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

/* ===== CSS Variables — Light Mode ===== */
:root {
  --bg: #f6f8fa;
  --surface: #ffffff;
  --border: #d0d7de;
  --text: #24292f;
  --text-muted: #57606a;
  --text-heading: #0969da;
  --nav-bg: #0d1117;
  --nav-text: #58a6ff;
  --code-bg: #f6f8fa;
  --code-border: #d0d7de;
  --table-alt: #f6f8fa;
  --blockquote-border: #0969da;
  --blockquote-bg: #f6f8fa;
  --blockquote-text: #57606a;
  --toggle-bg: #e1e4e8;
  --toggle-knob: #ffffff;
  --toggle-icon: "🌙";
}

/* ===== CSS Variables — Dark Mode ===== */
[data-theme="dark"] {
  --bg: #0d1117;
  --surface: #161b22;
  --border: #30363d;
  --text: #e6edf3;
  --text-muted: #8b949e;
  --text-heading: #58a6ff;
  --nav-bg: #010409;
  --nav-text: #58a6ff;
  --code-bg: #161b22;
  --code-border: #30363d;
  --table-alt: #161b22;
  --blockquote-border: #388bfd;
  --blockquote-bg: #161b22;
  --blockquote-text: #8b949e;
  --toggle-bg: #388bfd;
  --toggle-knob: #ffffff;
  --toggle-icon: "☀️";
}

/* ===== Base ===== */
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background 0.2s, color 0.2s;
}

/* ===== Nav ===== */
nav {
  background: var(--nav-bg);
  padding: 12px 20px;
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

nav a {
  color: var(--nav-text);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  white-space: nowrap;
}

nav a:hover { text-decoration: underline; }

/* ===== Dark Mode Toggle ===== */
.theme-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  user-select: none;
  flex-shrink: 0;
}

.theme-toggle-label {
  color: #8b949e;
  font-size: 0.78rem;
  white-space: nowrap;
}

.toggle-switch {
  position: relative;
  width: 44px;
  height: 24px;
  flex-shrink: 0;
}

.toggle-switch input {
  opacity: 0;
  width: 0;
  height: 0;
  position: absolute;
}

.toggle-track {
  position: absolute;
  inset: 0;
  background: var(--toggle-bg);
  border-radius: 24px;
  transition: background 0.2s;
  cursor: pointer;
}

.toggle-track::after {
  content: '';
  position: absolute;
  top: 3px;
  left: 3px;
  width: 18px;
  height: 18px;
  background: var(--toggle-knob);
  border-radius: 50%;
  transition: transform 0.2s;
}

.toggle-switch input:checked + .toggle-track::after {
  transform: translateX(20px);
}

.toggle-icon {
  font-size: 1rem;
  line-height: 1;
}

/* ===== Main Content ===== */
main {
  max-width: 860px;
  margin: 32px auto;
  padding: 0 20px 60px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  transition: background 0.2s, border-color 0.2s;
}

/* ===== Typography ===== */
main h1 {
  font-size: 1.75rem;
  font-weight: 700;
  padding: 28px 28px 14px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 20px;
  color: var(--text);
}

main h2 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 28px 28px 10px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
  color: var(--text-heading);
}

main h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 20px 28px 8px;
  color: var(--text);
}

main h4 {
  font-size: 0.8rem;
  font-weight: 600;
  margin: 14px 28px 6px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

main p { margin: 8px 28px; color: var(--text); }

main ul, main ol { margin: 8px 28px 8px 52px; }

main li { margin-bottom: 4px; color: var(--text); }

main strong { font-weight: 600; }

main hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 28px;
}

main blockquote {
  border-left: 4px solid var(--blockquote-border);
  margin: 10px 28px;
  padding: 8px 14px;
  background: var(--blockquote-bg);
  color: var(--blockquote-text);
  border-radius: 0 4px 4px 0;
}

/* ===== Code ===== */
main code {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 4px;
  padding: 2px 6px;
  font-family: "SFMono-Regular", Consolas, monospace;
  font-size: 0.85em;
  color: var(--text);
}

main pre {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 6px;
  padding: 14px 28px;
  margin: 10px 28px;
  overflow-x: auto;
}

main pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.88em;
}

/* ===== Tables ===== */
main table {
  width: calc(100% - 56px);
  margin: 10px 28px;
  border-collapse: collapse;
  font-size: 0.88rem;
}

main th {
  background: var(--code-bg);
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
  font-weight: 600;
  color: var(--text);
}

main td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  color: var(--text);
}

main tr:nth-child(even) td { background: var(--table-alt); }

/* ===== Responsive ===== */
@media (max-width: 640px) {
  main {
    margin: 0;
    border-radius: 0;
    border-left: none;
    border-right: none;
  }

  main h1, main h2, main h3, main h4,
  main p, main ul, main ol, main hr,
  main blockquote, main pre, main table {
    margin-left: 14px;
    margin-right: 14px;
  }

  main table { width: calc(100% - 28px); }
  main pre { padding: 12px 14px; }

  .theme-toggle-label { display: none; }
}