/* MathCode Platform — global styles */
:root {
  --bg: #0f1320;
  --bg-soft: #161b2c;
  --bg-card: #1c2238;
  --border: #2a3150;
  --text: #e6e9f5;
  --text-muted: #8a93b8;
  --accent: #7c5cff;
  --accent-2: #4cc9f0;
  --accent-3: #ffb84d;
  --green: #34d399;
  --red: #f87171;
  --tier1: #4cc9f0;
  --tier2: #34d399;
  --tier3: #c792ea;
  --shadow: 0 8px 24px rgba(0,0,0,0.35);
  --radius: 12px;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  min-height: 100vh;
}
a { color: var(--accent-2); text-decoration: none; }
a:hover { text-decoration: underline; }
.muted { color: var(--text-muted); }

/* ---- Top bar ---- */
.topbar {
  display:flex; align-items:center; justify-content:space-between;
  padding: 16px 28px; border-bottom: 1px solid var(--border);
  background: var(--bg-soft);
  position: sticky; top: 0; z-index: 50;
}
.brand {
  display:flex; align-items:center; gap:10px;
  font-weight: 700; font-size: 18px; color: var(--text);
}
.brand-logo {
  width: 32px; height: 32px; border-radius: 8px;
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-2) 100%);
  display:flex; align-items:center; justify-content:center;
  font-weight: 800; font-size: 16px; color: white;
}
.topbar nav { display:flex; gap: 20px; }
.topbar nav a { color: var(--text); font-weight: 500; font-size: 14px; }
.topbar nav a:hover { color: var(--accent-2); }
.topbar-actions { display:flex; gap:10px; align-items:center; }

/* ---- Layout ---- */
.container { max-width: 1180px; margin: 0 auto; padding: 32px 28px; }
.container.narrow { max-width: 720px; }

/* ---- Hero ---- */
.hero {
  padding: 80px 28px 60px;
  text-align: center;
  background: radial-gradient(ellipse at top, rgba(124,92,255,0.18), transparent 60%);
}
.hero h1 {
  font-size: clamp(36px, 5vw, 56px);
  margin: 0 0 16px; font-weight: 800; letter-spacing: -0.02em;
  background: linear-gradient(90deg, #fff 0%, #b8c5ff 100%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p.lead { font-size: 19px; max-width: 720px; margin: 0 auto 28px; color: var(--text-muted); }
.hero-cta { display:flex; gap: 12px; justify-content:center; flex-wrap: wrap; }

/* ---- Buttons ---- */
.btn {
  display:inline-block; padding: 12px 22px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--bg-card);
  color: var(--text); font-size: 14px; font-weight: 600; cursor:pointer;
  text-decoration:none; transition: transform 0.05s, background 0.15s, border-color 0.15s;
}
.btn:hover { background: #232944; border-color: #3a4470; }
.btn:active { transform: translateY(1px); }
.btn.primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border: none; color: white;
}
.btn.primary:hover { filter: brightness(1.08); }
.btn.ghost { background: transparent; }
.btn.danger { background: rgba(248,113,113,0.12); border-color: rgba(248,113,113,0.3); color: var(--red); }
.btn.full { width: 100%; }

/* ---- Sections ---- */
.section { padding: 60px 0; border-top: 1px solid var(--border); }
.section h2 {
  font-size: 28px; margin: 0 0 28px; font-weight: 700;
  letter-spacing: -0.01em;
}
.section h2.center { text-align: center; }

/* ---- Cards ---- */
.cards { display:grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 18px; }
.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px; box-shadow: var(--shadow);
  display:flex; flex-direction:column; gap: 10px;
  transition: transform 0.12s, border-color 0.12s;
}
.card:hover { transform: translateY(-2px); border-color: #3a4470; }
.card h3 { margin: 0; font-size: 18px; }
.card .meta { font-size: 13px; color: var(--text-muted); display:flex; gap:10px; flex-wrap:wrap; }
.card p { margin: 0; font-size: 14px; color: var(--text-muted); }
.card .card-actions { margin-top: auto; display:flex; gap:8px; }

/* ---- Tier pills ---- */
.tier-pill {
  display:inline-block; padding: 3px 10px; border-radius: 999px;
  font-size: 12px; font-weight: 700; letter-spacing: 0.02em;
}
.tier-1 { background: rgba(76,201,240,0.15); color: var(--tier1); }
.tier-2 { background: rgba(52,211,153,0.15); color: var(--tier2); }
.tier-3 { background: rgba(199,146,234,0.15); color: var(--tier3); }
.status-pill {
  display:inline-block; padding: 3px 10px; border-radius: 999px;
  font-size: 12px; font-weight: 600;
}
.status-completed { background: rgba(52,211,153,0.18); color: var(--green); }
.status-in_progress { background: rgba(255,184,77,0.18); color: var(--accent-3); }

/* ---- Forms ---- */
.auth-card {
  max-width: 420px; margin: 80px auto; padding: 32px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow);
}
.auth-card h1 { margin: 0 0 8px; font-size: 24px; }
.auth-card .lead { color: var(--text-muted); margin: 0 0 24px; font-size: 14px; }
.field { display:flex; flex-direction:column; gap:6px; margin-bottom: 14px; }
.field label { font-size: 13px; color: var(--text-muted); font-weight: 600; }
.field input, .field select {
  background: var(--bg); border: 1px solid var(--border);
  color: var(--text); padding: 11px 12px; border-radius: 8px;
  font-size: 14px; font-family: inherit;
}
.field input:focus, .field select:focus { outline: none; border-color: var(--accent); }
.form-msg { font-size: 13px; padding: 8px 12px; border-radius: 8px; margin-bottom: 12px; }
.form-msg.err { background: rgba(248,113,113,0.12); color: var(--red); }
.form-msg.ok { background: rgba(52,211,153,0.12); color: var(--green); }
.auth-foot { text-align:center; margin-top: 16px; font-size: 13px; color: var(--text-muted); }

/* ---- Dashboard ---- */
.stat-row { display:grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 16px; margin-bottom: 28px; }
.stat {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px;
}
.stat .num { font-size: 32px; font-weight: 800; color: var(--text); }
.stat .lbl { font-size: 13px; color: var(--text-muted); margin-top: 4px; text-transform: uppercase; letter-spacing: 0.04em; }
.tier-progress { display:flex; align-items:center; gap: 14px; padding: 14px 0; border-bottom: 1px solid var(--border); }
.tier-progress:last-child { border-bottom: none; }
.bar { flex: 1; height: 8px; background: var(--bg); border-radius: 6px; overflow:hidden; }
.bar-fill { height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2)); transition: width 0.4s; }

/* ---- Table ---- */
table.data { width: 100%; border-collapse: collapse; }
table.data th, table.data td { padding: 12px; text-align: left; border-bottom: 1px solid var(--border); font-size: 14px; }
table.data th { color: var(--text-muted); font-weight: 600; font-size: 12px; text-transform: uppercase; letter-spacing: 0.04em; }
table.data tr:hover td { background: var(--bg-soft); }

/* ---- Learn shell (project iframe view) ---- */
.learn-shell { display:flex; flex-direction:column; height: 100vh; overflow:hidden; }
.learn-bar {
  display:flex; align-items:center; gap: 10px; padding: 8px 12px;
  background: var(--bg-soft); border-bottom: 1px solid var(--border);
  flex-shrink: 0; flex-wrap: wrap;
}
@media (min-width: 769px) { .learn-bar { gap: 18px; padding: 12px 20px; } }
.learn-bar .back { color: var(--text); font-size: 13px; font-weight: 600; }
.learn-title { flex:1; display:flex; align-items:center; gap: 8px; flex-wrap: wrap; min-width: 0; }
.learn-title strong { font-size: 14px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
@media (min-width: 769px) { .learn-title strong { font-size: 15px; } }
.learn-actions { display:flex; gap: 6px; }
.learn-actions .btn { padding: 8px 12px; font-size: 12px; }
.learn-frame { flex: 1; width: 100%; border: none; background: white; }

/* ---- Footer ---- */
footer { padding: 30px 28px; border-top: 1px solid var(--border); color: var(--text-muted); font-size: 13px; text-align: center; }

/* ---- Utility ---- */
.row { display:flex; gap: 14px; align-items:center; flex-wrap: wrap; }
.spacer { flex: 1; }
.center { text-align: center; }
.hide { display: none; }

/* ---- Mobile hamburger toggle ---- */
.mobile-menu-btn {
  display: none;
  background: none; border: none; color: var(--text); cursor: pointer;
  padding: 8px; font-size: 22px; line-height: 1;
}

/* ============================================================
   RESPONSIVE — Tablet (≤ 768px)
   ============================================================ */
@media (max-width: 768px) {
  /* Topbar */
  .topbar { padding: 12px 16px; gap: 8px; }
  .topbar nav { display: none; flex-direction: column; position: absolute;
    top: 100%; left: 0; right: 0; background: var(--bg-soft);
    border-bottom: 1px solid var(--border); padding: 12px 16px; gap: 8px; z-index: 49; }
  .topbar nav.open { display: flex; }
  .topbar nav a { padding: 10px 0; font-size: 16px; border-bottom: 1px solid var(--border); }
  .topbar nav a:last-child { border-bottom: none; }
  .mobile-menu-btn { display: block; }
  .topbar-actions { gap: 6px; }
  .topbar-actions .btn { padding: 8px 14px; font-size: 13px; }

  /* Layout */
  .container { padding: 20px 16px; }

  /* Hero */
  .hero { padding: 48px 16px 36px; }
  .hero p.lead { font-size: 16px; margin-bottom: 20px; }
  .hero-cta { flex-direction: column; align-items: center; }
  .hero-cta .btn { width: 100%; max-width: 320px; text-align: center; }

  /* Cards — stack to single column */
  .cards { grid-template-columns: 1fr; gap: 14px; }
  .card { padding: 16px; }

  /* Sections */
  .section { padding: 36px 0; }
  .section h2 { font-size: 22px; margin-bottom: 20px; }

  /* Stats */
  .stat-row { grid-template-columns: repeat(2, 1fr); gap: 12px; margin-bottom: 20px; }
  .stat { padding: 16px; }
  .stat .num { font-size: 26px; }

  /* Tables — horizontal scroll */
  table.data { display: block; overflow-x: auto; -webkit-overflow-scrolling: touch; }
  table.data th, table.data td { padding: 10px; white-space: nowrap; }

  /* Auth card */
  .auth-card { margin: 40px 16px; padding: 24px; max-width: none; }

  /* Learn shell */
  .learn-bar { padding: 10px 14px; gap: 10px; flex-wrap: wrap; }
  .learn-title strong { font-size: 14px; }
  .learn-actions .btn { padding: 8px 12px; font-size: 13px; }

  /* Footer */
  footer { padding: 24px 16px; }

  /* Buttons — touch-friendly minimum size */
  .btn { min-height: 44px; padding: 12px 18px; }
}

/* ============================================================
   RESPONSIVE — Phone (≤ 480px)
   ============================================================ */
@media (max-width: 480px) {
  .container { padding: 16px 12px; }

  /* Hero */
  .hero { padding: 36px 12px 28px; }
  .hero h1 { font-size: clamp(26px, 7vw, 36px); margin-bottom: 12px; }
  .hero p.lead { font-size: 15px; }

  /* Cards */
  .card h3 { font-size: 16px; }
  .card p { font-size: 13px; }
  .card .meta { font-size: 12px; }

  /* Stats — single column */
  .stat-row { grid-template-columns: 1fr; }
  .stat .num { font-size: 22px; }
  .stat .lbl { font-size: 11px; }

  /* Sections */
  .section h2 { font-size: 20px; }

  /* Auth */
  .auth-card { margin: 24px 8px; padding: 20px 16px; }
  .auth-card h1 { font-size: 20px; }

  /* Topbar */
  .brand { font-size: 16px; gap: 8px; }
  .brand-logo { width: 28px; height: 28px; font-size: 14px; }

  /* Tier pills and status pills */
  .tier-pill, .status-pill { font-size: 11px; padding: 2px 8px; }
}