* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background: var(--color-bg, #0a0a0f);
  color: var(--color-text, #e0e0e0);
  font-family: var(--font-main, "Segoe UI", system-ui, sans-serif);
  min-height: 100vh;
}

/* ── Hub page ─────────────────────────────── */
.hub {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 2rem;
  background: radial-gradient(ellipse at center, #0d1b2a 0%, #0a0a0f 70%);
}

.hub h1 {
  font-size: clamp(1.8rem, 5vw, 3rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.4rem;
  background: linear-gradient(135deg, #60a5fa, #a78bfa, #34d399);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hub p.subtitle {
  color: var(--color-muted, #6b7280);
  font-size: 1rem;
  margin-bottom: 3rem;
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  width: 100%;
  max-width: 960px;
}

.card {
  background: var(--color-surface, rgba(255, 255, 255, 0.04));
  border: 1px solid var(--color-border, rgba(255, 255, 255, 0.08));
  border-radius: var(--radius-xl, 16px);
  padding: 2rem;
  text-decoration: none;
  color: inherit;
  transition:
    transform 0.2s,
    border-color 0.2s,
    background 0.2s;
  cursor: pointer;
}

.card:hover {
  transform: translateY(-4px);
  border-color: var(--color-border-hover, rgba(96, 165, 250, 0.5));
  background: rgba(96, 165, 250, 0.06);
}

.card .icon {
  font-size: 2.5rem;
  margin-bottom: 0.8rem;
}

.card h2 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.card p {
  font-size: 0.875rem;
  color: var(--color-muted-2, #9ca3af);
  line-height: 1.5;
}

.card .tag {
  display: inline-block;
  margin-top: 1rem;
  padding: 0.2rem 0.6rem;
  background: rgba(96, 165, 250, 0.15);
  color: #60a5fa;
  border-radius: 99px;
  font-size: 0.75rem;
  font-weight: 500;
}

/* ── Simulation pages ─────────────────────── */
.sim-page {
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  background: #000;
  position: relative;
}

canvas {
  display: block;
}

.hud {
  position: absolute;
  top: 16px;
  left: 16px;
  background: rgba(0, 0, 0, 0.55);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg, 12px);
  padding: 12px 16px;
  font-size: 0.8rem;
  line-height: 1.8;
  pointer-events: none;
  min-width: 160px;
}

.hud strong {
  color: var(--color-primary, #60a5fa);
}

.controls-hint {
  position: absolute;
  bottom: 16px;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 99px;
  padding: 8px 20px;
  font-size: 0.78rem;
  color: #9ca3af;
  white-space: nowrap;
}

.back-btn {
  position: absolute;
  top: 16px;
  right: 16px;
  background: rgba(0, 0, 0, 0.55);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-md, 10px);
  padding: 8px 16px;
  color: var(--color-text, #e0e0e0);
  text-decoration: none;
  font-size: 0.82rem;
  transition: border-color 0.2s;
  z-index: 10;
}
.back-btn:hover {
  border-color: rgba(96, 165, 250, 0.6);
  color: var(--color-primary, #60a5fa);
}

.panel {
  position: absolute;
  top: 16px;
  left: 16px;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg, 12px);
  padding: 14px 16px;
  width: 200px;
  font-size: 0.8rem;
  z-index: 10;
}

.panel h3 {
  color: var(--color-primary, #60a5fa);
  margin-bottom: 10px;
  font-size: 0.85rem;
}

.panel label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
  color: var(--color-muted-2, #d1d5db);
}

.panel input[type="range"] {
  width: 90px;
  accent-color: var(--color-primary, #60a5fa);
}

.panel button {
  width: 100%;
  margin-top: 10px;
  padding: 6px;
  background: rgba(96, 165, 250, 0.15);
  border: 1px solid rgba(96, 165, 250, 0.4);
  border-radius: var(--radius-sm, 8px);
  color: var(--color-primary, #60a5fa);
  cursor: pointer;
  font-size: 0.8rem;
  transition: background 0.15s;
}
.panel button:hover {
  background: rgba(96, 165, 250, 0.28);
}

/* ── Simulation description section ──────── */
.sim-description {
  background: linear-gradient(180deg, var(--color-surface, #0d1b2a) 0%, var(--color-bg, #0a0a0f) 100%);
  padding: 3rem 1.5rem;
  min-height: 40vh;
  border-top: 1px solid rgba(96, 165, 250, 0.15);
}
.sim-description-inner {
  max-width: 760px;
  margin: 0 auto;
}
.sim-description h1,
.sim-description h2 {
  font-size: clamp(1.4rem, 3vw, 2rem);
  font-weight: 700;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, #60a5fa, #a78bfa, #34d399);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.sim-description .desc-text {
  font-size: 1.05rem;
  line-height: 1.75;
  color: var(--color-muted-2, #b0b8c8);
  margin-bottom: 1.5rem;
}
.sim-description .desc-details {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}
.sim-description .desc-card {
  background: var(--color-surface, rgba(255, 255, 255, 0.04));
  border: 1px solid var(--color-border, rgba(255, 255, 255, 0.08));
  border-radius: var(--radius-lg, 12px);
  padding: 1.2rem;
}
.sim-description .desc-card h3 {
  color: var(--color-primary, #60a5fa);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
}
.sim-description .desc-card p {
  color: var(--color-muted-2, #9ca3af);
  font-size: 0.88rem;
  line-height: 1.55;
}
.sim-description .scroll-hint {
  position: fixed;
  bottom: 60px;
  right: 20px;
  background: rgba(96, 165, 250, 0.15);
  border: 1px solid rgba(96, 165, 250, 0.3);
  border-radius: var(--radius-full, 99px);
  padding: 8px 16px;
  color: #60a5fa;
  font-size: 0.78rem;
  cursor: pointer;
  z-index: 20;
  animation: bounce-hint 2s ease-in-out infinite;
  text-decoration: none;
}
.sim-description .scroll-hint:hover {
  background: rgba(96, 165, 250, 0.28);
}
@keyframes bounce-hint {
  0%,
  100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-5px);
  }
}