:root {
  --purple-900: #2e1065;
  --purple-700: #6d28d9;
  --purple-600: #7c3aed;
  --purple-500: #8b5cf6;
  --purple-300: #c4b5fd;
  --purple-100: #ede9fe;
  --ink: #1a1523;
  --ink-soft: #4b4457;
  --bg: #faf9fc;
  --card: #ffffff;
  --border: #e6e1f0;
  --success: #16a34a;
  --danger: #dc2626;
  --shadow: 0 10px 30px rgba(46, 16, 101, 0.08);
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--ink); }
a { color: var(--purple-700); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: 1180px; margin: 0 auto; padding: 0 24px; }

/* ---------- Nav ---------- */
.navbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 24px; background: rgba(255,255,255,0.9); backdrop-filter: blur(8px);
  position: sticky; top: 0; z-index: 50; border-bottom: 1px solid var(--border);
}
.navbar .brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 1.25rem; color: var(--purple-900); }
.navbar .brand .logo-dot { width: 14px; height: 14px; border-radius: 50%; background: linear-gradient(135deg, var(--purple-500), var(--purple-900)); }
.navbar nav { display: flex; gap: 26px; align-items: center; }
.navbar nav a { color: var(--ink-soft); font-weight: 600; font-size: 0.95rem; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 11px 22px; border-radius: 10px; border: none; font-weight: 700; font-size: 0.95rem;
  cursor: pointer; transition: transform .15s ease, box-shadow .15s ease;
}
.btn-primary { background: linear-gradient(135deg, var(--purple-600), var(--purple-900)); color: #fff; box-shadow: 0 8px 20px rgba(109,40,217,0.35); }
.btn-primary:hover { transform: translateY(-1px); text-decoration: none; }
.btn-ghost { background: transparent; border: 1.5px solid var(--purple-300); color: var(--purple-700); }
.btn-ghost:hover { background: var(--purple-100); text-decoration: none; }
.btn-sm { padding: 7px 14px; font-size: 0.85rem; border-radius: 8px; }

/* ---------- Hero ---------- */
.hero { padding: 90px 24px 70px; text-align: center; background: radial-gradient(circle at 50% -20%, var(--purple-100), transparent 60%); }
.hero .eyebrow { color: var(--purple-700); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; font-size: 0.8rem; }
.hero h1 { font-size: clamp(2.2rem, 5vw, 3.4rem); margin: 14px 0 18px; line-height: 1.15; color: var(--purple-900); }
.hero p.lead { max-width: 640px; margin: 0 auto 34px; color: var(--ink-soft); font-size: 1.15rem; }
.hero .cta-row { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; }
.hero-mock { max-width: 900px; margin: 56px auto 0; border-radius: 20px; box-shadow: var(--shadow); border: 1px solid var(--border); overflow: hidden; background: var(--card); }
.hero-mock .mock-bar { display: flex; gap: 6px; padding: 12px 16px; background: #f3f0fa; border-bottom: 1px solid var(--border); }
.hero-mock .mock-bar span { width: 10px; height: 10px; border-radius: 50%; background: var(--purple-300); }
.hero-mock .mock-body { display: grid; grid-template-columns: 1.2fr 1fr; gap: 0; min-height: 260px; }
.hero-mock .mock-left { padding: 24px; border-right: 1px solid var(--border); font-family: monospace; color: var(--purple-900); }
.hero-mock .mock-right { padding: 24px; color: var(--ink-soft); font-size: 0.95rem; }

/* ---------- Sections ---------- */
.section { padding: 70px 24px; }
.section h2 { font-size: 2rem; text-align: center; color: var(--purple-900); margin-bottom: 10px; }
.section p.sub { text-align: center; color: var(--ink-soft); max-width: 560px; margin: 0 auto 46px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
@media (max-width: 900px) { .grid-3, .grid-4 { grid-template-columns: 1fr; } .hero-mock .mock-body { grid-template-columns: 1fr; } }

.card { background: var(--card); border: 1px solid var(--border); border-radius: 16px; padding: 26px; box-shadow: var(--shadow); }
.card .icon { width: 46px; height: 46px; border-radius: 12px; background: var(--purple-100); display: flex; align-items: center; justify-content: center; font-size: 1.4rem; margin-bottom: 14px; }
.card h3 { margin: 0 0 8px; color: var(--purple-900); }
.card p { margin: 0; color: var(--ink-soft); font-size: 0.95rem; }

footer { padding: 40px 24px; border-top: 1px solid var(--border); text-align: center; color: var(--ink-soft); font-size: 0.85rem; }
footer .legal-links { display: flex; gap: 18px; justify-content: center; margin-top: 12px; flex-wrap: wrap; }

/* ---------- App / Solver page ---------- */
.app-shell { display: flex; flex-direction: column; min-height: 100vh; }
.level-tabs { display: flex; gap: 8px; padding: 14px 24px; overflow-x: auto; border-bottom: 1px solid var(--border); background: #fff; }
.level-tab {
  padding: 9px 18px; border-radius: 999px; border: 1.5px solid var(--border); background: #fff;
  color: var(--ink-soft); font-weight: 700; font-size: 0.88rem; cursor: pointer; white-space: nowrap;
}
.level-tab.active { background: var(--purple-700); border-color: var(--purple-700); color: #fff; }

.solver-input { padding: 18px 24px; display: flex; gap: 12px; border-bottom: 1px solid var(--border); background: #fff; }
.solver-input textarea {
  flex: 1; resize: vertical; min-height: 52px; padding: 12px 14px; border-radius: 10px;
  border: 1.5px solid var(--border); font-size: 1rem; font-family: inherit;
}
.solver-input textarea:focus { outline: none; border-color: var(--purple-500); }

.solver-body { display: grid; grid-template-columns: 1.3fr 1fr; flex: 1; min-height: 0; }
@media (max-width: 920px) { .solver-body { grid-template-columns: 1fr; } }

.monitor-panel { padding: 22px 26px; overflow-y: auto; border-right: 1px solid var(--border); background: #fff; }
.explanation-panel { padding: 22px 26px; overflow-y: auto; background: #fbfaff; }
.panel-title { font-weight: 800; color: var(--purple-900); text-transform: uppercase; font-size: 0.78rem; letter-spacing: .06em; margin-bottom: 16px; }

.step-block { margin-bottom: 22px; padding-bottom: 18px; border-bottom: 1px dashed var(--border); }
.step-block:last-child { border-bottom: none; }
.step-number { display: inline-flex; align-items: center; justify-content: center; width: 26px; height: 26px; border-radius: 50%; background: var(--purple-700); color: #fff; font-size: 0.8rem; font-weight: 800; margin-right: 10px; }
.step-title { font-weight: 700; color: var(--purple-900); }
.step-work { margin: 10px 0; font-size: 1.05rem; }
.step-explanation { color: var(--ink-soft); font-size: 0.93rem; line-height: 1.5; }

.final-answer { margin-top: 8px; padding: 16px; border-radius: 12px; background: var(--purple-100); border: 1px solid var(--purple-300); font-weight: 700; color: var(--purple-900); }
.references { margin-top: 20px; padding: 14px 16px; border-radius: 12px; background: #fff; border: 1px solid var(--border); }
.references h4 { margin: 0 0 8px; font-size: 0.85rem; color: var(--purple-700); }
.references li { font-size: 0.88rem; color: var(--ink-soft); margin-bottom: 6px; }

.toolbar { display: flex; gap: 10px; padding: 12px 24px; border-top: 1px solid var(--border); background: #fff; }
.usage-note { font-size: 0.8rem; color: var(--ink-soft); margin-left: auto; align-self: center; }

/* ---------- Purple dot ---------- */
.purple-dot {
  position: fixed; bottom: 22px; left: 22px; width: 16px; height: 16px; border-radius: 50%;
  background: radial-gradient(circle at 35% 30%, var(--purple-300), var(--purple-900));
  box-shadow: 0 0 0 4px rgba(139, 92, 246, 0.15); cursor: pointer; z-index: 999; border: none;
}
.owner-badge {
  position: fixed; bottom: 22px; left: 48px; background: var(--purple-900); color: #fff;
  font-size: 0.72rem; font-weight: 700; padding: 5px 10px; border-radius: 999px; z-index: 999;
  display: none;
}

/* ---------- Modal ---------- */
.modal-overlay { position: fixed; inset: 0; background: rgba(26,21,35,0.5); display: none; align-items: center; justify-content: center; z-index: 1000; }
.modal-overlay.open { display: flex; }
.modal { background: #fff; border-radius: 16px; padding: 26px; width: 100%; max-width: 360px; box-shadow: var(--shadow); }
.modal h3 { margin-top: 0; color: var(--purple-900); }
.modal input { width: 100%; padding: 10px 12px; border-radius: 8px; border: 1.5px solid var(--border); margin: 10px 0 6px; font-size: 1rem; }
.modal .error-text { color: var(--danger); font-size: 0.85rem; min-height: 18px; }
.modal .modal-actions { display: flex; gap: 10px; margin-top: 12px; }

/* ---------- Pricing ---------- */
.pricing-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; max-width: 1000px; margin: 0 auto; }
@media (max-width: 900px) { .pricing-grid { grid-template-columns: 1fr; } }
.price-card { text-align: center; }
.price-card.featured { border: 2px solid var(--purple-600); transform: scale(1.03); }
.price-card .price { font-size: 2.4rem; font-weight: 800; color: var(--purple-900); margin: 14px 0; }
.price-card .price span { font-size: 1rem; color: var(--ink-soft); font-weight: 500; }
.price-card ul { list-style: none; padding: 0; margin: 20px 0; text-align: left; }
.price-card li { padding: 6px 0; color: var(--ink-soft); font-size: 0.92rem; }
.price-card li::before { content: "✓ "; color: var(--success); font-weight: 700; }

/* ---------- Legal pages ---------- */
.legal-doc { max-width: 780px; margin: 0 auto; padding: 60px 24px 100px; line-height: 1.7; color: var(--ink-soft); }
.legal-doc h1 { color: var(--purple-900); }
.legal-doc h2 { color: var(--purple-900); font-size: 1.2rem; margin-top: 32px; }

/* ---------- Chat widget ---------- */
.chat-fab {
  position: fixed; bottom: 24px; right: 24px; width: 58px; height: 58px; border-radius: 50%;
  background: linear-gradient(135deg, var(--purple-600), var(--purple-900)); color: #fff; border: none;
  font-size: 1.5rem; cursor: pointer; box-shadow: 0 10px 24px rgba(109,40,217,0.4); z-index: 998;
}
.chat-window {
  position: fixed; bottom: 96px; right: 24px; width: 340px; max-width: calc(100vw - 32px); height: 440px;
  background: #fff; border-radius: 16px; box-shadow: var(--shadow); display: none; flex-direction: column;
  overflow: hidden; z-index: 998; border: 1px solid var(--border);
}
.chat-window.open { display: flex; }
.chat-header { background: var(--purple-900); color: #fff; padding: 14px 16px; font-weight: 700; }
.chat-messages { flex: 1; overflow-y: auto; padding: 14px; display: flex; flex-direction: column; gap: 10px; }
.chat-msg { max-width: 85%; padding: 9px 12px; border-radius: 12px; font-size: 0.88rem; line-height: 1.4; }
.chat-msg.user { align-self: flex-end; background: var(--purple-600); color: #fff; }
.chat-msg.bot { align-self: flex-start; background: var(--purple-100); color: var(--ink); }
.chat-input-row { display: flex; border-top: 1px solid var(--border); }
.chat-input-row input { flex: 1; border: none; padding: 12px; font-size: 0.9rem; }
.chat-input-row input:focus { outline: none; }
.chat-input-row button { background: var(--purple-700); color: #fff; border: none; padding: 0 16px; cursor: pointer; }

/* ---------- Print ---------- */
@media print {
  .navbar, .level-tabs, .solver-input, .toolbar, .purple-dot, .owner-badge, .chat-fab, .chat-window, .explanation-panel .panel-title { display: none !important; }
  .solver-body { display: block !important; }
  .monitor-panel, .explanation-panel { border: none !important; padding: 0 !important; }
  body { background: #fff; }
}