:root {
  --bg: #0b0f14;
  --bg-soft: #0f151c;
  --ink: #e6edf3;
  --muted: #9fb0c0;
  --accent: #4d8bff;
  --accent-soft: #1a2f5e;
  --accent-strong: #7aa6ff;
  --accent2: #ff4d5e;
  --accent2-soft: #5e1a2a;
  --line: #1e2733;
  --card: #121a23;
  --glow: rgba(77, 139, 255, 0.15);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background:
    radial-gradient(1200px 600px at 50% -10%, var(--glow), transparent 60%),
    var(--bg);
  color: var(--ink);
  line-height: 1.7;
}

/* Hero */
.hero {
  max-width: 720px;
  margin: 0 auto;
  padding: 88px 24px 56px;
  text-align: center;
}

.hero-kicker {
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 20px;
}

.hero h1 {
  font-size: clamp(2.2rem, 6vw, 3.4rem);
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 20px;
}

.hero h1 span {
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero-text {
  color: var(--muted);
  font-size: 1.1rem;
  max-width: 560px;
  margin: 0 auto 32px;
}

.btn {
  display: inline-block;
  background: var(--accent);
  color: #fff;
  text-decoration: none;
  font-weight: 600;
  padding: 14px 30px;
  border-radius: 999px;
  transition: background 0.2s ease;
}

.btn:hover {
  background: var(--accent-strong);
  box-shadow: 0 6px 24px var(--glow);
}

/* Layout */
main {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 24px 80px;
}

/* TOC */
.toc {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: center;
  margin-bottom: 56px;
}

.toc a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--ink);
  text-decoration: none;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 8px 16px;
  background: var(--card);
  transition: border-color 0.2s, color 0.2s;
}

.toc a:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* Lessons */
.lesson {
  padding: 40px 0;
  border-bottom: 1px solid var(--line);
  scroll-margin-top: 24px;
}

.lesson-num {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 8px;
}

.lesson h2 {
  font-size: clamp(1.5rem, 4vw, 1.9rem);
  letter-spacing: -0.01em;
  margin-bottom: 16px;
}

.lesson p {
  color: var(--muted);
  margin-bottom: 16px;
}

.lesson p:last-child {
  margin-bottom: 0;
}

.lesson strong {
  color: var(--ink);
}

/* Chart */
.chart {
  position: relative;
  height: 240px;
  margin: 28px 0 12px;
  padding: 8px 8px 0;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--card);
  overflow: hidden;
}

.chart::before {
  content: "";
  position: absolute;
  inset: 8px;
  background-image:
    linear-gradient(rgba(230, 237, 243, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(230, 237, 243, 0.06) 1px, transparent 1px);
  background-size: 32px 32px;
}

.chart::after {
  content: "";
  position: absolute;
  left: 8px;
  right: 8px;
  bottom: 8px;
  top: 8px;
}

.chart-path {
  position: absolute;
  bottom: 8px;
  left: 8px;
  right: 8px;
}

.chart .bars {
  position: absolute;
  inset: 8px;
  display: flex;
  align-items: flex-end;
  gap: 3px;
}

.chart .bars span {
  flex: 1;
  background: linear-gradient(to top, rgba(77, 139, 255, 0.16), var(--accent));
  border-radius: 2px 2px 0 0;
  box-shadow: 0 -2px 12px rgba(77, 139, 255, 0.25);
}

.chart .bars span.simple {
  background: linear-gradient(to top, rgba(255, 77, 94, 0.16), var(--accent2));
  box-shadow: 0 -2px 12px rgba(255, 77, 94, 0.25);
}

.chart-axis {
  position: absolute;
  font-size: 0.75rem;
  color: var(--muted);
}

.chart-axis--time {
  right: 14px;
  bottom: 10px;
}

.chart-axis {
  top: 10px;
  left: 14px;
}

.caption {
  font-size: 0.9rem;
  color: var(--muted);
  margin-top: 12px;
}

/* Habits */
.habits {
  list-style: none;
}

.habits li {
  position: relative;
  padding: 14px 0 14px 36px;
  border-bottom: 1px solid var(--line);
  color: var(--muted);
}

.habits li:last-child {
  border-bottom: none;
}

.habits li::before {
  content: "✓";
  position: absolute;
  left: 4px;
  top: 14px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.habits strong {
  color: var(--ink);
}

/* Closing */
.closing {
  padding: 56px 0 0;
  text-align: center;
}

.closing h2 {
  font-size: clamp(1.5rem, 4vw, 1.9rem);
  margin-bottom: 16px;
}

.closing > p {
  color: var(--muted);
  max-width: 560px;
  margin: 0 auto;
}

.disclaimer {
  margin-top: 28px !important;
  font-size: 0.8rem;
  color: var(--muted);
  opacity: 0.8;
  border-top: 1px solid var(--line);
  padding-top: 20px;
}

/* Footer */
.site-footer {
  text-align: center;
  padding: 24px;
  color: var(--muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--line);
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}