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

:root {
  --bg: #ffffff;
  --fg: #1a1a1a;
  --fg-muted: #6b6b6b;
  --bg-sidebar: #f8f8f8;
  --border: #e5e5e5;
  --sidebar-active-bg: #f0f0f0;
  --sidebar-active-border: #1a1a1a;
  --code-bg: #f5f2eb;
  --code-border: #e5e0d5;
  --accent-hover: #f5f5f5;
  --divider: #d4d4d4;
  --overlay: rgba(0,0,0,0.15);
  --font-bn: 'Noto Serif Bengali', serif;
  --font-en: 'Source Serif 4', Georgia, serif;
  --font-mono: 'JetBrains Mono', monospace;
  --reading-width: 720px;
  --sidebar-width: 280px;
  --header-height: 52px;
}

[data-theme="dark"] {
  --bg: #1a1a2e;
  --fg: #d4d4dc;
  --fg-muted: #8888a0;
  --bg-sidebar: #16162a;
  --border: #2a2a45;
  --sidebar-active-bg: #22223a;
  --sidebar-active-border: #d4d4dc;
  --code-bg: #1e1e35;
  --code-border: #2e2e4a;
  --accent-hover: #22223a;
  --divider: #3a3a55;
  --overlay: rgba(0,0,0,0.4);
}

/* ===== Base ===== */
html { scroll-behavior: smooth; }

body {
  font-family: var(--font-en);
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
  transition: background 0.3s, color 0.3s;
}

a { color: var(--fg-muted); text-decoration: none; transition: color 0.15s; }
a:hover { color: var(--fg); }

/* ===== Header ===== */
.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  border-bottom: 1px solid #e5e5e5;
  background: #fff;
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.site-brand {
  display: flex;
  align-items: center;
  gap: 8px;
}

.site-brand svg {
  color: #333;
  flex-shrink: 0;
}

.site-title {
  font-size: 16px;
  font-weight: 600;
  color: #1a1a1a;
  margin: 0;
  letter-spacing: -0.3px;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 14px;
}

.author-label {
  font-size: 13px;
  color: #8b8b8b;
}

.author-name {
  font-size: 13px;
  color: #0969da;
  font-weight: 500;
  cursor: default;
}

.icon-link {
  color: #656d76;
  text-decoration: none;
  display: flex;
  align-items: center;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  border-radius: 6px;
  transition: color 0.2s, background 0.2s;
}

.icon-link:hover {
  color: #1a1a1a;
  background: #f3f3f3;
}

.menu-btn {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  color: #656d76;
}

/* Dark mode - Header */
[data-theme="dark"] .header {
  background: #161b22;
  border-bottom-color: #30363d;
}

[data-theme="dark"] .site-title {
  color: #e6edf3;
}

[data-theme="dark"] .site-brand svg {
  color: #e6edf3;
}

[data-theme="dark"] .author-label {
  color: #6e7681;
}

[data-theme="dark"] .author-name {
  color: #58a6ff;
}

[data-theme="dark"] .icon-link {
  color: #8b949e;
}

[data-theme="dark"] .icon-link:hover {
  color: #e6edf3;
  background: #21262d;
}

/* ===== Sidebar ===== */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 50;
  transition: transform 0.3s ease;
}

.sidebar-header {
  display: none;
  align-items: center;
  justify-content: space-between;
  padding: 14px 20px;
  border-bottom: 1px solid var(--border);
}
.sidebar-label {
  font-family: var(--font-bn);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fg-muted);
  padding: 20px 20px 12px;
  display: block;
}
.sidebar-close {
  background: none;
  border: none;
  font-size: 18px;
  color: var(--fg-muted);
  cursor: pointer;
}
.sidebar-close:hover { color: var(--fg); }

.sidebar-nav { padding: 4px 0; }

.sidebar-item {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  width: 100%;
  text-align: left;
  padding: 10px 20px;
  border: none;
  background: none;
  cursor: pointer;
  color: var(--fg-muted);
  transition: background 0.15s, color 0.15s;
  border-right: 2px solid transparent;
  font-family: inherit;
}
.sidebar-item:hover {
  background: var(--accent-hover);
  color: var(--fg);
}
.sidebar-item.active {
  background: var(--sidebar-active-bg);
  color: var(--fg);
  border-right-color: var(--sidebar-active-border);
  font-weight: 500;
}

.sidebar-num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--fg-muted);
  margin-top: 3px;
  flex-shrink: 0;
  min-width: 18px;
}
.sidebar-title-bn {
  font-family: var(--font-bn);
  font-size: 0.85rem;
  line-height: 1.4;
}
.sidebar-title-en {
  font-family: var(--font-en);
  font-size: 0.72rem;
  color: var(--fg-muted);
  margin-top: 2px;
}

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: var(--overlay);
  z-index: 40;
}

/* Main wrapper offset for sidebar */
.main-wrapper {
  margin-left: var(--sidebar-width);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ===== Reading area ===== */
.reading-area {
  flex: 1;
  max-width: var(--reading-width);
  margin: 0 auto;
  padding: 40px 24px 0;
  width: 100%;
}

/* Chapter header */
.chapter-header-num {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--fg-muted);
  text-transform: uppercase;
  letter-spacing: 0.12em;
}
.chapter-header-bn {
  font-family: var(--font-bn);
  font-size: 1.75rem;
  font-weight: 600;
  color: var(--fg);
  margin-top: 8px;
  line-height: 1.35;
}
.chapter-header-en {
  font-family: var(--font-en);
  font-size: 1.125rem;
  color: var(--fg-muted);
  font-style: italic;
  margin-top: 4px;
}
.chapter-divider {
  width: 56px;
  height: 1px;
  background: var(--divider);
  margin: 28px 0 32px;
}

/* Reading typography */
.chapter-body {
  font-family: var(--font-bn);
  font-size: 1.1rem;
  line-height: 1.85;
  color: color-mix(in srgb, var(--fg) 88%, transparent);
}

.chapter-body h2 {
  font-family: var(--font-bn);
  font-size: 1.45rem;
  font-weight: 600;
  color: var(--fg);
  margin: 2.5rem 0 1rem;
}
.chapter-body h3 {
  font-family: var(--font-bn);
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--fg);
  margin: 2rem 0 0.75rem;
}
.chapter-body p { margin-bottom: 1.25rem; }

.chapter-body ul, .chapter-body ol {
  margin-bottom: 1.25rem;
  padding-left: 1.5rem;
}
.chapter-body li { margin-bottom: 0.5rem; }

.chapter-body strong { color: var(--fg); }
.chapter-body em { font-style: italic; }

.chapter-body code {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  padding: 0.12em 0.35em;
  border-radius: 4px;
}

.chapter-body pre {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 8px;
  padding: 1.2rem;
  overflow-x: auto;
  margin-bottom: 1.5rem;
  font-size: 0.82rem;
  line-height: 1.6;
}
.chapter-body pre code {
  background: none;
  border: none;
  padding: 0;
}

.chapter-body blockquote {
  border-left: 3px solid var(--divider);
  padding-left: 1.2rem;
  margin-bottom: 1.25rem;
  color: var(--fg-muted);
  font-style: italic;
}

/* ===== Chapter Nav ===== */
.chapter-nav {
  display: flex;
  gap: 16px;
  margin-top: 56px;
  padding: 32px 0;
  border-top: 1px solid var(--border);
}

.nav-btn {
  flex: 1;
  display: block;
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: none;
  cursor: pointer;
  transition: background 0.15s;
  text-decoration: none;
  color: inherit;
}
.nav-btn:hover { background: var(--accent-hover); }
.nav-btn.next { text-align: right; }

.nav-btn-label {
  font-size: 0.75rem;
  color: var(--fg-muted);
  margin-bottom: 4px;
  display: flex;
  align-items: center;
  gap: 4px;
}
.nav-btn.next .nav-btn-label { justify-content: flex-end; }
.nav-btn-title {
  font-family: var(--font-bn);
  font-size: 0.88rem;
  color: var(--fg);
}
.nav-spacer { flex: 1; }

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--border);
  margin-top: 48px;
}
.footer-inner {
  max-width: var(--reading-width);
  margin: 0 auto;
  padding: 36px 24px;
}
.footer-heading {
  font-family: var(--font-en);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--fg);
  margin-bottom: 8px;
}
.footer-links { display: flex; gap: 8px; align-items: center; font-size: 0.85rem; }
.footer-links a { color: var(--fg-muted); }
.footer-links a:hover { color: var(--fg); }
.footer-dot { color: var(--border); }
.footer-section { margin-bottom: 16px; }
.footer-credit {
  font-size: 0.75rem;
  color: var(--fg-muted);
  line-height: 1.6;
  margin-top: 6px;
}
.footer-credit a { text-decoration: underline; }

/* ===== Scrollbar ===== */
.sidebar::-webkit-scrollbar { width: 4px; }
.sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

/* ===== Mobile ===== */
@media (max-width: 1023px) {
  .sidebar {
    transform: translateX(-100%);
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-overlay.open { display: block; }
  .sidebar-header { display: flex; }
  .sidebar-label { padding-top: 8px; }
  .menu-btn { display: flex; }
  .main-wrapper { margin-left: 0; }
  .header { padding: 10px 14px; }
  .site-title { font-size: 14px; }
  .author-name { display: none; }
  .reading-area { padding: 24px 16px 0; }
  .chapter-header-bn { font-size: 1.4rem; }
  .chapter-body { font-size: 1.05rem; }
}

@media (min-width: 1024px) {
  .header { padding: 12px 24px; }
}