/* ── Reset & Variables ─────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg-primary:    #0a0a0f;
  --bg-secondary:  #111118;
  --bg-card:       rgba(255,255,255,0.04);
  --bg-card-hover: rgba(255,255,255,0.08);
  --text-primary:  #e8e8ed;
  --text-secondary:#9999a8;
  --accent:        #4fc3f7;
  --accent-dark:   #0288d1;
  --accent-gradient: linear-gradient(135deg, #4fc3f7, #0288d1);
  --border:        rgba(255,255,255,0.08);
  --green:         #66bb6a;
  --red:           #ef5350;
  --font:          'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --mono:          'Fira Code', 'Cascadia Code', 'Consolas', monospace;
  --transition:    0.3s ease;
  --radius:        12px;
}

html { scroll-behavior: smooth; background: var(--bg-primary); }

body {
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font);
  line-height: 1.6;
  min-height: 100vh;
}

.container { max-width: 1100px; margin: 0 auto; padding: 0 24px; }
.text-secondary { color: var(--text-secondary); }
.accent { color: var(--accent); }
.hidden { display: none !important; }

/* ── Navbar ─────────────────────────────────────────────────────────────── */
.navbar {
  position: fixed; top: 0; left: 0; width: 100%; z-index: 1000;
  padding: 16px 0;
  transition: background var(--transition), padding var(--transition), box-shadow var(--transition);
}
.navbar.scrolled {
  background: rgba(10,10,15,0.95);
  backdrop-filter: blur(20px);
  padding: 10px 0;
  box-shadow: 0 1px 0 var(--border);
}
/* Nav inner: 3-col grid so links sit dead-center on the page */
.nav-inner {
  display: grid; grid-template-columns: 1fr auto 1fr;
  align-items: center; padding: 0 16px;
}
.nav-logo {
  font-size: 1.2rem; font-weight: 700; color: var(--text-primary);
  text-decoration: none; letter-spacing: -0.3px;
}
.nav-logo span { color: var(--accent); }
.nav-links {
  display: flex; gap: 32px; list-style: none; justify-self: center;
}
.nav-links a {
  color: var(--text-secondary); text-decoration: none; font-size: 0.9rem;
  font-weight: 500; transition: color var(--transition);
}
.nav-links a:hover { color: var(--text-primary); }
.nav-toggle {
  display: none; background: none; border: none;
  cursor: pointer; padding: 8px; z-index: 1001;
}
.hamburger {
  display: block; width: 24px; height: 2px;
  background: var(--text-primary); position: relative;
  transition: all var(--transition);
}
.hamburger::before,
.hamburger::after {
  content: ''; position: absolute; left: 0;
  width: 24px; height: 2px; background: var(--text-primary);
  transition: all var(--transition);
}
.hamburger::before { top: -7px; }
.hamburger::after { top: 7px; }
.nav-toggle.active .hamburger { background: transparent; }
.nav-toggle.active .hamburger::before { top: 0; transform: rotate(45deg); }
.nav-toggle.active .hamburger::after { top: 0; transform: rotate(-45deg); }

/* ── Buttons ─────────────────────────────────────────────────────────────── */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 12px 28px; border-radius: 8px; font-weight: 600;
  font-size: 0.95rem; border: none; font-family: var(--font);
  cursor: pointer; text-decoration: none;
  transition: all var(--transition);
}
.btn-primary {
  background: var(--accent-gradient); color: #000;
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(79,195,247,0.3);
}
.btn-outline {
  background: transparent; border: 1px solid var(--accent); color: var(--accent);
}
.btn-outline:hover {
  background: rgba(79,195,247,0.08);
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(79,195,247,0.15);
}
.btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none !important; }
.full-width { width: 100%; justify-content: center; }

/* ── Hero ────────────────────────────────────────────────────────────────── */
#hero {
  min-height: 100vh; display: flex; align-items: center; justify-content: center;
  padding: 120px 24px 80px; position: relative; overflow: hidden;
}
.hero-glow {
  position: absolute; inset: 0; pointer-events: none;
  background: radial-gradient(ellipse at center, rgba(79,195,247,0.06) 0%, transparent 60%);
}
.hero-content {
  text-align: center; position: relative; z-index: 1;
  width: 100%; display: flex; flex-direction: column; align-items: center;
}
.hero-badge {
  display: inline-block; margin-bottom: 24px;
  padding: 6px 18px; border-radius: 20px; font-size: 0.85rem; font-weight: 500;
  background: rgba(79,195,247,0.1); border: 1px solid rgba(79,195,247,0.25);
  color: var(--accent);
}
.hero-content h1 {
  font-size: clamp(2.4rem, 6vw, 4rem); font-weight: 700;
  letter-spacing: -1px; line-height: 1.1; margin-bottom: 20px;
}
.hero-sub {
  max-width: 520px; margin: 0 auto 36px;
  color: var(--text-secondary); font-size: 1.05rem; line-height: 1.7;
}
.hero-actions { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; }

/* ── Sections ────────────────────────────────────────────────────────────── */
.section { padding: 100px 0; }
.section-alt { background: var(--bg-secondary); }
.section-header { text-align: center; margin-bottom: 56px; }
.section-header h2 {
  font-size: clamp(1.6rem, 4vw, 2.4rem); font-weight: 700;
  letter-spacing: -0.5px; margin-bottom: 12px;
}
.section-sub { color: var(--text-secondary); font-size: 1rem; max-width: 500px; margin: 0 auto; }

/* ── Steps Grid ──────────────────────────────────────────────────────────── */
.steps-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 20px;
}
.step-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 28px;
  backdrop-filter: blur(10px); transition: all var(--transition);
}
.step-card:hover { background: var(--bg-card-hover); transform: translateY(-3px); }
.step-icon {
  width: 44px; height: 44px; border-radius: 10px; margin-bottom: 16px;
  display: flex; align-items: center; justify-content: center; font-size: 1.1rem;
  background: rgba(79,195,247,0.12); color: var(--accent);
}
.step-card h3 { font-size: 1rem; font-weight: 600; margin-bottom: 8px; }
.step-card p  { font-size: 0.88rem; color: var(--text-secondary); line-height: 1.6; }

/* ── About Text ──────────────────────────────────────────────────────────── */
.about-text {
  max-width: 720px; margin: 0 auto; display: flex; flex-direction: column; gap: 16px;
  text-align: center;
}
.about-text p { color: var(--text-secondary); font-size: 1rem; line-height: 1.8; }

/* ── Demo Grid (4 equal columns: config + 3 metrics) ────────────────────── */
.demo-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 20px;
  align-items: stretch;
  margin-bottom: 20px;
  transition: all 0.4s ease;
}
/* Before solve: only config card visible → center it */
.demo-grid.solo {
  display: flex; justify-content: center;
}

/* Shared card style */
.demo-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 24px;
  backdrop-filter: blur(10px); text-align: center;
}
.demo-card h3 {
  font-size: 0.9rem; font-weight: 600; margin-bottom: 18px;
  display: flex; align-items: center; justify-content: center; gap: 8px;
  color: var(--text-secondary);
}
.demo-card h3 i { color: var(--accent); }
/* Solo config card width constraint */
.demo-grid.solo .demo-card { width: 380px; }
/* Config card in grid — slightly more padding */
#configCard { padding: 28px 32px; }

/* ── Form ────────────────────────────────────────────────────────────────── */
.form-group { margin-bottom: 16px; }
.form-group label {
  display: block; font-size: 0.78rem; font-weight: 500;
  color: var(--text-secondary); margin-bottom: 6px;
  text-transform: uppercase; letter-spacing: 0.5px;
}
input[type="number"] {
  width: 100%; background: var(--bg-secondary); border: 1px solid var(--border);
  border-radius: 8px; padding: 12px 14px; color: var(--text-primary);
  font-family: var(--mono); font-size: 1rem; outline: none;
  transition: border-color var(--transition);
  appearance: textfield;
  text-align: center;
}
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button { -webkit-appearance: none; }
input[type="number"]:focus { border-color: var(--accent); }

.preset-row { display: flex; gap: 6px; flex-wrap: wrap; justify-content: center; }
.preset-btn {
  background: rgba(79,195,247,0.1); border: 1px solid rgba(79,195,247,0.2);
  color: var(--accent); border-radius: 20px; padding: 4px 12px;
  font-size: 0.78rem; font-weight: 500; cursor: pointer;
  font-family: var(--mono); transition: all var(--transition);
}
.preset-btn:hover, .preset-btn.active {
  background: rgba(79,195,247,0.2); border-color: var(--accent);
}

/* Toggle switch */
.toggle-group { display: flex; align-items: center; justify-content: center; gap: 12px; }
.switch { position: relative; display: inline-block; width: 44px; height: 24px; }
.switch input { opacity: 0; width: 0; height: 0; }
.slider-track {
  position: absolute; cursor: pointer; inset: 0;
  background: rgba(255,255,255,0.1); border-radius: 24px;
  transition: background var(--transition);
}
.slider-track::before {
  content: ''; position: absolute;
  width: 18px; height: 18px; left: 3px; bottom: 3px;
  background: var(--text-secondary); border-radius: 50%;
  transition: all var(--transition);
}
.switch input:checked + .slider-track { background: var(--accent-dark); }
.switch input:checked + .slider-track::before {
  transform: translateX(20px); background: #fff;
}

/* ── Error Box ───────────────────────────────────────────────────────────── */
.error-box {
  margin-top: 14px; padding: 12px 16px; border-radius: var(--radius);
  background: rgba(239,83,80,0.1); border: 1px solid rgba(239,83,80,0.3);
  color: var(--red); font-size: 0.85rem; line-height: 1.5;
}

/* ── Metric cards (cols 2–4 in demo-grid) ───────────────────────────────── */
.metric-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 24px;
  backdrop-filter: blur(10px); transition: all var(--transition);
  display: flex; flex-direction: column; align-items: center; text-align: center;
  justify-content: space-evenly;
}
.metric-card:hover { background: var(--bg-card-hover); }

.metric-algo-name {
  font-size: 0.85rem; font-weight: 600; color: var(--text-secondary);
  text-transform: uppercase; letter-spacing: 0.5px; margin-bottom: 10px;
}

.badge {
  display: inline-block; padding: 2px 10px; border-radius: 20px;
  font-size: 0.72rem; font-weight: 600; white-space: nowrap; flex-shrink: 0;
}
.badge-solved   { background: rgba(102,187,106,0.15); color: var(--green); border: 1px solid rgba(102,187,106,0.3); margin-bottom: 10px; }
.badge-unsolved { background: rgba(239,83,80,0.15);   color: var(--red);   border: 1px solid rgba(239,83,80,0.3); margin-bottom: 10px; }

.metric-stats { display: flex; flex-direction: column; align-items: center; gap: 4px; padding-top: 10px; width: 100%; }
.stat-item { text-align: center; }
.stat-item label {
  display: block; font-size: 0.72rem; color: var(--text-secondary);
  text-transform: uppercase; letter-spacing: 0.4px; margin-bottom: 2px;
}
.stat-item span {
  font-family: var(--mono); font-size: 0.95rem; font-weight: 500; color: var(--text-primary);
}

/* ── Board card (full width below the 4-col row) ────────────────────────── */
.board-card {
  width: 100%; overflow-x: auto; box-sizing: border-box;
}
.board-tabs {
  display: flex; gap: 8px; margin-bottom: 20px; flex-wrap: wrap; justify-content: center;
}
.tab-btn {
  background: rgba(79,195,247,0.08); border: 1px solid rgba(79,195,247,0.15);
  color: var(--text-secondary); border-radius: 20px; padding: 5px 16px;
  font-size: 0.8rem; font-weight: 500; cursor: pointer;
  font-family: var(--font); transition: all var(--transition);
}
.tab-btn:hover, .tab-btn.active {
  background: rgba(79,195,247,0.18); border-color: var(--accent); color: var(--accent);
}
.board-wrapper { display: flex; justify-content: center; width: 100%; overflow-x: auto; }
.board {
  display: inline-grid; border: 1px solid var(--border); border-radius: 8px; overflow: hidden;
  max-width: 100%;
}
.cell {
  display: flex; align-items: center; justify-content: center;
  font-size: 1.2em; user-select: none;
}
.cell.light { background: rgba(255,255,255,0.04); }
.cell.dark  { background: rgba(255,255,255,0.01); }
.cell.queen { background: rgba(79,195,247,0.15); }
.cell.queen::after { content: '♛'; color: var(--accent); font-size: 1.1em; }

.board-unsolved {
  padding: 32px; color: var(--text-secondary); font-size: 0.9rem; text-align: center;
}

/* ── Team ────────────────────────────────────────────────────────────────── */
.section-divider {
  width: 40px; height: 3px; border-radius: 2px;
  background: var(--accent-gradient); margin: 12px auto 0;
}
.team-grid {
  display: flex; justify-content: center; gap: 24px; flex-wrap: wrap;
}
.team-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 36px 48px;
  backdrop-filter: blur(10px); text-align: center;
  transition: all var(--transition);
}
.team-card:hover { background: var(--bg-card-hover); transform: translateY(-3px); }
.team-avatar {
  width: 64px; height: 64px; border-radius: 50%; margin: 0 auto 16px;
  background: var(--accent-gradient); color: #000;
  font-size: 1.2rem; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}
.team-name {
  font-size: 1rem; font-weight: 600; color: var(--text-primary);
}

/* ── Footer ──────────────────────────────────────────────────────────────── */
.footer {
  padding: 36px 0; border-top: 1px solid var(--border);
  background: var(--bg-primary);
}
.footer-inner {
  display: flex; flex-direction: column; align-items: center;
  font-size: 0.85rem; color: var(--text-secondary); gap: 16px;
}
.footer-icons {
  display: flex; gap: 20px;
}
.footer-icons a {
  color: var(--text-secondary); font-size: 1.3rem;
  transition: color var(--transition);
}
.footer-icons a:hover { color: var(--text-primary); }

/* ── Loading spinner ─────────────────────────────────────────────────────── */
.spinner {
  width: 18px; height: 18px; border: 2px solid rgba(0,0,0,0.2);
  border-top-color: #000; border-radius: 50%;
  animation: spin 0.7s linear infinite; display: inline-block;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Responsive ──────────────────────────────────────────────────────────── */
@media (max-width: 900px) {
  .demo-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .nav-inner { display: flex; justify-content: space-between; }
  .nav-links {
    position: fixed; top: 0; right: -100%;
    width: 200px; height: 100vh;
    background: rgba(10,10,15,0.98); backdrop-filter: blur(20px);
    flex-direction: column; justify-content: center; align-items: center;
    gap: 28px; display: flex;
    transition: right var(--transition); z-index: 999;
  }
  .nav-links.open { right: 0; }
  .nav-links li a { font-size: 1rem; padding: 12px 0; display: block; }
  .demo-grid { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
  .hero-actions { flex-direction: column; align-items: center; }
}