:root {
  --navy: #2c3e50;
  --teal: #1abc9c;
  --teal-dark: #0d7a63;
  --gold: #f1c40f;
  --coral: #e74c3c;
  --coral-dark: #c0392b;
  --slate: #556366;
  --white: #ffffff;
  --bg: #f0f4f8;
  --card: #ffffff;
  --border: #dde3ea;
  --gray-100: #f7fafc;
  --gray-200: #edf2f7;
  --gray-300: #e2e8f0;
  --radius: 10px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family:
    'Inter',
    system-ui,
    -apple-system,
    'Segoe UI',
    Roboto,
    Arial,
    sans-serif;
  color: var(--navy);
  background: var(--bg);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
.btn,
.control-label,
.scenario-title,
.guide-toggle {
  font-family: 'Montserrat', system-ui, sans-serif;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--navy);
  color: var(--white);
  padding: 8px 12px;
  z-index: 100;
  border-radius: 0 0 6px 0;
}

.skip-link:focus {
  left: 0;
}

.main-content {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.container {
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
  padding: 24px 20px;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* Header */
.page-header {
  text-align: center;
}

.header-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 12px;
}

.header-left {
  justify-self: start;
}

.header-actions {
  justify-self: end;
}

.page-title {
  margin: 0;
  font-size: clamp(1.4rem, 3vw, 2rem);
  font-weight: 700;
}

.instructions {
  background: rgba(26, 188, 156, 0.1);
  border-left: 4px solid var(--teal);
  border-radius: var(--radius);
  padding: 12px 16px;
}

.instructions p {
  margin: 0;
}

.instructions-how {
  margin-top: 4px !important;
  color: var(--slate);
  font-size: 0.95rem;
}

/* Layout */
.sim-layout {
  display: grid;
  grid-template-columns: 3fr 2fr;
  gap: 20px;
  align-items: start;
}

.panel {
  background: var(--card);
  border-radius: 12px;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
  overflow: hidden;
}

.apparatus-panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 16px;
  gap: 10px;
}

.scenario-banner {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.scenario-count {
  font-size: 0.8rem;
  color: var(--slate);
  background: var(--gray-200);
  border-radius: 999px;
  padding: 2px 10px;
}

.scenario-title {
  font-weight: 700;
  font-size: 1.1rem;
  flex: 1;
}

.motion-tag {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--navy);
  background: rgba(241, 196, 15, 0.25);
  border-radius: 999px;
  padding: 3px 12px;
}

#fbdCanvas {
  width: 100%;
  max-width: 640px;
  height: auto;
  aspect-ratio: 4 / 3;
  border-radius: 8px;
  border: 1px solid var(--border);
  touch-action: none;
  cursor: crosshair;
  background: var(--white);
}

#fbdCanvas:focus-visible {
  outline: 3px solid var(--teal);
  outline-offset: 2px;
}

.canvas-tools {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.9rem;
  color: var(--slate);
}

.toggle {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
}

.controls-panel {
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.control-label {
  font-weight: 700;
  font-size: 0.95rem;
}

.scenario-nav {
  display: flex;
  gap: 8px;
  align-items: center;
}

.scenario-nav select {
  flex: 1;
  min-width: 0;
  font: inherit;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--white);
  color: var(--navy);
}

.scenario-desc {
  margin: 0;
  background: var(--gray-100);
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 0.95rem;
}

.hint {
  margin: 0;
  font-size: 0.85rem;
  color: var(--slate);
}

.keyboard-hint kbd {
  font-family: inherit;
  font-size: 0.75rem;
  background: var(--gray-200);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0 4px;
}

.label-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 6px;
}

.label-btn {
  font: inherit;
  font-size: 0.85rem;
  text-align: left;
  padding: 7px 10px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--white);
  color: var(--navy);
  cursor: pointer;
  transition: all 0.2s ease;
}

.label-btn:hover:not(:disabled) {
  border-color: var(--teal);
  background: rgba(26, 188, 156, 0.08);
}

.label-btn.active {
  background: var(--teal-dark);
  border-color: var(--teal-dark);
  color: var(--white);
}

.label-btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.arrow-actions,
.action-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  border: 1px solid transparent;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 10px 16px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn.small {
  padding: 6px 12px;
  font-size: 0.85rem;
}

.btn:hover:not(:disabled) {
  transform: translateY(-2px);
}

.btn:active:not(:disabled) {
  transform: translateY(1px);
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.teal-btn {
  background: var(--teal-dark);
  color: var(--white);
}

.teal-btn:hover:not(:disabled) {
  background: rgba(13, 122, 99, 0.85);
}

.gold-btn {
  background: rgba(241, 196, 15, 0.8);
  color: var(--navy);
}

.gold-btn:hover:not(:disabled) {
  background: rgba(241, 196, 15, 0.7);
}

.navy-btn {
  background: rgba(44, 62, 80, 0.85);
  color: var(--white);
}

.navy-btn:hover:not(:disabled) {
  background: rgba(44, 62, 80, 0.75);
}

.coral-btn {
  background: var(--coral-dark);
  color: var(--white);
}

.coral-btn:hover:not(:disabled) {
  background: rgba(192, 57, 43, 0.85);
}

.outline-btn {
  background: var(--white);
  color: var(--navy);
  border-color: var(--border);
}

.outline-btn:hover:not(:disabled) {
  border-color: var(--teal);
}

/* Feedback */
.feedback {
  border-radius: var(--radius);
  padding: 14px 16px;
  background: var(--gray-100);
  border: 1px solid var(--border);
  font-size: 0.92rem;
}

.feedback h3 {
  margin: 0 0 8px;
  font-family: 'Montserrat', sans-serif;
  font-size: 1rem;
}

.feedback.success {
  background: rgba(26, 188, 156, 0.1);
  border-color: var(--teal);
}

.feedback ul {
  margin: 0;
  padding-left: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.feedback li {
  padding-left: 22px;
  position: relative;
}

.feedback li::before {
  position: absolute;
  left: 0;
  font-weight: 700;
}

.feedback li.ok::before {
  content: '\2713';
  color: var(--teal-dark);
}

.feedback li.bad::before {
  content: '\2717';
  color: var(--coral-dark);
}

.feedback li.info::before {
  content: '\2022';
  color: var(--slate);
}

.feedback .explain {
  margin: 10px 0 0;
  padding-top: 10px;
  border-top: 1px solid var(--border);
}

/* Guide */
.guide-toggle {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: none;
  border: none;
  padding: 16px 20px;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--navy);
  cursor: pointer;
}

.guide-toggle:hover {
  background: var(--gray-100);
}

.guide-toggle .chevron {
  transition: transform 0.3s ease;
}

.guide-toggle[aria-expanded='true'] .chevron {
  transform: rotate(180deg);
}

.guide-body {
  padding: 0 20px 20px;
}

.guide-body h2 {
  font-size: 1rem;
  margin: 12px 0 8px;
}

.guide-body ol {
  margin: 0;
  padding-left: 20px;
}

.guide-body li {
  margin-bottom: 4px;
}

.force-list {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 6px 16px;
  margin: 0;
}

.force-list dt {
  font-weight: 600;
}

.force-list dd {
  margin: 0;
  color: var(--slate);
}

.site-footer {
  background: var(--navy);
  color: var(--white);
  text-align: center;
  padding: 16px;
  font-size: 0.9rem;
}

.site-footer p {
  margin: 0;
}

@media (max-width: 800px) {
  .sim-layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 540px) {
  .header-grid {
    grid-template-columns: 1fr;
  }

  .header-left,
  .header-actions {
    justify-self: center;
  }

  .container {
    padding: 16px;
  }

  .force-list {
    grid-template-columns: 1fr;
  }

  .force-list dd {
    margin-bottom: 6px;
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
  }
}