@import url('https://fonts.googleapis.com/css2?family=Google+Sans:wght@400;500;700&family=Roboto:wght@400;500;700&family=Roboto+Mono:wght@400;500&display=swap');

:root {
  --g-blue: #1a73e8;
  --g-blue-hover: #1557b0;
  --g-blue-soft: #e8f0fe;
  --g-green: #188038;
  --g-green-soft: #e6f4ea;
  --g-amber: #b06000;
  --g-amber-soft: #fef7e0;
  --g-bg: #f8f9fa;
  --g-surface: #ffffff;
  --g-text: #202124;
  --g-text-secondary: #5f6368;
  --g-text-muted: #80868b;
  --g-border: #dadce0;
  --g-border-subtle: #e8eaed;
  --g-code-bg: #1e293b;
  --g-code-header: #0f172a;
  --g-code-text: #f1f5f9;
  --header-height: 64px;
  --sidebar-width: 310px;
}

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

html,
body {
  height: 100%;
  font-family: 'Roboto', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  color: var(--g-text);
  background-color: var(--g-bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* Top Google Codelabs App Bar */
.codelab-topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: var(--g-surface);
  border-bottom: 1px solid var(--g-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  z-index: 100;
  box-shadow: 0 1px 3px rgba(60, 64, 67, 0.08);
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 14px;
  min-width: 0;
}

.menu-toggle-btn {
  display: none;
  background: transparent;
  border: 1px solid var(--g-border);
  border-radius: 6px;
  width: 36px;
  height: 36px;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--g-text-secondary);
  font-size: 18px;
}

.back-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  color: var(--g-text-secondary);
  text-decoration: none;
  transition: background-color 0.15s ease, color 0.15s ease;
  flex-shrink: 0;
}

.back-link:hover {
  background-color: var(--g-bg);
  color: var(--g-blue);
}

.codelab-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--g-blue-soft);
  color: var(--g-blue);
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 12px;
  font-weight: 700;
  padding: 4px 10px;
  border-radius: 6px;
  letter-spacing: 0.02em;
  flex-shrink: 0;
}

.codelab-title {
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 17px;
  font-weight: 500;
  color: var(--g-text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.topbar-right {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
}

.vars-toggle-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--g-surface);
  border: 1px solid var(--g-border);
  color: var(--g-text-secondary);
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 13px;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.vars-toggle-btn:hover,
.vars-toggle-btn.active {
  border-color: var(--g-blue);
  color: var(--g-blue);
  background: var(--g-blue-soft);
}

.gdoc-link-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--g-surface);
  border: 1px solid var(--g-border);
  color: var(--g-text-secondary);
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 13px;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: 6px;
  text-decoration: none;
  transition: all 0.15s ease;
}

.gdoc-link-btn:hover {
  border-color: var(--g-blue);
  color: var(--g-blue);
  background: var(--g-bg);
}

.time-remaining {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 13px;
  font-weight: 500;
  color: var(--g-text-secondary);
  background: var(--g-bg);
  padding: 6px 12px;
  border-radius: 20px;
  border: 1px solid var(--g-border-subtle);
}

/* Progress Line under Header */
.progress-bar-track {
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  height: 3px;
  background: var(--g-border-subtle);
  z-index: 101;
}

.progress-bar-fill {
  height: 100%;
  background: var(--g-blue);
  width: 10%;
  transition: width 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Collapsible Lab Variables Bar */
.lab-vars-panel {
  position: fixed;
  top: calc(var(--header-height) + 3px);
  left: var(--sidebar-width);
  right: 0;
  background: #ffffff;
  border-bottom: 1px solid var(--g-border);
  padding: 12px 28px;
  z-index: 95;
  box-shadow: 0 4px 12px rgba(60, 64, 67, 0.08);
  display: none;
}

.lab-vars-panel.open {
  display: block;
}

.lab-vars-inner {
  max-width: 860px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: 14px;
}

.var-field {
  display: flex;
  flex-direction: column;
  gap: 4px;
  flex: 1 1 160px;
}

.var-field label {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--g-text-secondary);
}

.var-field input {
  font-family: 'Roboto Mono', monospace;
  font-size: 12.5px;
  padding: 6px 10px;
  border: 1px solid var(--g-border);
  border-radius: 5px;
  color: var(--g-text);
  background: var(--g-bg);
}

.var-field input:focus {
  outline: none;
  border-color: var(--g-blue);
  background: #ffffff;
}

.var-reset-btn {
  font-size: 12px;
  font-weight: 500;
  color: var(--g-blue);
  background: transparent;
  border: 1px solid var(--g-border);
  padding: 7px 12px;
  border-radius: 5px;
  cursor: pointer;
}

.var-reset-btn:hover {
  background: var(--g-blue-soft);
  border-color: var(--g-blue);
}

/* Main Layout */
.codelab-layout {
  display: flex;
  padding-top: calc(var(--header-height) + 3px);
  min-height: 100vh;
}

/* Left Stepper Drawer */
.codelab-drawer {
  position: fixed;
  top: calc(var(--header-height) + 3px);
  left: 0;
  bottom: 0;
  width: var(--sidebar-width);
  background: var(--g-surface);
  border-right: 1px solid var(--g-border);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  overflow-y: auto;
  z-index: 90;
  padding: 16px 12px;
}

.steps-nav {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.step-nav-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 10px 12px;
  border-radius: 8px;
  cursor: pointer;
  color: var(--g-text-secondary);
  transition: background-color 0.15s ease, color 0.15s ease;
  user-select: none;
  border: none;
  background: transparent;
  width: 100%;
  text-align: left;
  font-family: inherit;
}

.step-nav-item:hover {
  background-color: var(--g-bg);
  color: var(--g-text);
}

.step-nav-item.active {
  background-color: var(--g-blue-soft);
  color: var(--g-blue);
  font-weight: 500;
}

.step-circle {
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: #e8eaed;
  color: var(--g-text-secondary);
  font-size: 12px;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-top: 1px;
  transition: all 0.15s ease;
}

.step-nav-item.active .step-circle {
  background: var(--g-blue);
  color: #ffffff;
}

.step-nav-item.completed:not(.active) .step-circle {
  background: var(--g-green-soft);
  color: var(--g-green);
}

.step-nav-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 0;
}

.step-nav-label {
  font-size: 13.5px;
  line-height: 1.35;
}

.step-nav-duration {
  font-size: 11px;
  color: var(--g-text-muted);
}

.step-nav-item.active .step-nav-duration {
  color: var(--g-blue);
  opacity: 0.85;
}

.drawer-footer {
  margin-top: 20px;
  padding: 12px;
  border-top: 1px solid var(--g-border-subtle);
  font-size: 12px;
  color: var(--g-text-muted);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.drawer-footer a {
  color: var(--g-blue);
  text-decoration: none;
  font-weight: 500;
}

.drawer-footer a:hover {
  text-decoration: underline;
}

/* Main Content Stage */
.codelab-main {
  flex: 1;
  margin-left: var(--sidebar-width);
  padding: 32px 28px 110px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.codelab-step-card {
  width: 100%;
  max-width: 860px;
  background: var(--g-surface);
  border: 1px solid var(--g-border);
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(60, 64, 67, 0.12), 0 4px 8px rgba(60, 64, 67, 0.04);
  padding: 40px 48px;
  display: none;
  animation: fadeInStep 0.2s ease-out;
}

.codelab-step-card.active {
  display: block;
}

@keyframes fadeInStep {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Step Header Inside Card */
.step-header {
  border-bottom: 1px solid var(--g-border-subtle);
  padding-bottom: 20px;
  margin-bottom: 24px;
}

.step-eyebrow {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
}

.step-counter {
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 12.5px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--g-blue);
}

.step-duration-badge {
  font-size: 12px;
  font-weight: 500;
  color: var(--g-text-secondary);
  background: var(--g-bg);
  padding: 3px 10px;
  border-radius: 12px;
  border: 1px solid var(--g-border-subtle);
}

.step-heading {
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 26px;
  font-weight: 400;
  color: var(--g-text);
  line-height: 1.3;
}

/* Step Body Typography */
.step-body p {
  font-size: 15px;
  color: #3c4043;
  margin-bottom: 16px;
  line-height: 1.68;
}

.step-body h3 {
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 18px;
  font-weight: 500;
  color: var(--g-text);
  margin: 28px 0 12px;
  padding-top: 8px;
  border-top: 1px solid var(--g-border-subtle);
}

.step-body h3:first-of-type {
  border-top: none;
  padding-top: 0;
}

.step-body ul,
.step-body ol {
  margin: 0 0 18px 24px;
  color: #3c4043;
  font-size: 15px;
}

.step-body li {
  margin-bottom: 10px;
  line-height: 1.62;
}

.step-body code:not(pre code) {
  font-family: 'Roboto Mono', monospace;
  font-size: 13px;
  background: #f1f3f4;
  color: #188038;
  padding: 2px 6px;
  border-radius: 4px;
  word-break: break-word;
}

/* Architecture Diagram Showcase */
.diagram-container {
  margin: 24px 0;
  padding: 20px;
  background: #ffffff;
  border: 1px solid var(--g-border);
  border-radius: 8px;
  text-align: center;
}

.diagram-container img {
  max-width: 100%;
  height: auto;
  border-radius: 4px;
}

.diagram-caption {
  margin-top: 10px;
  font-size: 12.5px;
  color: var(--g-text-secondary);
  font-style: italic;
}

/* Google Codelabs Info & Tip Callouts */
.callout-box {
  margin: 20px 0;
  padding: 16px 20px;
  border-radius: 6px;
  border-left: 4px solid var(--g-blue);
  background: var(--g-blue-soft);
  font-size: 14.5px;
  color: var(--g-text);
  line-height: 1.6;
}

.callout-box.tip {
  border-left-color: var(--g-green);
  background: var(--g-green-soft);
}

.callout-box.warning {
  border-left-color: var(--g-amber);
  background: var(--g-amber-soft);
}

.callout-box strong {
  font-weight: 700;
}

/* Data Table */
.table-wrapper {
  margin: 20px 0 24px;
  overflow-x: auto;
  border: 1px solid var(--g-border);
  border-radius: 8px;
}

.codelab-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13.5px;
}

.codelab-table th {
  background: #f1f3f4;
  color: var(--g-text);
  font-weight: 700;
  text-align: left;
  padding: 12px 14px;
  border-bottom: 1px solid var(--g-border);
}

.codelab-table td {
  padding: 12px 14px;
  border-bottom: 1px solid var(--g-border-subtle);
  color: #3c4043;
  vertical-align: top;
}

.codelab-table tr:last-child td {
  border-bottom: none;
}

/* Code Block with Header & Copy Button */
.code-snippet {
  margin: 14px 0 26px;
  border-radius: 8px;
  overflow: hidden;
  background: var(--g-code-bg);
  border: 1px solid #334155;
  box-shadow: 0 2px 6px rgba(15, 23, 42, 0.12);
}

.code-snippet-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 14px;
  background: var(--g-code-header);
  border-bottom: 1px solid #334155;
}

.code-lang-tag {
  font-family: 'Roboto Mono', monospace;
  font-size: 11.5px;
  font-weight: 500;
  color: #94a3b8;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.copy-code-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.16);
  color: #e2e8f0;
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 12px;
  font-weight: 500;
  padding: 4px 10px;
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.copy-code-btn:hover {
  background: rgba(255, 255, 255, 0.16);
  color: #ffffff;
}

.copy-code-btn.copied {
  background: #166534;
  border-color: #22c55e;
  color: #ffffff;
}

.code-snippet pre {
  padding: 16px 18px;
  overflow-x: auto;
  font-family: 'Roboto Mono', monospace;
  font-size: 13px;
  line-height: 1.58;
  color: var(--g-code-text);
  margin: 0;
}

.code-snippet code {
  font-family: 'Roboto Mono', monospace;
  background: transparent;
  color: inherit;
  padding: 0;
}

/* Bottom Navigation Bar */
.codelab-bottom-nav {
  width: 100%;
  max-width: 860px;
  margin-top: 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: 'Google Sans', 'Roboto', sans-serif;
  font-size: 14px;
  font-weight: 500;
  padding: 10px 22px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
  border: 1px solid transparent;
  box-shadow: 0 1px 2px rgba(60, 64, 67, 0.15);
}

.nav-btn-prev {
  background: var(--g-surface);
  color: var(--g-blue);
  border-color: var(--g-border);
}

.nav-btn-prev:hover:not(:disabled) {
  background: var(--g-bg);
  border-color: var(--g-blue);
}

.nav-btn-next {
  background: var(--g-blue);
  color: #ffffff;
}

.nav-btn-next:hover:not(:disabled) {
  background: var(--g-blue-hover);
}

.nav-btn.complete-btn {
  background: var(--g-green);
  color: #ffffff;
}

.nav-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  box-shadow: none;
}

.step-dots-indicator {
  font-size: 13px;
  color: var(--g-text-secondary);
}

@media (max-width: 960px) {
  .menu-toggle-btn {
    display: inline-flex;
  }

  .codelab-drawer {
    transform: translateX(-100%);
    transition: transform 0.22s ease;
    box-shadow: 4px 0 16px rgba(0, 0, 0, 0.12);
  }

  .codelab-drawer.open {
    transform: translateX(0);
  }

  .codelab-main {
    margin-left: 0;
    padding: 20px 14px 90px;
  }

  .lab-vars-panel {
    left: 0;
    padding: 12px 16px;
  }

  .codelab-step-card {
    padding: 24px 20px;
  }
}