-indicator {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.card-status-indicator.complete { background-color: var(--accent); }
.card-status-indicator.partial { background-color: var(--accent-2); }
.card-status-indicator.todo { background-color: #f59e0b; }

.card-meta {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.75rem;
  color: var(--muted);
}

.card-category {
  font-weight: 500;
}

.difficulty-badge {
  padding: 0.125rem 0.5rem;
  border-radius: 9999px;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
}

.difficulty-badge.easy { background-color: rgba(34, 197, 94, 0.2); color: #22c55e; }
.difficulty-badge.medium { background-color: rgba(245, 158, 11, 0.2); color: #f59e0b; }
.difficulty-badge.hard { background-color: rgba(239, 68, 68, 0.2); color: #ef4444; }

.card-body {
  padding: 1rem;
  flex-grow: 1;
}

.card-title {
  font-size: 1.125rem;
  font-weight: 600;
  margin: 0 0 0.5rem;
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.375rem;
  margin-bottom: 0.75rem;
}

.tag {
  background-color: rgba(96, 165, 250, 0.1);
  color: #9ca3af;
  padding: 0.125rem 0.5rem;
  border-radius: 9999px;
  font-size: 0.75rem;
}

.card-description {
  font-size: 0.875rem;
  color: var(--muted);
  line-height: 1.6;
  margin-bottom: 1rem;
}

/* Removed old progress-indicator */
}

/* Removed old progress-bar */
  height: 6px;
  background-color: var(--border);
  border-radius: 9999px;
  overflow: hidden;
}

/* Removed old progress-fill */
  background-color: var(--accent-2);
  border-radius: 9999px;
}

/* Removed old progress-text */
  color: var(--muted);
  margin-top: 0.25rem;
}

.card-actions {
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--border);
  display: flex;
  gap: 0.5rem;
  align-items: center;
  justify-content: space-between;
}

.card-action-icons {
  display: flex;
  gap: 0.5rem;
  margin-left: auto;
}

.btn-primary {
  background-color: var(--accent);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-md);
  font-weight: 600;
  text-decoration: none;
  flex-grow: 1;
  text-align: center;
}

.btn-secondary {
  background-color: transparent;
  border: 1px solid var(--border);
  color: var(--muted);
  padding: 0.5rem 1rem;
  border-radius: var(--radius-md);
  font-weight: 600;
  text-decoration: none;
}

.btn-icon {
  background: none;
  border: none;
  color: var(--muted);
  cursor: pointer;
  padding: 0.25rem;
  border-radius: 50%;
}

.btn-icon:hover {
  background-color: var(--border);
  color: var(--text);
}

.btn-icon-labeled {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: transparent;
  border: 1px solid var(--border);
  color: var(--muted);
  cursor: pointer;
  padding: 0.4rem 0.75rem;
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  font-weight: 500;
  text-decoration: none;
  transition: background-color 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}

.btn-icon-labeled i {
  font-size: 0.9rem;
}

.btn-icon-labeled:hover {
  background-color: var(--border);
  color: var(--text);
  border-color: var(--accent-2);
}

.card-menu {
  position: relative;
  margin-left: auto;
}

.dropdown-menu {
  position: absolute;
  right: 0;
  top: 100%;
  background-color: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 0.5rem;
  min-width: 150px;
  z-index: 10;
  display: none;
}

.dropdown-menu.show {
  display: block;
}

.dropdown-menu a {
  display: block;
  padding: 0.5rem;
  color: var(--text);
  text-decoration: none;
  border-radius: var(--radius-sm);
}

.dropdown-menu a:hover {
  background-color: var(--border);
}

.demo-output-panel {
  padding: 1rem;
  border-top: 1px solid var(--border);
}

.demo-output-panel.error .output-header h4 {
  color: var(--danger);
}

.output-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

.output-header h4 {
  margin: 0;
  font-size: 0.875rem;
  font-weight: 600;
}

.demo-output {
  background-color: var(--code-bg);
  padding: 0.75rem;
  border-radius: var(--radius-sm);
  max-height: 200px;
  overflow-y: auto;
}


/* Search Overlay */
.search-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 50;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding-top: 10vh;
}

.search-results-container {
  background-color: var(--bg-panel);
  border-radius: var(--radius-lg);
  width: 90%;
  max-width: 600px;
  max-height: 80vh;
  display: flex;
  flex-direction: column;
}

.search-results-header {
  padding: 1rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.search-results-content {
  overflow-y: auto;
  padding: 0.5rem;
}

.search-result-item {
  padding: 0.75rem 1rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
}

.search-result-item:hover {
  background-color: var(--border);
}

.result-title {
  font-weight: 500;
}

.result-category {
  color: var(--muted);
  font-size: 0.875rem;
}

.no-results {
  padding: 2rem;
  text-align: center;
  color: var(--muted);
}