:root {
  color-scheme: light;
  --fc-bg: #f4f6fb;
  --fc-card-bg: #ffffff;
  --fc-text: #1c2333;
  --fc-muted: #5b6478;
  --fc-border: #e1e5ee;
  --fc-accent: #3b6fd6;
  --fc-accent-soft: #e8effc;
  --fc-elementary: #1c9d7c;
  --fc-middle: #6151d3;
  --fc-high: #0e7490;
  --fc-plot-bg: #ffffff;
  font-family: 'Segoe UI', system-ui, -apple-system, Roboto, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--fc-bg);
  color: var(--fc-text);
}

.fc-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
  background: var(--fc-card-bg);
  border-bottom: 1px solid var(--fc-border);
}

.fc-brand {
  display: flex;
  align-items: baseline;
  gap: 8px;
}

.fc-brand-mark {
  font-size: 22px;
  font-weight: 800;
  color: var(--fc-accent);
}

.fc-brand-tagline {
  font-size: 13px;
  color: var(--fc-muted);
}

.fc-layout {
  display: flex;
  min-height: calc(100vh - 60px);
  max-width: 1200px;
  margin: 0 auto;
}

.fc-sidebar {
  width: 220px;
  flex-shrink: 0;
  padding: 20px 12px;
  border-right: 1px solid var(--fc-border);
}

.fc-nav-group {
  margin-bottom: 18px;
}

.fc-nav-heading {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--fc-muted);
  padding: 4px 10px;
}

.fc-nav-btn {
  display: block;
  width: 100%;
  text-align: left;
  padding: 9px 10px;
  margin: 2px 0;
  border: none;
  background: transparent;
  border-radius: 8px;
  font-size: 14px;
  color: var(--fc-text);
  cursor: pointer;
}

.fc-nav-btn:hover { background: var(--fc-accent-soft); }
.fc-nav-btn.active { background: var(--fc-accent); color: #fff; font-weight: 600; }

.fc-main {
  flex: 1;
  min-width: 0;
  padding: 24px 32px 60px;
}

.fc-current-title {
  margin: 0 0 2px;
  font-size: 26px;
}

.fc-current-tagline {
  color: var(--fc-muted);
  margin: 0 0 20px;
  font-size: 14px;
}

.fc-card {
  background: var(--fc-card-bg);
  border: 1px solid var(--fc-border);
  border-radius: 12px;
  padding: 18px 20px;
  margin-bottom: 16px;
}

.fc-card h3 {
  margin-top: 0;
  font-size: 15px;
  color: var(--fc-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.fc-row {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  align-items: flex-end;
}

.fc-field {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 13px;
  color: var(--fc-muted);
}

.fc-field-label { font-weight: 600; }

.fc-input {
  padding: 9px 10px;
  border: 1px solid var(--fc-border);
  border-radius: 8px;
  font-size: 15px;
  min-width: 90px;
  background: #fff;
  color: var(--fc-text);
}

.fc-input:focus {
  outline: none;
  border-color: var(--fc-accent);
  box-shadow: 0 0 0 3px var(--fc-accent-soft);
}

.fc-btn {
  padding: 9px 16px;
  border: none;
  border-radius: 8px;
  background: var(--fc-accent);
  color: #fff;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
}
.fc-btn:hover { filter: brightness(1.08); }
.fc-btn.secondary { background: var(--fc-accent-soft); color: var(--fc-accent); }

.fc-keypad {
  display: grid;
  grid-template-columns: repeat(4, 56px);
  gap: 8px;
  margin: 12px 0;
}
.fc-key {
  padding: 14px 0;
  border: 1px solid var(--fc-border);
  border-radius: 10px;
  background: #fff;
  font-size: 18px;
  font-weight: 700;
  cursor: pointer;
}
.fc-key:hover { background: var(--fc-accent-soft); }
.fc-key.op { background: var(--fc-accent); color: #fff; border-color: var(--fc-accent); }

.fc-result {
  font-size: 22px;
  font-weight: 700;
  padding: 14px 16px;
  background: var(--fc-accent-soft);
  border-radius: 10px;
  color: var(--fc-accent);
  margin-top: 10px;
}

.fc-steps {
  margin-top: 12px;
  font-size: 14px;
  color: var(--fc-muted);
}
.fc-step { padding: 3px 0; }

.fc-error {
  padding: 12px 14px;
  background: #fdeceb;
  color: #a8321d;
  border-radius: 8px;
}

.fc-plot {
  border: 1px solid var(--fc-border);
  border-radius: 10px;
  max-width: 100%;
  margin-top: 10px;
}

.fc-visual-dots {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin: 10px 0;
}
.fc-dot {
  width: 18px; height: 18px;
  border-radius: 50%;
  background: var(--fc-accent);
}
.fc-dot.neg { background: var(--fc-high); }

.fc-array-grid {
  display: grid;
  gap: 4px;
  margin: 12px 0;
}
.fc-array-cell {
  width: 20px; height: 20px;
  border-radius: 4px;
  background: var(--fc-accent);
}

/* Section accent colors */
body[data-active-section="elementary"] .fc-nav-btn.active,
body[data-active-section="elementary"] .fc-btn { background: var(--fc-elementary); }
body[data-active-section="elementary"] .fc-input:focus { border-color: var(--fc-elementary); box-shadow: 0 0 0 3px #e4f5f0; }
body[data-active-section="elementary"] .fc-result { color: var(--fc-elementary); background: #e4f5f0; }
body[data-active-section="elementary"] .fc-brand-mark { color: var(--fc-elementary); }

body[data-active-section="middle-school"] .fc-nav-btn.active,
body[data-active-section="middle-school"] .fc-btn { background: var(--fc-middle); }
body[data-active-section="middle-school"] .fc-input:focus { border-color: var(--fc-middle); box-shadow: 0 0 0 3px #ece9fb; }
body[data-active-section="middle-school"] .fc-result { color: var(--fc-middle); background: #ece9fb; }
body[data-active-section="middle-school"] .fc-brand-mark { color: var(--fc-middle); }

body[data-active-section="high-school"] .fc-nav-btn.active,
body[data-active-section="high-school"] .fc-btn { background: var(--fc-high); }
body[data-active-section="high-school"] .fc-input:focus { border-color: var(--fc-high); box-shadow: 0 0 0 3px #e0f2f4; }
body[data-active-section="high-school"] .fc-result { color: var(--fc-high); background: #e0f2f4; }
body[data-active-section="high-school"] .fc-brand-mark { color: var(--fc-high); }

@media (max-width: 760px) {
  .fc-layout { flex-direction: column; }
  .fc-sidebar {
    width: auto;
    border-right: none;
    border-bottom: 1px solid var(--fc-border);
    display: flex;
    overflow-x: auto;
    padding: 12px;
  }
  .fc-nav-group { margin-bottom: 0; margin-right: 14px; }
  .fc-main { padding: 18px; }
  .fc-keypad { grid-template-columns: repeat(4, 1fr); }
}