/* ===== Design Tokens ===== */
:root {
  --text-xs:   clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);
  --text-sm:   clamp(0.875rem, 0.8rem + 0.35vw, 1rem);
  --text-base: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);
  --text-lg:   clamp(1.125rem, 1rem + 0.75vw, 1.5rem);
  --text-xl:   clamp(1.5rem, 1.2rem + 1.25vw, 2.25rem);
  --text-2xl:  clamp(2rem, 1.2rem + 2.5vw, 3.5rem);

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;

  --transition-fast: 180ms cubic-bezier(0.16, 1, 0.3, 1);
  --transition-color: 300ms ease;

  --sidebar-width: 280px;

  --font-body: 'Satoshi', 'Inter', sans-serif;
  --font-display: 'General Sans', 'Satoshi', sans-serif;
}

/* ===== Light Mode ===== */
:root, [data-theme="light"] {
  --color-bg: #fafaf9;
  --color-surface: #ffffff;
  --color-surface-2: #f5f5f4;
  --color-border: #e7e5e4;
  --color-border-hover: #d6d3d1;
  --color-text: #1c1917;
  --color-text-muted: #78716c;
  --color-text-faint: #a8a29e;
  --color-primary: #0d9488;
  --color-primary-hover: #0f766e;
  --color-primary-bg: #ccfbf1;
  --color-primary-bg-subtle: #f0fdfa;
  --color-sidebar-bg: #f5f5f4;
  --color-sidebar-hover: #e7e5e4;
  --color-sidebar-active: #ccfbf1;
  --color-sidebar-active-text: #0f766e;
  --color-code-bg: #f5f5f4;
  --color-code-border: #e7e5e4;
  --color-blockquote-border: #0d9488;
  --color-blockquote-bg: #f0fdfa;
  --color-table-head: #f5f5f4;
  --color-table-stripe: #fafaf9;
  --color-table-border: #e7e5e4;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
}

/* ===== Dark Mode ===== */
[data-theme="dark"] {
  --color-bg: #0c0a09;
  --color-surface: #1c1917;
  --color-surface-2: #292524;
  --color-border: #292524;
  --color-border-hover: #44403c;
  --color-text: #e7e5e4;
  --color-text-muted: #a8a29e;
  --color-text-faint: #78716c;
  --color-primary: #2dd4bf;
  --color-primary-hover: #5eead4;
  --color-primary-bg: rgba(45, 212, 191, 0.1);
  --color-primary-bg-subtle: rgba(45, 212, 191, 0.05);
  --color-sidebar-bg: #1c1917;
  --color-sidebar-hover: #292524;
  --color-sidebar-active: rgba(45, 212, 191, 0.1);
  --color-sidebar-active-text: #2dd4bf;
  --color-code-bg: #292524;
  --color-code-border: #44403c;
  --color-blockquote-border: #2dd4bf;
  --color-blockquote-bg: rgba(45, 212, 191, 0.05);
  --color-table-head: #292524;
  --color-table-stripe: #1c1917;
  --color-table-border: #292524;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg: #0c0a09;
    --color-surface: #1c1917;
    --color-surface-2: #292524;
    --color-border: #292524;
    --color-border-hover: #44403c;
    --color-text: #e7e5e4;
    --color-text-muted: #a8a29e;
    --color-text-faint: #78716c;
    --color-primary: #2dd4bf;
    --color-primary-hover: #5eead4;
    --color-primary-bg: rgba(45, 212, 191, 0.1);
    --color-primary-bg-subtle: rgba(45, 212, 191, 0.05);
    --color-sidebar-bg: #1c1917;
    --color-sidebar-hover: #292524;
    --color-sidebar-active: rgba(45, 212, 191, 0.1);
    --color-sidebar-active-text: #2dd4bf;
    --color-code-bg: #292524;
    --color-code-border: #44403c;
    --color-blockquote-border: #2dd4bf;
    --color-blockquote-bg: rgba(45, 212, 191, 0.05);
    --color-table-head: #292524;
    --color-table-stripe: #1c1917;
    --color-table-border: #292524;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  }
}

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

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
  scroll-padding-top: var(--space-16);
}

body {
  min-height: 100dvh;
  line-height: 1.6;
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-color), color var(--transition-color);
  display: flex;
}

a { color: var(--color-primary); text-decoration: none; transition: color var(--transition-fast); }
a:hover { color: var(--color-primary-hover); text-decoration: underline; }

button { cursor: pointer; background: none; border: none; font: inherit; color: inherit; }

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

/* ===== Mobile Header ===== */
.mobile-header {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 56px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-4);
  z-index: 100;
  transition: background-color var(--transition-color);
}

.mobile-title {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: var(--text-sm);
}

/* ===== Sidebar ===== */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100dvh;
  background: var(--color-sidebar-bg);
  border-right: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  z-index: 200;
  transition: background-color var(--transition-color), transform 0.3s ease;
  overflow-y: auto;
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--space-5) var(--space-3);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--color-text);
}

.logo svg { color: var(--color-primary); flex-shrink: 0; }

.theme-toggle {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  transition: background var(--transition-fast), color var(--transition-fast);
}

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

.nav-list {
  flex: 1;
  padding: var(--space-3) var(--space-3);
  overflow-y: auto;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  cursor: pointer;
  transition: all var(--transition-fast);
  margin-bottom: var(--space-1);
  line-height: 1.4;
  width: 100%;
  text-align: left;
}

.nav-item:hover {
  background: var(--color-sidebar-hover);
  color: var(--color-text);
}

.nav-item.active {
  background: var(--color-sidebar-active);
  color: var(--color-sidebar-active-text);
  font-weight: 500;
}

.nav-item svg {
  flex-shrink: 0;
  width: 16px;
  height: 16px;
  opacity: 0.6;
}

.nav-item.active svg { opacity: 1; }

.sidebar-footer {
  padding: var(--space-4) var(--space-5);
  border-top: 1px solid var(--color-border);
  flex-shrink: 0;
}

.sidebar-footer a {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 150;
}

/* ===== Main Content ===== */
.content {
  flex: 1;
  margin-left: var(--sidebar-width);
  min-height: 100dvh;
  transition: margin-left 0.3s ease;
}

.markdown-body {
  max-width: 840px;
  margin: 0 auto;
  padding: var(--space-10) var(--space-8) var(--space-16);
}

/* ===== Welcome Screen ===== */
.welcome {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 60vh;
  text-align: center;
}

.welcome h1 {
  font-family: var(--font-display);
  font-size: var(--text-2xl);
  font-weight: 700;
  margin-bottom: var(--space-4);
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-hover));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.welcome p {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
}

/* ===== Markdown Rendering ===== */
.markdown-body h1 {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 700;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 2px solid var(--color-border);
  line-height: 1.2;
}

.markdown-body h2 {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 600;
  margin-top: var(--space-10);
  margin-bottom: var(--space-4);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--color-border);
  line-height: 1.3;
}

.markdown-body h3 {
  font-family: var(--font-display);
  font-size: var(--text-base);
  font-weight: 600;
  margin-top: var(--space-8);
  margin-bottom: var(--space-3);
}

.markdown-body h4 {
  font-size: var(--text-sm);
  font-weight: 600;
  margin-top: var(--space-6);
  margin-bottom: var(--space-2);
}

.markdown-body p {
  margin-bottom: var(--space-4);
  line-height: 1.7;
  max-width: 72ch;
}

.markdown-body ul, .markdown-body ol {
  margin-bottom: var(--space-4);
  padding-left: var(--space-6);
}

.markdown-body li {
  margin-bottom: var(--space-2);
  line-height: 1.6;
}

.markdown-body li > ul, .markdown-body li > ol {
  margin-top: var(--space-2);
  margin-bottom: 0;
}

.markdown-body strong { font-weight: 600; }

.markdown-body hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: var(--space-8) 0;
}

/* Code */
.markdown-body code {
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-sm);
  padding: 0.15em 0.4em;
  font-size: 0.88em;
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
}

.markdown-body pre {
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  margin-bottom: var(--space-5);
  overflow-x: auto;
  line-height: 1.5;
}

.markdown-body pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: var(--text-sm);
}

/* Blockquote */
.markdown-body blockquote {
  border-left: 3px solid var(--color-blockquote-border);
  background: var(--color-blockquote-bg);
  padding: var(--space-4) var(--space-5);
  margin-bottom: var(--space-4);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  color: var(--color-text-muted);
}

.markdown-body blockquote p:last-child { margin-bottom: 0; }

/* Table */
.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: var(--space-5);
  font-size: var(--text-sm);
  border: 1px solid var(--color-table-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.markdown-body .table-wrapper {
  overflow-x: auto;
  margin-bottom: var(--space-5);
  border-radius: var(--radius-md);
}

.markdown-body .table-wrapper table {
  margin-bottom: 0;
}

.markdown-body thead th {
  background: var(--color-table-head);
  font-weight: 600;
  text-align: left;
  padding: var(--space-3) var(--space-4);
  border-bottom: 2px solid var(--color-table-border);
  white-space: nowrap;
}

.markdown-body tbody td {
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-table-border);
  vertical-align: top;
}

.markdown-body tbody tr:nth-child(even) {
  background: var(--color-table-stripe);
}

/* Links in markdown */
.markdown-body a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.markdown-body a:hover {
  color: var(--color-primary-hover);
}

/* ===== Scroll to Top ===== */
.scroll-top {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--color-primary);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
  z-index: 50;
}

.scroll-top.visible {
  opacity: 1;
  pointer-events: auto;
}

.scroll-top:hover { transform: translateY(-2px); }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .mobile-header { display: flex; }
  .desktop-only { display: none; }

  .sidebar {
    transform: translateX(-100%);
  }

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

  .sidebar-overlay.open {
    display: block;
  }

  .content {
    margin-left: 0;
    padding-top: 56px;
  }

  .markdown-body {
    padding: var(--space-6) var(--space-5) var(--space-12);
  }

  .markdown-body table {
    font-size: var(--text-xs);
  }

  .markdown-body thead th,
  .markdown-body tbody td {
    padding: var(--space-2) var(--space-3);
  }
}

/* ===== Loading State ===== */
.loading {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 40vh;
  color: var(--color-text-muted);
  font-size: var(--text-lg);
}

.loading::after {
  content: '';
  display: inline-block;
  width: 20px;
  height: 20px;
  margin-left: var(--space-3);
  border: 2px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ===== Selection ===== */
::selection {
  background: var(--color-primary-bg);
  color: var(--color-text);
}

/* ===== Focus ===== */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ===== Smooth Theme Transitions ===== */
.sidebar, .mobile-header, .content, .markdown-body,
.nav-item, .sidebar-footer, .sidebar-header {
  transition: background-color var(--transition-color),
              border-color var(--transition-color),
              color var(--transition-color);
}