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

:root {
  --c-bg: #ffffff;
  --c-bg-soft: #f6f8fa;
  --c-bg-sidebar: #f0f2f5;
  --c-text: #1a1a2e;
  --c-text-secondary: #5c6370;
  --c-text-muted: #8b95a5;
  --c-border: #e2e6ea;
  --c-accent: #5b6cf7;
  --c-accent-soft: rgba(91, 108, 247, 0.08);
  --c-accent-hover: #4a5ae6;
  --c-code-bg: #f4f5f7;
  --c-link: #5b6cf7;
  --sidebar-w: 260px;
  --font-body: "Roboto", sans-serif;
  --font-heading: "Roboto Slab", serif;
  --font-mono: "Fira Code", monospace;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  color: var(--c-text);
  background: var(--c-bg);
  line-height: 1.7;
  display: flex;
  min-height: 100vh;
}

/* ---- Sidebar ---- */

.sidebar {
  width: var(--sidebar-w);
  min-width: var(--sidebar-w);
  padding: 1.6rem 1.2rem;
  border-right: 1px solid var(--c-border);
  background: var(--c-bg-sidebar);
  overflow-y: auto;
  position: sticky;
  top: 0;
  height: 100vh;
}

.sidebar .home-link {
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 700;
  color: var(--c-text);
  text-decoration: none;
  letter-spacing: -0.01em;
}

.sidebar h4 {
  margin-top: 1.4rem;
  margin-bottom: 0.35rem;
  font-family: var(--font-body);
  font-size: 0.65rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--c-text-muted);
}

.sidebar ul {
  list-style: none;
}

.sidebar li {
  margin: 1px 0;
}

.sidebar a {
  display: block;
  padding: 0.25rem 0.6rem;
  border-radius: 6px;
  font-size: 0.82rem;
  color: var(--c-text-secondary);
  text-decoration: none;
  transition:
    background 0.15s,
    color 0.15s;
}

.sidebar a:hover {
  background: var(--c-accent-soft);
  color: var(--c-accent);
}

.sidebar a.current {
  background: var(--c-accent-soft);
  color: var(--c-accent);
  font-weight: 500;
}

/* ---- Main content ---- */

.main-content {
  flex: 1;
  min-width: 0;
  max-width: 48rem;
  margin: 0 auto;
  padding: 2.5rem 3rem;
}

.main-content img {
  display: block;
  max-width: calc(100% + 4rem);
  margin-left: -2rem;
  margin-right: -2rem;
  margin-top: 1.2rem;
  margin-bottom: 1.2rem;
  height: auto;
  border-radius: 8px;
  border: 1px solid var(--c-border);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

/* ---- Typography ---- */

.main-content h1,
.main-content h2,
.main-content h3,
.main-content h4 {
  font-family: var(--font-heading);
  color: var(--c-text);
  line-height: 1.3;
  margin-top: 2rem;
  margin-bottom: 0.6rem;
}

.main-content h1 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-top: 0;
  padding-bottom: 0.6rem;
  border-bottom: 1px solid var(--c-border);
}

.main-content h2 {
  font-size: 1.3rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--c-border);
}

.main-content h3 {
  font-size: 1.05rem;
  font-weight: 600;
}

.main-content h4 {
  font-size: 0.92rem;
  font-weight: 600;
}

.main-content p {
  margin-bottom: 1rem;
}

.main-content a {
  color: var(--c-link);
  text-decoration: none;
  font-weight: 500;
}

.main-content a:hover {
  text-decoration: underline;
}

/* ---- Lists ---- */

.main-content ul,
.main-content ol {
  margin-bottom: 1rem;
  padding-left: 1.5rem;
}

.main-content li {
  margin-bottom: 0.3rem;
}

.main-content li > ul,
.main-content li > ol {
  margin-top: 0.3rem;
  margin-bottom: 0;
}

/* ---- Code ---- */

.main-content code {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  background: var(--c-code-bg);
  padding: 0.15em 0.4em;
  border-radius: 4px;
}

.main-content pre {
  background: var(--c-bg-soft);
  border: 1px solid var(--c-border);
  border-radius: 8px;
  padding: 1rem 1.2rem;
  overflow-x: auto;
  margin-bottom: 1rem;
  line-height: 1.55;
}

.main-content pre code {
  background: none;
  padding: 0;
  font-size: 0.8rem;
}

/* ---- Blockquote ---- */

.main-content blockquote {
  margin: 0 0 1rem;
  padding: 0.6rem 1rem;
  border-left: 3px solid var(--c-accent);
  background: var(--c-accent-soft);
  border-radius: 0 6px 6px 0;
  color: var(--c-text-secondary);
}

.main-content blockquote p:last-child {
  margin-bottom: 0;
}

/* ---- Tables ---- */

.main-content table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1rem;
  font-size: 0.88rem;
}

.main-content th,
.main-content td {
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--c-border);
  text-align: left;
}

.main-content th {
  background: var(--c-bg-soft);
  font-weight: 600;
}

.main-content tr:nth-child(even) {
  background: var(--c-bg-soft);
}

/* ---- Horizontal rule ---- */

.main-content hr {
  border: none;
  border-top: 1px solid var(--c-border);
  margin: 2rem 0;
}

/* ---- Index cards ---- */

.index-card {
  margin-bottom: 0.75rem;
  padding: 1rem 1.2rem;
  border: 1px solid var(--c-border);
  border-radius: 8px;
  transition:
    border-color 0.15s,
    box-shadow 0.15s;
}

.index-card:hover {
  border-color: var(--c-accent);
  box-shadow: 0 2px 12px rgba(91, 108, 247, 0.08);
}

.index-card h3 {
  margin: 0 0 0.25rem;
  font-size: 0.95rem;
  border: none;
  padding: 0;
}

.index-card p {
  margin: 0;
  font-size: 0.85rem;
  color: var(--c-text-secondary);
}

/* ---- Hamburger (mobile) ---- */

.hamburger {
  display: none;
  position: fixed;
  top: 0.75rem;
  left: 0.75rem;
  z-index: 1001;
  background: var(--c-accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 1.2rem;
  width: 2.2rem;
  height: 2.2rem;
  cursor: pointer;
  line-height: 1;
  transition: background 0.15s;
}

.hamburger:hover {
  background: var(--c-accent-hover);
}

@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    z-index: 1000;
    height: 100%;
    transform: translateX(-100%);
    transition: transform 0.2s ease;
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .hamburger {
    display: block;
  }

  .main-content {
    padding: 3.5rem 1.2rem 2rem;
  }
}