:root {
  --bg: #0f1419;
  --surface: #1a2332;
  --surface-hover: #243047;
  --border: #2d3a4f;
  --text: #e8edf4;
  --muted: #8b9cb3;
  --accent: #3d9cf5;
  --accent-dim: #2b7fc4;
  --accent-glow: rgba(61, 156, 245, 0.2);
  --success: #34c759;
  --error: #ff5c5c;
  --warning: #f5a623;
  --radius: 10px;
  --font: "DM Sans", system-ui, -apple-system, sans-serif;
  --mono: "JetBrains Mono", "SF Mono", Consolas, monospace;
}

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

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  background: var(--bg);
  background-image:
    radial-gradient(ellipse 120% 80% at 50% -20%, rgba(61, 156, 245, 0.12), transparent),
    radial-gradient(ellipse 60% 40% at 100% 50%, rgba(61, 156, 245, 0.06), transparent);
  color: var(--text);
  line-height: 1.5;
}

a {
  color: var(--accent);
}

.page {
  max-width: 1180px;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 2.5rem;
}

/* ------------------------------------------------------------------ */
/* Graph viz panel                                                      */
/* ------------------------------------------------------------------ */

.graph-viz-panel h2 {
  margin-top: 0;
}

.graph-viz-toolbar {
  margin-bottom: 0.75rem;
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  align-items: center;
}

.graph-viz-panel {
  width: 100%;
}

.graph-viz-step {
  margin: 0 0 0.5rem;
  min-height: 1.25rem;
  font-size: 0.8125rem;
  color: var(--accent);
  font-family: var(--mono);
}

.graph-viz-host {
  position: relative;
  min-height: 340px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg);
  overflow: hidden;
  cursor: crosshair;
  transition: border-color 0.2s;
}

.graph-viz-host:hover {
  border-color: rgba(61, 156, 245, 0.4);
}

.graph-viz-host.dragging-edge {
  cursor: grabbing;
}

#graph-viz-canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.graph-viz-empty {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  margin: 0;
  padding: 1.5rem;
  text-align: center;
  color: var(--muted);
  font-size: 0.9375rem;
  pointer-events: none;
}

.graph-viz-empty .hint-icon {
  font-size: 2rem;
  opacity: 0.4;
}

/* ------------------------------------------------------------------ */
/* Playback controls                                                    */
/* ------------------------------------------------------------------ */

.playback-bar {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-top: 0.65rem;
  padding: 0.55rem 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.playback-bar[hidden] {
  display: none;
}

.playback-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--muted);
  cursor: pointer;
  font-size: 0.875rem;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
  flex-shrink: 0;
}

.playback-btn:hover {
  background: var(--surface-hover);
  color: var(--text);
  border-color: var(--accent);
}

.playback-btn.active {
  background: var(--accent);
  color: #0a0e14;
  border-color: var(--accent);
}

.playback-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.playback-step-label {
  flex: 1;
  font-size: 0.75rem;
  color: var(--muted);
  font-family: var(--mono);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.speed-label {
  font-size: 0.75rem;
  color: var(--muted);
  white-space: nowrap;
}

input[type="range"].speed-slider {
  width: 70px;
  accent-color: var(--accent);
  cursor: pointer;
}

/* ------------------------------------------------------------------ */
/* Complexity badge                                                     */
/* ------------------------------------------------------------------ */

.complexity-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-top: 0.75rem;
  padding: 0.5rem 0.85rem;
  background: rgba(61, 156, 245, 0.08);
  border: 1px solid rgba(61, 156, 245, 0.25);
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
  animation: fadeIn 0.3s ease;
}

.complexity-badge[hidden] {
  display: none;
}

.complexity-badge strong {
  color: var(--accent);
}

.complexity-item {
  display: flex;
  gap: 0.35rem;
  align-items: center;
}

.complexity-sep {
  color: var(--border);
}

/* ------------------------------------------------------------------ */
/* Save / Load panel                                                    */
/* ------------------------------------------------------------------ */

.save-load-panel {
  margin-top: 0.75rem;
}

.saved-graph-list {
  list-style: none;
  margin: 0.75rem 0 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.saved-graph-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.6rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  transition: border-color 0.15s;
}

.saved-graph-item:hover {
  border-color: var(--accent);
}

.saved-graph-name {
  flex: 1;
  font-size: 0.8125rem;
  font-family: var(--mono);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.saved-graph-date {
  font-size: 0.7rem;
  color: var(--muted);
  white-space: nowrap;
}

/* ------------------------------------------------------------------ */
/* Context menu                                                         */
/* ------------------------------------------------------------------ */

.canvas-context-menu {
  position: fixed;
  z-index: 9999;
  min-width: 160px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.3rem 0;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
  animation: fadeIn 0.12s ease;
}

.canvas-context-menu[hidden] {
  display: none;
}

.ctx-menu-item {
  display: block;
  width: 100%;
  padding: 0.45rem 0.9rem;
  background: none;
  border: none;
  text-align: left;
  font-family: var(--font);
  font-size: 0.875rem;
  color: var(--text);
  cursor: pointer;
  transition: background 0.1s;
}

.ctx-menu-item:hover {
  background: var(--surface-hover);
}

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

.ctx-menu-sep {
  height: 1px;
  background: var(--border);
  margin: 0.25rem 0;
}

/* ------------------------------------------------------------------ */
/* Inline prompt dialog (node name input on canvas click)              */
/* ------------------------------------------------------------------ */

.canvas-prompt-overlay {
  position: fixed;
  inset: 0;
  z-index: 9998;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  animation: fadeIn 0.15s ease;
}

.canvas-prompt-overlay[hidden] {
  display: none;
}

.canvas-prompt-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem 1.5rem;
  min-width: 280px;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.5);
}

.canvas-prompt-box h3 {
  margin: 0 0 0.75rem;
  font-size: 0.9375rem;
  font-weight: 600;
}

.canvas-prompt-box input[type="text"],
.canvas-prompt-box input[type="number"] {
  margin-bottom: 0.75rem;
}

.canvas-prompt-actions {
  display: flex;
  gap: 0.5rem;
  justify-content: flex-end;
}

/* ------------------------------------------------------------------ */
/* Header                                                               */
/* ------------------------------------------------------------------ */

.site-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
}

.site-header h1 {
  margin: 0 0 0.35rem;
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.lead {
  margin: 0;
  color: var(--muted);
  font-size: 1rem;
}

/* ------------------------------------------------------------------ */
/* Flash messages                                                       */
/* ------------------------------------------------------------------ */

.flash-list {
  list-style: none;
  margin: 0 0 1.25rem;
  padding: 0;
}

.flash-list li {
  padding: 0.65rem 1rem;
  border-radius: var(--radius);
  margin-bottom: 0.5rem;
  font-size: 0.9375rem;
  animation: slideDown 0.2s ease;
}

.flash-list .success {
  background: rgba(52, 199, 89, 0.12);
  border: 1px solid rgba(52, 199, 89, 0.35);
  color: #a8e9b8;
}

.flash-list .error {
  background: rgba(255, 92, 92, 0.1);
  border: 1px solid rgba(255, 92, 92, 0.35);
  color: #ffb3b3;
}

/* ------------------------------------------------------------------ */
/* Layout                                                               */
/* ------------------------------------------------------------------ */

.layout {
  display: grid;
  gap: 1.35rem;
  grid-template-columns: 1fr;
}

.layout-sidebar {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.layout-main .panel {
  padding: 1.4rem 1.5rem;
}

.layout-main .panel h2 {
  font-size: 0.875rem;
}

.layout-main input[type="text"] {
  padding: 0.6rem 0.85rem;
  font-size: 0.9375rem;
}

@media (min-width: 960px) {
  .layout {
    grid-template-columns: minmax(0, 1fr) minmax(380px, 500px);
    align-items: start;
  }

  .layout-sidebar--sticky {
    position: sticky;
    top: 1rem;
    align-self: start;
    max-height: calc(100vh - 2rem);
    overflow-y: auto;
    overflow-x: hidden;
  }
}

/* ------------------------------------------------------------------ */
/* Panel                                                                */
/* ------------------------------------------------------------------ */

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.35rem;
  margin-bottom: 1rem;
}

.panel h2 {
  margin: 0 0 1rem;
  font-size: 0.8125rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.panel--sticky {
  position: sticky;
  top: 1rem;
}

/* ------------------------------------------------------------------ */
/* Mode badge                                                           */
/* ------------------------------------------------------------------ */

.mode-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  font-size: 0.8125rem;
  font-weight: 600;
  background: rgba(61, 156, 245, 0.15);
  color: var(--accent);
  border: 1px solid rgba(61, 156, 245, 0.35);
  margin-bottom: 1rem;
}

.mode-badge.undirected {
  background: rgba(139, 156, 179, 0.12);
  color: var(--muted);
  border-color: var(--border);
}

/* ------------------------------------------------------------------ */
/* Forms                                                                */
/* ------------------------------------------------------------------ */

.form-grid {
  display: grid;
  gap: 0.75rem;
}

label {
  display: block;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--muted);
  margin-bottom: 0.25rem;
}

input[type="text"],
input[type="number"] {
  width: 100%;
  padding: 0.55rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-family: var(--mono);
  font-size: 0.875rem;
  transition: border-color 0.15s, box-shadow 0.15s;
}

input[type="text"]:focus,
input[type="number"]:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(61, 156, 245, 0.2);
}

.radio-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 0.75rem;
}

.radio-row label {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  margin: 0;
  cursor: pointer;
  color: var(--text);
  font-weight: 400;
}

/* ------------------------------------------------------------------ */
/* Buttons                                                              */
/* ------------------------------------------------------------------ */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.55rem 1rem;
  border-radius: 8px;
  border: none;
  font-family: var(--font);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, transform 0.05s, box-shadow 0.15s;
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  background: var(--accent);
  color: #0a0e14;
}

.btn-primary:hover {
  background: var(--accent-dim);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.btn-ghost {
  background: transparent;
  color: var(--muted);
  border: 1px solid var(--border);
}

.btn-ghost:hover {
  background: var(--surface-hover);
  color: var(--text);
}

.btn-danger {
  background: rgba(255, 92, 92, 0.15);
  color: #ff8a8a;
  border: 1px solid rgba(255, 92, 92, 0.4);
}

.btn-danger:hover {
  background: rgba(255, 92, 92, 0.25);
}

.btn-sm {
  padding: 0.3rem 0.6rem;
  font-size: 0.75rem;
  border-radius: 6px;
}

.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.25rem;
}

/* ------------------------------------------------------------------ */
/* Result boxes                                                         */
/* ------------------------------------------------------------------ */

.result-box {
  margin-top: 1rem;
  padding: 0.85rem 1rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 0.8125rem;
  word-break: break-word;
  color: #c5d4e8;
  animation: fadeIn 0.25s ease;
}

.result-box strong {
  color: var(--accent);
  font-weight: 600;
}

.result-box.warning {
  border-color: rgba(245, 166, 35, 0.4);
  background: rgba(245, 166, 35, 0.05);
}

.result-box.warning strong {
  color: var(--warning);
}

/* ------------------------------------------------------------------ */
/* Graph state panel                                                    */
/* ------------------------------------------------------------------ */

.graph-state h2 {
  margin-top: 0;
}

.graph-columns {
  display: grid;
  gap: 1rem;
}

@media (min-width: 360px) {
  .graph-columns {
    grid-template-columns: 1fr 1fr;
  }
}

.pill-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.pill-list li {
  padding: 0.25rem 0.6rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-family: var(--mono);
  font-size: 0.8125rem;
  transition: border-color 0.15s;
}

.pill-list li:hover {
  border-color: var(--accent);
}

.edge-list {
  list-style: none;
  margin: 0;
  padding: 0;
  font-family: var(--mono);
  font-size: 0.8125rem;
}

.edge-list li {
  padding: 0.45rem 0;
  border-bottom: 1px solid var(--border);
  color: var(--muted);
}

.edge-list li:last-child {
  border-bottom: none;
}

.edge-list code {
  color: var(--text);
  font-size: inherit;
}

.empty-hint {
  color: var(--muted);
  font-size: 0.875rem;
  margin: 0;
}

/* ------------------------------------------------------------------ */
/* Footer                                                               */
/* ------------------------------------------------------------------ */

footer.page-footer {
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  font-size: 0.8125rem;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

footer.page-footer a {
  color: var(--muted);
  text-decoration: none;
}

footer.page-footer a:hover {
  color: var(--accent);
}

/* ------------------------------------------------------------------ */
/* Animations                                                           */
/* ------------------------------------------------------------------ */

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

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to   { opacity: 1; transform: translateY(0); }
}