/* ============================================
   Cell Biology Interactive — Layout
   ============================================ */

/* Navigation */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(10, 14, 26, 0.85);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0 var(--space-xl);
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: transform var(--transition-base);
}

.nav--hidden {
  transform: translateY(-100%);
}

.nav__brand {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.nav__brand-icon {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-green));
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
}

.nav__links {
  display: flex;
  gap: var(--space-xs);
  list-style: none;
  overflow-x: auto;
  max-width: 70%;
  scrollbar-width: none;
}

.nav__links::-webkit-scrollbar {
  display: none;
}

.nav__link {
  font-size: 0.8rem;
  color: var(--text-secondary);
  text-decoration: none;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  white-space: nowrap;
  transition: all var(--transition-fast);
  cursor: pointer;
}

.nav__link:hover {
  color: var(--text-primary);
  background: var(--surface-1);
}

.nav__link--active {
  color: var(--accent);
  background: var(--accent-glow);
}

/* Progress bar */
.progress-bar {
  position: fixed;
  top: 60px;
  left: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--accent-green));
  z-index: 999;
  transition: width 100ms linear;
  box-shadow: 0 0 10px var(--accent);
}

/* Main content */
.main {
  padding-top: 60px;
}

/* Section layout */
.section {
  min-height: 100vh;
  padding: var(--space-3xl) var(--space-xl);
  position: relative;
}

.section__header {
  max-width: 800px;
  margin: 0 auto var(--space-2xl);
  text-align: center;
}

.section__number {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: var(--space-sm);
  opacity: 0.8;
}

.section__title {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin-bottom: var(--space-md);
  background: linear-gradient(135deg, var(--text-primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section__subtitle {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.7;
  max-width: 600px;
  margin: 0 auto;
}

/* Canvas container */
.canvas-wrap {
  position: relative;
  width: 100%;
  max-width: 1000px;
  margin: 0 auto;
  background: var(--surface-1);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-subtle);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.canvas-wrap canvas {
  display: block;
  width: 100%;
  height: 500px;
  cursor: crosshair;
}

/* Canvas controls bar */
.canvas-controls {
  display: flex;
  gap: var(--space-xs);
  padding: var(--space-sm) var(--space-md);
  background: var(--surface-2);
  border-top: 1px solid var(--border-subtle);
  flex-wrap: wrap;
}

.canvas-controls__btn {
  font-family: var(--font-body);
  font-size: 0.78rem;
  padding: var(--space-xs) var(--space-md);
  border: 1px solid var(--border-accent);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.canvas-controls__btn:hover {
  background: var(--accent-glow);
  color: var(--text-primary);
}

.canvas-controls__btn--active {
  background: var(--accent);
  color: var(--bg-primary);
  border-color: var(--accent);
  font-weight: 600;
}

/* Info panel */
.info-panel {
  max-width: 1000px;
  margin: var(--space-lg) auto 0;
  padding: var(--space-lg);
  background: var(--surface-1);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-subtle);
  min-height: 80px;
}

.info-panel__title {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: var(--accent);
  margin-bottom: var(--space-sm);
}

.info-panel__text {
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* Grid layouts */
.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
  max-width: 1000px;
  margin: 0 auto;
}

@media (max-width: 768px) {
  .section {
    padding: var(--space-2xl) var(--space-md);
  }
  .grid-2 {
    grid-template-columns: 1fr;
  }
  .nav__links {
    display: none;
  }
  .canvas-wrap canvas {
    height: 350px;
  }
}