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

:root {
  --bg: #fff;
  --bg-2: #f8f8f8;
  --text: #111;
  --text-2: #444;
  --text-3: #888;
  --border: #e5e5e5;
  --accent: #2563eb;
  --font: system-ui, -apple-system, sans-serif;
}

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

nav {
  padding: 20px 40px;
  border-bottom: 1px solid var(--border);
}
nav a {
  font-size: 0.8125rem;
  color: var(--text-3);
  text-decoration: none;
}
nav a:hover { color: var(--text); }

main {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 40px 80px;
}

/* Hero */
.hero {
  padding: 80px 0 72px;
  border-bottom: 1px solid var(--border);
}
.label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 24px;
}
h1 {
  font-size: 3.5rem;
  line-height: 1.08;
  letter-spacing: -0.04em;
  margin-bottom: 24px;
}
.line { display: block; }
.accent { color: var(--accent); }
.sub {
  font-size: 1.0625rem;
  color: var(--text-2);
  max-width: 560px;
  line-height: 1.7;
  margin-bottom: 36px;
}
.actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}
.btn-primary {
  display: inline-block;
  padding: 11px 24px;
  background: var(--accent);
  color: #fff;
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: 6px;
  transition: background 0.15s;
}
.btn-primary:hover { background: #1d4ed8; }
.btn-ghost {
  display: inline-block;
  padding: 11px 24px;
  color: var(--text-2);
  text-decoration: none;
  font-size: 0.9rem;
  border-radius: 6px;
  border: 1px solid var(--border);
  transition: border-color 0.15s, color 0.15s;
}
.btn-ghost:hover { border-color: #bbb; color: var(--text); }

/* Loop section */
.loop {
  padding: 64px 0;
  border-bottom: 1px solid var(--border);
}
h2 {
  font-size: 1.375rem;
  letter-spacing: -0.02em;
  margin-bottom: 36px;
}
.steps {
  display: grid;
  gap: 0;
}
.step {
  display: flex;
  gap: 24px;
  align-items: flex-start;
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
}
.step:last-child { border-bottom: none; }
.step-num {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  color: var(--text-3);
  font-family: monospace;
  flex-shrink: 0;
  width: 28px;
  padding-top: 2px;
}
.step-name {
  font-weight: 600;
  font-size: 0.9375rem;
  margin-bottom: 4px;
}
.step-desc {
  font-size: 0.875rem;
  color: var(--text-2);
  line-height: 1.6;
}

/* Compare section */
.contrast {
  padding: 64px 0 0;
}
.compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  margin-top: 0;
}
.compare-col {
  padding: 28px;
  border-radius: 10px;
  border: 1px solid var(--border);
}
.compare-col.before { background: var(--bg-2); }
.compare-col.after { background: #eff6ff; border-color: #bfdbfe; }
.compare-label {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 16px;
}
.compare-col.after .compare-label { color: var(--accent); }
.compare-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.compare-list li {
  font-size: 0.875rem;
  color: var(--text-2);
  padding-left: 18px;
  position: relative;
}
.before .compare-list li::before {
  content: '·';
  position: absolute;
  left: 0;
  color: var(--text-3);
}
.after .compare-list li::before {
  content: '✓';
  position: absolute;
  left: 0;
  color: var(--accent);
  font-size: 0.75rem;
  top: 1px;
}

@media (max-width: 640px) {
  nav { padding: 16px 20px; }
  main { padding: 0 20px 60px; }
  h1 { font-size: 2.25rem; }
  .compare { grid-template-columns: 1fr; }
}