/* ===== DESIGN TOKENS ===== */
:root {
  /* Type Scale */
  --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);
  --text-3xl:  clamp(2.5rem,   1rem    + 4vw,    5rem);

  /* Spacing */
  --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;
  --space-32: 8rem;

  /* Fonts */
  --font-display: 'Cabinet Grotesk', 'Inter', sans-serif;
  --font-body: 'Satoshi', 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Transitions */
  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);
}

/* ===== LIGHT MODE ===== */
:root, [data-theme="light"] {
  --color-bg:          #F5F3EE;
  --color-surface:     #FAFAF8;
  --color-surface-2:   #FFFFFF;
  --color-border:      #DDD9D1;
  --color-divider:     #E8E5DF;
  --color-text:        #1A1814;
  --color-text-muted:  #6B6860;
  --color-text-faint:  #A8A59E;
  --color-primary:     #1B6B5A;
  --color-primary-hover: #145544;
  --color-primary-light: #E8F5F0;
  --color-accent:      #D97706;
  --color-accent-light: #FEF3C7;
  --color-code-bg:     #1E1E2E;
  --color-code-text:   #CDD6F4;
  --color-code-comment:#6C7086;
  --color-code-keyword:#CBA6F7;
  --color-code-string: #A6E3A1;
  --color-code-number: #FAB387;
  --color-code-func:   #89B4FA;
  --color-code-class:  #F9E2AF;
  --color-code-builtin:#F38BA8;
  --color-code-op:     #89DCEB;
  --color-success:     #22863A;
  --color-error:       #CB2431;
  --color-output-bg:   #F0EDE7;
  --color-output-text: #1A1814;

  --shadow-sm: 0 1px 2px oklch(0.2 0.01 80 / 0.06);
  --shadow-md: 0 4px 12px oklch(0.2 0.01 80 / 0.08);
  --shadow-lg: 0 12px 32px oklch(0.2 0.01 80 / 0.12);
}

/* ===== DARK MODE ===== */
[data-theme="dark"] {
  --color-bg:          #111111;
  --color-surface:     #1A1A1A;
  --color-surface-2:   #222222;
  --color-border:      #333333;
  --color-divider:     #2A2A2A;
  --color-text:        #E0DED8;
  --color-text-muted:  #8A8880;
  --color-text-faint:  #5A5850;
  --color-primary:     #5BB89A;
  --color-primary-hover:#7CCDB4;
  --color-primary-light: rgba(91, 184, 154, 0.1);
  --color-accent:      #FBBF24;
  --color-accent-light: rgba(251, 191, 36, 0.1);
  --color-code-bg:     #0D0D14;
  --color-code-text:   #CDD6F4;
  --color-code-comment:#6C7086;
  --color-code-keyword:#CBA6F7;
  --color-code-string: #A6E3A1;
  --color-code-number: #FAB387;
  --color-code-func:   #89B4FA;
  --color-code-class:  #F9E2AF;
  --color-code-builtin:#F38BA8;
  --color-code-op:     #89DCEB;
  --color-success:     #5BB89A;
  --color-error:       #F38BA8;
  --color-output-bg:   #0A0A0A;
  --color-output-text: #CDD6F4;

  --shadow-sm: 0 1px 2px oklch(0 0 0 / 0.2);
  --shadow-md: 0 4px 12px oklch(0 0 0 / 0.3);
  --shadow-lg: 0 12px 32px oklch(0 0 0 / 0.4);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg:          #111111;
    --color-surface:     #1A1A1A;
    --color-surface-2:   #222222;
    --color-border:      #333333;
    --color-divider:     #2A2A2A;
    --color-text:        #E0DED8;
    --color-text-muted:  #8A8880;
    --color-text-faint:  #5A5850;
    --color-primary:     #5BB89A;
    --color-primary-hover:#7CCDB4;
    --color-primary-light: rgba(91, 184, 154, 0.1);
    --color-accent:      #FBBF24;
    --color-accent-light: rgba(251, 191, 36, 0.1);
    --color-code-bg:     #0D0D14;
    --color-code-text:   #CDD6F4;
    --color-success:     #5BB89A;
    --color-error:       #F38BA8;
    --color-output-bg:   #0A0A0A;
    --color-output-text: #CDD6F4;
    --shadow-sm: 0 1px 2px oklch(0 0 0 / 0.2);
    --shadow-md: 0 4px 12px oklch(0 0 0 / 0.3);
    --shadow-lg: 0 12px 32px oklch(0 0 0 / 0.4);
  }
}

/* ===== LAYOUT ===== */
.site-container {
  display: grid;
  grid-template-columns: 260px 1fr;
  min-height: 100dvh;
}

/* ===== SIDEBAR ===== */
.sidebar {
  position: sticky;
  top: 0;
  height: 100dvh;
  overflow-y: auto;
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  padding: var(--space-6) 0;
  display: flex;
  flex-direction: column;
  z-index: 40;
}

.sidebar-header {
  padding: 0 var(--space-5);
  margin-bottom: var(--space-6);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.logo-mark {
  width: 36px;
  height: 36px;
  flex-shrink: 0;
}

.logo-text {
  display: flex;
  flex-direction: column;
  gap: 0;
  line-height: 1.1;
}

.logo-text span:first-child {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.logo-text span:last-child {
  font-family: var(--font-body);
  font-weight: 400;
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 0 var(--space-3);
}

.nav-section-label {
  font-family: var(--font-body);
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-faint);
  padding: var(--space-4) var(--space-3) var(--space-2);
}

.nav-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  cursor: pointer;
  user-select: none;
  transition: all var(--transition-interactive);
  margin-bottom: 1px;
}

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

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

.nav-item .nav-icon {
  font-size: 0.875rem;
  width: 20px;
  text-align: center;
  flex-shrink: 0;
}

.nav-item .nav-label {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

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

.theme-toggle-btn {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  width: 100%;
  background: none;
  border: none;
  cursor: pointer;
  transition: all var(--transition-interactive);
}

.theme-toggle-btn:hover {
  background: var(--color-primary-light);
  color: var(--color-text);
}

/* ===== MOBILE HEADER ===== */
.mobile-header {
  display: none;
  position: sticky;
  top: 0;
  z-index: 50;
  background: oklch(from var(--color-bg) l c h / 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-3) var(--space-4);
  align-items: center;
  justify-content: space-between;
}

.mobile-header .logo-row {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.mobile-header .logo-row svg {
  width: 28px;
  height: 28px;
}

.mobile-header .logo-row span {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-sm);
}

.hamburger-btn {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  color: var(--color-text);
}

.hamburger-btn:hover {
  background: var(--color-primary-light);
}

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: oklch(0 0 0 / 0.5);
  z-index: 39;
}

/* ===== MAIN CONTENT ===== */
.main-content {
  padding: var(--space-8) var(--space-8);
  max-width: 920px;
  margin: 0 auto;
  width: 100%;
}

/* ===== HERO ===== */
.hero {
  padding: var(--space-12) 0 var(--space-8);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-3);
  background: var(--color-primary-light);
  color: var(--color-primary);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 500;
  margin-bottom: var(--space-4);
}

.hero h1 {
  font-family: var(--font-display);
  font-size: var(--text-2xl);
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.03em;
  margin-bottom: var(--space-4);
}

.hero h1 .accent {
  color: var(--color-primary);
}

.hero-desc {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  max-width: 60ch;
  line-height: 1.7;
}

.hero-stats {
  display: flex;
  gap: var(--space-8);
  margin-top: var(--space-6);
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-divider);
}

.hero-stat .stat-value {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--color-text);
}

.hero-stat .stat-label {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

/* ===== TUTORIAL SECTION ===== */
.tutorial-section {
  display: none;
  padding-bottom: var(--space-16);
}

.tutorial-section.active {
  display: block;
}

.section-header {
  margin-bottom: var(--space-8);
}

.section-number {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary);
  font-weight: 500;
  margin-bottom: var(--space-2);
}

.section-header h2 {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
  margin-bottom: var(--space-3);
}

.section-header .section-desc {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  max-width: 60ch;
}

/* ===== LESSON BLOCKS ===== */
.lesson-block {
  margin-bottom: var(--space-8);
}

.lesson-block h3 {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-3);
}

.lesson-block p {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  margin-bottom: var(--space-4);
  line-height: 1.7;
}

.lesson-block ul {
  margin-bottom: var(--space-4);
  padding-left: var(--space-5);
}

.lesson-block li {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
  line-height: 1.6;
}

.lesson-block li code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--color-code-bg);
  color: var(--color-code-func);
  padding: 0.15em 0.4em;
  border-radius: var(--radius-sm);
}

.lesson-block p code,
.section-header .section-desc code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--color-code-bg);
  color: var(--color-code-func);
  padding: 0.15em 0.4em;
  border-radius: var(--radius-sm);
}

.tip-box {
  background: var(--color-accent-light);
  border-left: 3px solid var(--color-accent);
  padding: var(--space-4);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin-bottom: var(--space-4);
}

.tip-box p {
  color: var(--color-text);
  font-size: var(--text-sm);
  margin: 0;
}

.tip-box strong {
  color: var(--color-accent);
}

/* ===== CODE EDITOR ===== */
.code-playground {
  background: var(--color-code-bg);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: var(--space-6);
  box-shadow: var(--shadow-lg);
}

.code-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-2) var(--space-4);
  background: oklch(from var(--color-code-bg) calc(l - 0.03) c h);
  border-bottom: 1px solid oklch(1 0 0 / 0.06);
}

.code-toolbar-left {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.dot-row {
  display: flex;
  gap: 6px;
}

.dot-row span {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.dot-row span:nth-child(1) { background: #FF5F56; }
.dot-row span:nth-child(2) { background: #FFBD2E; }
.dot-row span:nth-child(3) { background: #27C93F; }

.code-filename {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-code-comment);
}

.code-toolbar-right {
  display: flex;
  gap: var(--space-2);
}

.run-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-3);
  background: var(--color-primary);
  color: #FFFFFF;
  font-family: var(--font-body);
  font-size: var(--text-xs);
  font-weight: 600;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-interactive);
}

.run-btn:hover {
  background: var(--color-primary-hover);
  transform: translateY(-1px);
}

.run-btn:active {
  transform: translateY(0);
}

.run-btn.running {
  opacity: 0.7;
  pointer-events: none;
}

.run-btn svg {
  width: 14px;
  height: 14px;
}

.reset-btn {
  display: inline-flex;
  align-items: center;
  padding: var(--space-1) var(--space-2);
  color: var(--color-code-comment);
  font-size: var(--text-xs);
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-interactive);
}

.reset-btn:hover {
  color: var(--color-code-text);
  background: oklch(1 0 0 / 0.06);
}

.code-editor-wrapper {
  position: relative;
}

.code-editor {
  display: block;
  width: 100%;
  min-height: 180px;
  padding: var(--space-4);
  background: transparent;
  color: var(--color-code-text);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.7;
  border: none;
  outline: none;
  resize: vertical;
  tab-size: 4;
  white-space: pre;
  overflow-x: auto;
  caret-color: var(--color-primary);
}

.code-editor::placeholder {
  color: var(--color-code-comment);
}

.code-output-wrapper {
  border-top: 1px solid oklch(1 0 0 / 0.06);
}

.code-output-header {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  background: oklch(from var(--color-code-bg) calc(l - 0.02) c h);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-code-comment);
}

.code-output-header .output-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-code-comment);
  transition: background 0.3s;
}

.code-output-header .output-dot.success { background: #27C93F; }
.code-output-header .output-dot.error { background: #FF5F56; }

.code-output {
  padding: var(--space-3) var(--space-4);
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  line-height: 1.6;
  color: var(--color-code-string);
  min-height: 40px;
  max-height: 300px;
  overflow-y: auto;
  white-space: pre-wrap;
  word-break: break-word;
}

.code-output .error-text {
  color: var(--color-code-builtin);
}

.code-output .loading-text {
  color: var(--color-code-comment);
  animation: pulse 1.5s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

/* ===== PYODIDE STATUS ===== */
.pyodide-status {
  position: fixed;
  bottom: var(--space-4);
  right: var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  box-shadow: var(--shadow-md);
  z-index: 100;
  transition: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

.pyodide-status .status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-accent);
  transition: background 0.3s;
}

.pyodide-status.ready .status-dot {
  background: var(--color-success);
}

.pyodide-status.ready {
  opacity: 0;
  transform: translateY(10px);
  pointer-events: none;
}

/* ===== SECTION NAVIGATION ===== */
.section-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--space-8);
  border-top: 1px solid var(--color-divider);
  margin-top: var(--space-8);
}

.section-nav-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text);
  cursor: pointer;
  transition: all var(--transition-interactive);
}

.section-nav-btn:hover {
  background: var(--color-primary-light);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.section-nav-btn.hidden {
  visibility: hidden;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  .site-container {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: fixed;
    left: -280px;
    top: 0;
    width: 280px;
    transition: left 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    z-index: 50;
  }

  .sidebar.open {
    left: 0;
  }

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

  .mobile-header {
    display: flex;
  }

  .main-content {
    padding: var(--space-4) var(--space-4);
  }

  .hero {
    padding: var(--space-6) 0 var(--space-4);
  }

  .hero-stats {
    flex-wrap: wrap;
    gap: var(--space-4);
  }

  .section-nav {
    flex-direction: column;
    gap: var(--space-3);
  }

  .section-nav-btn {
    width: 100%;
    justify-content: center;
  }

  .section-nav-btn.hidden {
    display: none;
  }
}

/* ===== SCROLL REVEALS ===== */
.reveal {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s cubic-bezier(0.16, 1, 0.3, 1),
              transform 0.5s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== PYODIDE LOADING SCREEN ===== */
.pyodide-loader {
  position: fixed;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--color-bg);
  z-index: 1000;
  transition: opacity 0.5s, visibility 0.5s;
}

.pyodide-loader.hidden {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.pyodide-loader .loader-spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin-bottom: var(--space-4);
}

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

.pyodide-loader p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

.pyodide-loader .loader-sub {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  margin-top: var(--space-2);
}