/* ═══════════════════════════════════════════════════════════
   LLM Stylometry — AI Text Detection
   Design: Technical · Data-science · Editorial
   ═══════════════════════════════════════════════════════════ */

@import url('https://fonts.googleapis.com/css2?family=DM+Sans:opsz,wght@9..40,300;9..40,400;9..40,500;9..40,600;9..40,700&family=JetBrains+Mono:wght@400;500;600&display=swap');

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

:root {
  --bg: #F9F9F8;
  --surface: #FFFFFF;
  --text: #111110;
  --text-secondary: #5F5F5D;
  --text-tertiary: #9E9E9B;
  --accent: #2962D9;
  --accent-light: #EDF0FB;
  --accent-hover: #1B4EC4;
  --border: #E7E7E5;
  --border-light: #F1F1EF;
  --red: #D9382C;
  --red-bg: #FEF4F3;
  --green: #147A40;
  --green-bg: #EDF6F1;
  --amber: #B8740A;
  --amber-bg: #FFFBF3;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.035);
  --shadow: 0 1px 3px rgba(0,0,0,0.05), 0 4px 16px rgba(0,0,0,0.04);
  --shadow-lg: 0 2px 6px rgba(0,0,0,0.04), 0 12px 40px rgba(0,0,0,0.06);
  --radius-sm: 8px;
  --radius: 12px;
  --radius-lg: 16px;
  --font: 'DM Sans', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', 'Fira Code', Consolas, monospace;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

body {
  font-family: var(--font);
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  font-size: 16px;
  font-weight: 400;
  overflow-x: hidden;
}

/* ── Typography ── */
h1, h2, h3, h4 { font-weight: 500; letter-spacing: -0.02em; }
h1 { font-size: clamp(2.6rem, 5.5vw, 4rem); line-height: 1.08; letter-spacing: -0.035em; }
h2 { font-size: clamp(1.8rem, 3.5vw, 2.3rem); line-height: 1.18; }
h3 { font-size: 1.2rem; line-height: 1.3; }
h4 { font-size: 1rem; line-height: 1.4; }
.subtitle { font-size: 1.05rem; color: var(--text-secondary); line-height: 1.65; }
.caption { font-size: 0.8rem; color: var(--text-tertiary); }
.mono { font-family: var(--font-mono); font-size: 0.8rem; }

/* ── Layout ── */
.container { max-width: 1080px; margin: 0 auto; padding: 0 32px; }
.container-narrow { max-width: 700px; margin: 0 auto; padding: 0 32px; }
.section { padding: 100px 0; }

/* ── Nav ── */
.nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(249, 249, 248, 0.8);
  backdrop-filter: blur(18px) saturate(180%);
  -webkit-backdrop-filter: blur(18px) saturate(180%);
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s, background 0.2s;
  padding: 0 32px;
}
.nav.scrolled { border-bottom-color: var(--border); background: rgba(249, 249, 248, 0.94); }
.nav-inner {
  max-width: 1080px; margin: 0 auto; height: 64px;
  display: flex; align-items: center; justify-content: space-between;
}
.nav-brand {
  display: flex; align-items: center; gap: 10px;
  text-decoration: none; color: var(--text);
  font-weight: 600; font-size: 0.95rem; letter-spacing: -0.01em;
}
.nav-brand-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--accent); }
.nav-links { display: flex; gap: 26px; align-items: center; }
.nav-link {
  font-size: 0.85rem; color: var(--text-secondary); text-decoration: none;
  font-weight: 450; transition: color 0.2s; position: relative;
}
.nav-link:hover { color: var(--text); }
.nav-link::after {
  content: ''; position: absolute; bottom: -4px; left: 0; right: 0;
  height: 1.5px; background: var(--accent);
  transform: scaleX(0); transition: transform 0.2s;
}
.nav-link:hover::after, .nav-link.active::after { transform: scaleX(1); }
.nav-link.active { color: var(--text); }
.nav-cta {
  padding: 7px 16px; background: var(--text); color: #fff;
  border-radius: 100px; font-size: 0.8rem; font-weight: 500;
  text-decoration: none; transition: background 0.2s, transform 0.2s;
}
.nav-cta:hover { background: #333; transform: translateY(-1px); }

/* ── Hero ── */
.hero {
  min-height: 100vh;
  display: flex; align-items: center;
  padding: 100px 0 80px;
}
.hero-badge {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 5px 14px; background: var(--accent-light); color: var(--accent);
  border-radius: 100px; font-size: 0.8rem; font-weight: 500; margin-bottom: 24px;
}
.hero-badge-dot { width: 5px; height: 5px; border-radius: 50%; background: var(--accent); animation: pulse 2s ease-in-out infinite; }
@keyframes pulse { 0%,100%{opacity:1} 50%{opacity:0.35} }
.hero-title {
  opacity: 0; transform: translateY(24px);
  animation: fadeUp 700ms var(--ease) forwards;
}
.hero-title em { font-style: normal; color: var(--accent); }
.hero-subtitle {
  margin-top: 18px; max-width: 540px;
  opacity: 0; transform: translateY(24px);
  animation: fadeUp 700ms var(--ease) 100ms forwards;
}
.hero-meta {
  display: flex; gap: 40px; margin-top: 32px;
  opacity: 0; transform: translateY(24px);
  animation: fadeUp 700ms var(--ease) 200ms forwards;
}
.hero-meta-num { font-size: 1.5rem; font-weight: 600; letter-spacing: -0.02em; color: var(--text); }
.hero-meta-label { font-size: 0.8rem; color: var(--text-secondary); margin-top: 1px; }
@keyframes fadeUp { to { opacity: 1; transform: translateY(0); } }

/* ── Detector ── */
.detector-wrap {
  margin-top: 44px;
  opacity: 0; transform: translateY(16px);
  animation: fadeUp 700ms var(--ease) 300ms forwards;
}
.detector-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); box-shadow: var(--shadow); overflow: hidden; position: relative;
}
.detector-card-inner { padding: 28px; }
.detector-card-label {
  display: flex; align-items: center; gap: 8px; margin-bottom: 14px;
  font-size: 0.75rem; font-weight: 600; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--text-tertiary);
}

.detector-textarea {
  width: 100%; min-height: 150px; padding: 18px;
  font-family: var(--font); font-size: 0.9rem; line-height: 1.7;
  color: var(--text); background: var(--bg);
  border: 1px solid var(--border); border-radius: var(--radius);
  resize: vertical; outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.detector-textarea::placeholder { color: var(--text-tertiary); }
.detector-textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(41, 98, 217, 0.08);
}
.detector-textarea.warning {
  border-color: var(--red);
  box-shadow: 0 0 0 3px rgba(217, 56, 44, 0.06);
}

.detector-footer {
  display: flex; align-items: center; justify-content: space-between;
  margin-top: 16px; flex-wrap: wrap; gap: 12px;
}
.detector-wordcount {
  font-size: 0.78rem; color: var(--text-tertiary); font-family: var(--font-mono);
}
.detector-wordcount.warning { color: var(--red); }
.detector-actions { display: flex; align-items: center; gap: 12px; }
.detector-shortcut {
  font-size: 0.72rem; color: var(--text-tertiary);
  padding: 3px 9px; border: 1px solid var(--border);
  border-radius: 4px; font-family: var(--font-mono);
}

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 11px 26px; font-family: var(--font); font-size: 0.9rem; font-weight: 500;
  border: none; border-radius: 100px; cursor: pointer;
  transition: all 0.2s; letter-spacing: -0.01em; white-space: nowrap;
}
.btn-primary { background: var(--text); color: #fff; }
.btn-primary:hover:not(:disabled) { background: #222; transform: translateY(-1px); box-shadow: var(--shadow); }
.btn-primary:disabled { opacity: 0.3; cursor: not-allowed; }
.btn-secondary { background: var(--surface); color: var(--text); border: 1px solid var(--border); }
.btn-secondary:hover { background: var(--bg); border-color: #d0d0ce; }

/* Loading */
.loading-bar {
  position: absolute; top: 0; left: 0; right: 0; height: 2px;
  background: transparent; z-index: 10; transition: background 0.2s;
}
.loading-bar.active {
  background: var(--accent);
  animation: loadBar 1.5s cubic-bezier(0.4,0,0.2,1) infinite;
}
@keyframes loadBar {
  0% { left: -35%; width: 30%; }
  55% { left: 55%; width: 30%; }
  100% { left: 100%; width: 30%; }
}

/* ── Result ── */
.result-panel { max-height: 0; overflow: hidden; transition: max-height 450ms var(--ease); }
.result-panel.visible { max-height: 4000px; }
.result-inner { padding: 0 28px 28px; }
.result-divider { height: 1px; background: var(--border); margin: 0 28px; }
.result-header { display: flex; align-items: center; gap: 16px; margin-bottom: 24px; flex-wrap: wrap; }
.result-badge {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 7px 16px; border-radius: 100px; font-weight: 600; font-size: 0.9rem;
}
.result-badge.ai { background: var(--red-bg); color: var(--red); }
.result-badge.human { background: var(--green-bg); color: var(--green); }
.result-badge-dot { width: 7px; height: 7px; border-radius: 50%; }
.result-badge.ai .result-badge-dot { background: var(--red); }
.result-badge.human .result-badge-dot { background: var(--green); }
.result-confidence { font-size: 0.9rem; color: var(--text-secondary); }
.result-confidence strong { color: var(--text); font-weight: 600; font-size: 1.2rem; }

.result-chart-wrap { max-width: 420px; margin: 0 auto 28px; }
.result-chart-wrap canvas { display: block; }

.result-section-label {
  font-size: 0.72rem; font-weight: 600; letter-spacing: 0.06em;
  text-transform: uppercase; color: var(--text-tertiary); margin-bottom: 14px;
}
.result-features { display: flex; flex-direction: column; gap: 10px; }
.result-feature { display: flex; align-items: center; gap: 14px; }
.result-feature-name {
  width: 145px; font-size: 0.8rem; color: var(--text-secondary);
  text-align: right; flex-shrink: 0;
}
.result-feature-bar-wrap { flex: 1; height: 5px; background: var(--border-light); border-radius: 100px; overflow: hidden; }
.result-feature-bar-fill { height: 100%; background: var(--accent); border-radius: 100px; width: 0; transition: width 700ms var(--ease); }
.result-feature-value { width: 60px; font-size: 0.72rem; font-weight: 500; font-family: var(--font-mono); color: var(--text); }
.result-actions { display: flex; gap: 10px; margin-top: 24px; flex-wrap: wrap; }

.result-ambiguous, .result-error { text-align: center; padding: 32px 24px; border-radius: var(--radius); }
.result-ambiguous {
  background: var(--amber-bg);
  border: 1px solid rgba(184, 116, 10, 0.12);
}
.result-ambiguous p { color: var(--amber); }
.result-error {
  background: var(--red-bg);
  border: 1px solid rgba(217, 56, 44, 0.08);
}
.result-error p { color: var(--red); }

/* ── Methodology ── */
.methodology { background: var(--surface); border-top: 1px solid var(--border); }
.methodology-divider { width: 40px; height: 3px; background: var(--accent); border-radius: 100px; margin: 24px 0; }

/* Steps */
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 40px; }
.step {
  padding: 32px 26px; background: var(--bg);
  border: 1px solid var(--border); border-radius: var(--radius);
  transition: border-color 0.2s, box-shadow 0.2s;
}
.step:hover { border-color: var(--accent); box-shadow: var(--shadow); }
.step-icon {
  width: 40px; height: 40px; border-radius: var(--radius-sm);
  background: var(--accent-light); color: var(--accent);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.1rem; font-weight: 600; margin-bottom: 18px;
}
.step h4 { margin-bottom: 6px; font-weight: 600; }
.step p { font-size: 0.85rem; color: var(--text-secondary); line-height: 1.6; }

/* Charts */
.chart-section { margin-top: 56px; }
.chart-card {
  background: var(--bg); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 28px; margin-top: 20px;
}
.chart-card-header { display: flex; justify-content: space-between; align-items: baseline; margin-bottom: 20px; }
.chart-card h4 { font-size: 0.85rem; font-weight: 500; color: var(--text-secondary); }
.chart-card-badge {
  font-size: 0.7rem; font-weight: 600; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--accent); background: var(--accent-light);
  padding: 3px 10px; border-radius: 100px;
}

/* Validation */
.validation-card {
  margin-top: 56px; text-align: center; padding: 44px 32px;
  background: var(--accent-light); border-radius: var(--radius);
}
.validation-check {
  display: inline-flex; align-items: center; justify-content: center;
  width: 44px; height: 44px; border-radius: 50%;
  background: var(--green-bg); color: var(--green);
  font-size: 1.3rem; font-weight: 700; margin-bottom: 18px;
}
.validation-card p { color: var(--text-secondary); max-width: 520px; margin: 0 auto; }

/* ── Footer ── */
.footer { border-top: 1px solid var(--border); padding: 44px 0; background: var(--surface); }
.footer-inner { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 16px; }
.footer-brand { display: flex; align-items: center; gap: 8px; font-size: 0.85rem; color: var(--text-secondary); }
.footer-links { display: flex; gap: 22px; align-items: center; flex-wrap: wrap; }
.footer-link {
  font-size: 0.8rem; color: var(--text-secondary); text-decoration: none; transition: color 0.2s;
}
.footer-link:hover { color: var(--text); }
.footer-privacy {
  font-size: 0.8rem; color: var(--text-tertiary); text-align: center;
  margin-top: 18px; padding-top: 18px; border-top: 1px solid var(--border-light);
}

/* ── Scroll reveal ── */
.reveal {
  opacity: 0; transform: translateY(24px);
  transition: opacity 550ms var(--ease), transform 550ms var(--ease);
}
.reveal.visible { opacity: 1; transform: translateY(0); }

/* ── Toast ── */
.toast {
  position: fixed; bottom: 32px; left: 50%; transform: translateX(-50%);
  background: var(--text); color: #fff; padding: 10px 24px;
  border-radius: 100px; font-size: 0.85rem; font-weight: 500;
  z-index: 200; opacity: 0; pointer-events: none; transition: opacity 0.2s;
}
.toast.show { opacity: 1; }

/* ── Responsive ── */
@media (max-width: 768px) {
  :root { --radius-lg: 12px; --radius: 10px; }
  body { font-size: 15px; }
  .section { padding: 60px 0; }
  .hero { min-height: auto; padding: 96px 0 48px; }
  .hero-meta { gap: 22px; flex-wrap: wrap; }
  .steps { grid-template-columns: 1fr; }
  .container, .container-narrow { padding: 0 18px; }
  .nav { padding: 0 18px; }
  .nav-links { gap: 14px; }
  .nav-cta { display: none; }
  .detector-card-inner { padding: 20px; }
  .result-inner { padding: 0 20px 20px; }
  .result-divider { margin: 0 20px; }
  .result-feature-name { width: 100px; font-size: 0.73rem; }
  .detector-textarea { min-height: 130px; font-size: 0.85rem; }
  .footer-inner { flex-direction: column; text-align: center; }
  .footer-links { justify-content: center; }
  .chart-card { padding: 20px; }
}