/* ===== Reset & Base ===== */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --font-mono: "SF Mono", "Fira Code", Menlo, Consolas, monospace;
  --max-width: 640px;
  --bg: #f5f5f0;
  --bg-secondary: #eaeae5;
  --text: #111111;
  --text-secondary: #555555;
  --border: #999999;
  --code-bg: #e1e1e1;
  --pre-bg: #ffffff;
  --pre-border: #999999;
}

[data-theme="dark"] {
  --bg: #1a1a18;
  --bg-secondary: #222220;
  --text: #e8e8e8;
  --text-secondary: #999999;
  --border: #444444;
  --code-bg: #2a2a28;
  --pre-bg: #111110;
  --pre-border: #444444;
}

html {
  font-size: 16px;
  scrollbar-gutter: stable;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
}

img {
  max-width: 100%;
  display: block;
}

/* ===== Layout ===== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.25rem;
  width: 100%;
}

/* ===== Header ===== */
.header {
  padding: 1rem 0;
}

.header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 0.75rem;
  position: relative;
}

.header .container::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 1.25rem;
  right: 1.25rem;
  height: 1px;
  background: var(--border);
}

.header__logo {
  font-size: 1rem;
  font-weight: 700;
}

.header__nav {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.header__link {
  font-size: 0.8125rem;
  color: var(--text-secondary);
}

.header__link:hover,
.header__link--active {
  color: var(--text);
}

/* ===== Theme Toggle ===== */
.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 0.75rem;
  color: var(--text-secondary);
  padding: 0;
  font-family: inherit;
}

.theme-toggle:hover {
  color: var(--text);
}

/* ===== Main Content ===== */
.main {
  flex: 1;
}

/* ===== Section Title ===== */
.section-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
  padding-bottom: 0.375rem;
  border-bottom: 1px solid var(--border);
}

/* ===== Footer ===== */
.footer {
  padding: 1rem 0;
}

.footer .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 0.75rem;
  position: relative;
}

.footer .container::before {
  content: "";
  position: absolute;
  top: 0;
  left: 1.25rem;
  right: 1.25rem;
  height: 1px;
  background: var(--border);
}

.footer__text {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

.footer__link {
  color: var(--text-secondary);
}

.footer__link:hover {
  color: var(--text);
}

/* ===== Responsive ===== */
/* NOTE: media queries cannot use CSS variables; keep in sync with --max-width */
@media (max-width: 640px) {
  .container {
    padding: 0 1rem;
  }

  .header .container::after {
    left: 1rem;
    right: 1rem;
  }

  .footer .container::before {
    left: 1rem;
    right: 1rem;
  }
}

@media (max-width: 400px) {
  .header__nav {
    gap: 0.75rem;
  }
}