/**
 * Shared base styles for DroneBlocks trifecta articles.
 * All articles link to this file instead of duplicating inline styles.
 * Article-specific styles can be added in a <style> block after this link.
 */

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

:root {
  --db-navy: #003A5D;
  --db-cyan: #00A7E1;
  --db-green: #1B9E5A;
  --db-orange: #E07842;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;

  /* Spacing scale — use these, not one-off values (8 / 12 / 16 / 20 / 24 / 32 / 48).
     --space-block is the standard vertical gap between article content blocks. */
  --space-1: 8px;
  --space-2: 12px;
  --space-3: 16px;
  --space-4: 20px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-block: 24px;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--gray-50);
  color: var(--gray-800);
  line-height: 1.7;
}

/* ─── Header ────────────────────────────────────────────────── */

.site-header {
  background: white;
  border-bottom: 1px solid var(--gray-200);
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 100;
}

/* Header layout: the logo is the left brand anchor and the "← Back to <section>" link
   sits on the right. The wrapper div holds [back-link, logo] in DOM order; row-reverse
   + space-between renders them logo-left / back-right across every article. */
.site-header > div { width: 100%; justify-content: space-between; flex-direction: row-reverse; }

.site-header a {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
}

.site-header img {
  height: 32px;
  width: auto;
}

.header-cta {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--db-cyan);
  color: white;
  font-family: inherit;
  font-weight: 600;
  font-size: 0.85rem;
  padding: 8px 18px;
  border-radius: 8px;
  text-decoration: none;
  transition: background 0.15s;
}

.header-cta:hover { background: #0095cc; }

/* ─── Article container ─────────────────────────────────────── */

.article-container {
  max-width: 760px;
  margin: 0 auto;
  padding: 48px 24px 96px;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 20px;
  font-size: 0.85rem;
  color: var(--gray-500);
}

.article-tag {
  display: inline-block;
  background: rgba(0, 167, 225, 0.1);
  color: var(--db-cyan);
  padding: 4px 10px;
  border-radius: 12px;
  font-weight: 600;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  text-decoration: none;
}
a.article-tag {
  cursor: pointer;
  transition: background 0.15s;
}
a.article-tag:hover {
  background: rgba(0, 167, 225, 0.2);
}

.article-tag.green {
  background: rgba(27, 158, 90, 0.1);
  color: var(--db-green);
}

/* Route/address badge alongside a heading, e.g. "DEXI GCS  /gcs" */
.route-badge {
  display: inline-block;
  margin-left: 8px;
  vertical-align: middle;
  background: var(--gray-100);
  color: var(--gray-500);
  border-radius: 6px;
  padding: 3px 8px;
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
  /* Fixed, not em: badges stay the same size on an h2 and an h3. */
  font-size: 0.78rem;
  font-weight: 500;
  letter-spacing: 0;
  white-space: nowrap;
}

/* ─── Typography ────────────────────────────────────────────── */

h1 {
  font-size: 2rem;
  font-weight: 700;
  color: var(--db-navy);
  line-height: 1.3;
  margin-bottom: 16px;
}

.article-subtitle {
  font-size: 1.1rem;
  color: var(--gray-500);
  margin-bottom: 32px;
  line-height: 1.6;
}

h2 {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--db-navy);
  margin-top: 48px;
  margin-bottom: 16px;
  padding-top: 16px;
}

h3 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--db-navy);
  margin-top: 32px;
  margin-bottom: 12px;
}

/* Inline body links (not class-based nav/card links) */
.article-container p a:not([class]) {
  color: var(--db-cyan);
  font-weight: 600;
  text-decoration: none;
  border-bottom: 1px solid rgba(0, 167, 225, 0.35);
  transition: color 0.15s, border-color 0.15s;
}
.article-container p a:not([class]):hover {
  color: var(--db-navy);
  border-bottom-color: var(--db-navy);
}

p {
  margin-bottom: 16px;
  font-size: 1rem;
  color: var(--gray-700);
}

/* ---- Article body lists — branded markers + proper rhythm.
   Applies in BOTH content wrappers: .article-container (standalone article files)
   AND .lesson-content (the portal lesson page injects the inner HTML there, so any
   .article-container-only rule never reaches it). Scoped with :not([class]) so the
   specialized lists (.toc / .objectives-list / .kv-list) keep their own styling. ---- */
.article-container ul:not([class]),
.lesson-content ul:not([class]),
.overview-body ul:not([class]),
.article-container ol:not([class]),
.lesson-content ol:not([class]),
.overview-body ol:not([class]) {
  margin: 4px 0 22px;
  padding-left: 1.55rem;
  font-size: 1rem;
  color: var(--gray-700);
}
.article-container ul:not([class]),
.lesson-content ul:not([class]),
.overview-body ul:not([class]) { list-style: none; }
.article-container ul:not([class]) > li,
.lesson-content ul:not([class]) > li,
.overview-body ul:not([class]) > li,
.article-container ol:not([class]) > li,
.lesson-content ol:not([class]) > li,
.overview-body ol:not([class]) > li {
  position: relative;
  margin-bottom: 0.6rem;
  line-height: 1.7;
  padding-left: 0.2rem;
}
.article-container ul:not([class]) > li::before,
.lesson-content ul:not([class]) > li::before,
.overview-body ul:not([class]) > li::before {
  content: "";
  position: absolute;
  left: -1.05rem;
  top: 0.62em;
  width: 6px;
  height: 6px;
  border-radius: 2px;            /* soft square in brand cyan — cleaner than the default dot */
  background: var(--db-cyan);
}
.article-container ol:not([class]) > li::marker,
.lesson-content ol:not([class]) > li::marker,
.overview-body ol:not([class]) > li::marker {
  color: var(--db-cyan);
  font-weight: 700;
}
.article-container ul:not([class]) ul,
.lesson-content ul:not([class]) ul,
.article-container ul:not([class]) ol,
.lesson-content ul:not([class]) ol,
.article-container ol:not([class]) ul,
.lesson-content ol:not([class]) ul,
.article-container ol:not([class]) ol,
.lesson-content ol:not([class]) ol {
  margin: 0.55rem 0 0.3rem;
}

code {
  background: var(--gray-100);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.9em;
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
}

hr {
  border: none;
  border-top: 1px solid var(--gray-200);
  margin: 48px 0;
}

/* ─── Video player & sticky mini-player ─────────────────────── */

.video-wrapper {
  position: relative;
  border-radius: 12px;
  overflow: hidden;
  margin-bottom: 40px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
  background: #000;
}

.video-wrapper video,
.video-wrapper iframe {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
  border: none;
}

/* Embedded interactive figure (Ground School 3D). Taller than a video: the
   figure carries a readout card and a control bar as well as the scene. */
.figure-embed {
  position: relative;
  border-radius: 12px;
  overflow: hidden;
  margin: 24px 0 12px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
  background: #0b1520;
}
.figure-embed iframe {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 4 / 3;
  min-height: 420px;
  border: none;
}
.figure-embed + .caption { margin-top: 0; }
@media (max-width: 640px) {
  .figure-embed iframe { aspect-ratio: 3 / 4; min-height: 380px; }
}

.video-wrapper.sticky {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 360px;
  margin-bottom: 0;
  z-index: 1000;
  border-radius: 10px;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.25);
  overflow: visible;
  animation: slideIn 0.25s ease;
}

.video-wrapper.sticky video,
.video-wrapper.sticky iframe { border-radius: 10px; }

.video-placeholder { height: 1px; margin: 0; }

.video-placeholder.active {
  height: auto;
  aspect-ratio: 16 / 9;
  border-radius: 12px;
  margin-bottom: 40px;
  background: var(--gray-100);
  border: 2px dashed var(--gray-200);
}

.sticky-close {
  display: none;
  position: absolute;
  top: -12px;
  right: -12px;
  width: 28px;
  height: 28px;
  background: var(--gray-800);
  color: white;
  border: 2px solid white;
  border-radius: 50%;
  font-size: 14px;
  line-height: 1;
  cursor: pointer;
  z-index: 1001;
  align-items: center;
  justify-content: center;
}

.video-wrapper.sticky .sticky-close { display: flex; }

@keyframes slideIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ─── Timestamps ────────────────────────────────────────────── */

.timestamp {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  background: var(--gray-100);
  color: var(--db-cyan);
  padding: 3px 10px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  text-decoration: none;
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
  transition: all 0.15s ease;
  vertical-align: middle;
  margin-left: 2px;
  cursor: pointer;
}

.timestamp:hover {
  background: rgba(0, 167, 225, 0.12);
  color: #0090c0;
}

.timestamp svg {
  width: 12px;
  height: 12px;
  flex-shrink: 0;
}

/* ─── Video thumbnails (inline chips) ───────────────────────── */

.video-thumb {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: white;
  border: 1px solid var(--gray-200);
  border-radius: 8px;
  padding: 4px 10px 4px 4px;
  text-decoration: none;
  cursor: pointer;
  transition: all 0.15s ease;
  vertical-align: middle;
  margin: 4px 0;
}

.video-thumb:hover {
  border-color: var(--db-cyan);
  box-shadow: 0 2px 8px rgba(0, 167, 225, 0.1);
}

.video-thumb img {
  width: 48px;
  height: 28px;
  object-fit: cover;
  border-radius: 4px;
}

.video-thumb span {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--db-cyan);
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
}

/* ─── Table of contents ─────────────────────────────────────── */

.toc {
  background: white;
  border-radius: 12px;
  padding: 24px 28px;
  margin-bottom: 0;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.toc h3 {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--gray-500);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 12px;
}

.toc ol {
  list-style: none;
  counter-reset: toc;
  padding: 0;
}

.toc li {
  counter-increment: toc;
  margin-bottom: 6px;
}

.toc li a {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--gray-700);
  font-size: 0.9rem;
  font-weight: 500;
  padding: 6px 0;
  transition: color 0.15s ease;
  cursor: pointer;
}

.toc li a:hover { color: var(--db-cyan); }

.toc li a::before {
  content: counter(toc);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: 6px;
  background: var(--gray-100);
  color: var(--gray-500);
  font-size: 0.75rem;
  font-weight: 600;
  flex-shrink: 0;
}

.toc li a .toc-time {
  margin-left: auto;
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
  font-size: 0.75rem;
  color: var(--gray-400);
}

/* ─── Feature cards ─────────────────────────────────────────── */

.feature-card {
  background: white;
  border-radius: 12px;
  padding: 18px 20px;
  margin: var(--space-block) 0;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  border: 1px solid var(--gray-200);
  border-left: 4px solid var(--db-cyan);
}

.feature-card.math { border-left-color: var(--db-orange); }
.feature-card.loops { border-left-color: var(--db-orange); }
.feature-card.sim { border-left-color: var(--db-green); }
.feature-card.tools { border-left-color: var(--db-green); }

.feature-card h3 {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--db-navy);
  /* reset the leaked top margin from the base h3 rule — the title should sit
     at the top of the card, not float 32px down from it. */
  margin-top: 0;
  margin-bottom: 10px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--gray-100);
}

.feature-card p {
  margin-bottom: 0;
  font-size: 0.9rem;
  color: var(--gray-600);
}

/* Responsive card row — short spec lists (Hardware / Tools) sit side by side on
   desktop and stack on mobile. auto-fit means a lone card fills the full width. */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--space-3);
  margin: var(--space-block) 0;
  align-items: stretch;
}
.feature-grid .feature-card {
  margin: 0;          /* the grid gap owns the spacing */
  height: 100%;       /* equal-height cards when side by side */
}

/* ─── Equation callout box ─────────────────────────────────── */

.equation-box {
  background: linear-gradient(135deg, rgba(0, 58, 93, 0.04), rgba(0, 167, 225, 0.06));
  border: 1px solid rgba(0, 167, 225, 0.15);
  border-radius: 12px;
  padding: 24px;
  margin: 20px 0;
  text-align: center;
}

.equation {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--db-navy);
  letter-spacing: 0.02em;
  margin-bottom: 6px;
}

.equation-label {
  font-size: 0.82rem;
  color: var(--gray-500);
}

/* ─── Code comparison panels ────────────────────────────────── */

.code-comparison {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}

.code-comparison .code-panel {
  background: white;
  border-radius: 12px;
  padding: 20px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.code-panel h4 {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 10px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--gray-100);
}

.code-panel h4.before { color: var(--gray-400); }
.code-panel h4.after { color: var(--db-green); }

.code-panel .block-list {
  font-size: 0.85rem;
  color: var(--gray-600);
  line-height: 1.8;
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
}

.code-panel .block-list .highlight {
  color: var(--db-orange);
  font-weight: 600;
}

.code-panel .block-list .indent { padding-left: 20px; }
.code-panel .block-list .indent-2 { padding-left: 40px; }

/* ─── Math tables ───────────────────────────────────────────── */

.math-table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 0.9rem;
}

.math-table th,
.math-table td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid var(--gray-200);
}

.math-table th {
  background: var(--gray-100);
  font-weight: 600;
  color: var(--db-navy);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.math-table td { color: var(--gray-700); }

/* ─── Blocks preview ────────────────────────────────────────── */

.blocks-preview {
  background: white;
  border-radius: 12px;
  padding: 20px 24px;
  margin: 16px 0;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
  font-size: 0.85rem;
  line-height: 1.8;
  color: var(--gray-600);
}

.blocks-preview .highlight {
  color: var(--db-orange);
  font-weight: 600;
}

.blocks-preview .indent { padding-left: 20px; }
.blocks-preview .indent-2 { padding-left: 40px; }

/* ─── Mission picker ────────────────────────────────────────── */

.mission-picker {
  position: relative;
  background: white;
  border-radius: 16px;
  padding: 32px;
  margin: 48px 0 24px;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
  border: 1px solid var(--gray-200);
}

/* Locked overlay — covers the mission picker for non-authenticated users */
.picker-locked-overlay {
  position: absolute;
  inset: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(4px);
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.picker-locked-card {
  text-align: center;
  max-width: 320px;
  padding: 20px;
}

.picker-locked-card .lock-icon {
  color: var(--db-navy);
  margin-bottom: 12px;
}

.picker-locked-card h4 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--db-navy);
  margin-bottom: 6px;
}

.picker-locked-card > p {
  font-size: 0.9rem;
  color: var(--gray-500);
  margin-bottom: 16px;
}

.picker-locked-cta {
  display: inline-block;
  background: var(--db-cyan);
  color: white;
  font-weight: 700;
  font-size: 0.9rem;
  padding: 10px 28px;
  border-radius: 8px;
  text-decoration: none;
  transition: background 0.15s;
}

.picker-locked-cta:hover {
  background: #0090c0;
}

.picker-locked-login {
  display: block;
  margin-top: 10px;
  font-size: 0.82rem;
  color: var(--gray-400);
}

.picker-locked-login a {
  color: var(--db-cyan);
  text-decoration: none;
  font-weight: 600;
}

.picker-locked-login a:hover {
  text-decoration: underline;
}

.mission-picker h3 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--db-navy);
  margin-bottom: 4px;
}

.mission-picker > p {
  font-size: 0.85rem;
  color: var(--gray-500);
  margin-bottom: 20px;
}

.picker-label {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--gray-400);
  margin-bottom: 8px;
}

.picker-scenes {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
}

.picker-scene {
  flex: 1;
  border-radius: 10px;
  overflow: hidden;
  border: 2px solid var(--gray-200);
  background: white;
  cursor: pointer;
  transition: all 0.2s ease;
}

.picker-scene:hover { border-color: var(--gray-300); }

.picker-scene.selected {
  border-color: var(--db-cyan);
  box-shadow: 0 0 0 3px rgba(0, 167, 225, 0.12);
}

.picker-scene-img {
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
}

.picker-scene-img.city { background: linear-gradient(135deg, #1e3a5f, #2d5f8a); }
.picker-scene-img.mars { background: linear-gradient(135deg, #5a1a0a, #a0522d); }
.picker-scene-img.tundra { background: linear-gradient(135deg, #1a3a4a, #5f8fa0); }

.picker-scene-body { padding: 8px 10px; text-align: center; }

.picker-scene-body h4 {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--gray-800);
  margin-bottom: 1px;
}

.picker-scene-body p {
  font-size: 0.6rem;
  color: var(--gray-500);
  margin-bottom: 0;
}

/* Shape picker grid */
.picker-shapes {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-bottom: 20px;
}

.picker-shape {
  border: 2px solid var(--gray-200);
  border-radius: 10px;
  padding: 14px 10px;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s ease;
  background: white;
}

.picker-shape:hover {
  border-color: var(--gray-300);
  background: var(--gray-50);
}

.picker-shape.selected {
  border-color: var(--db-cyan);
  box-shadow: 0 0 0 3px rgba(0, 167, 225, 0.12);
  background: rgba(0, 167, 225, 0.03);
}

.picker-shape .shape-icon {
  font-size: 1.4rem;
  margin-bottom: 6px;
}

.picker-shape h5 {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--gray-800);
  margin-bottom: 2px;
}

.picker-shape p {
  font-size: 0.65rem;
  color: var(--gray-500);
  margin-bottom: 0;
}

.picker-launch {
  background: linear-gradient(135deg, var(--db-navy), #005580);
  border-radius: 12px;
  padding: 16px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: white;
}

.picker-launch-info h4 {
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 2px;
  color: white;
}

.picker-launch-info p {
  font-size: 0.7rem;
  color: rgba(255,255,255,0.65);
  margin-bottom: 0;
}

.picker-launch-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  background: var(--db-cyan);
  color: white;
  border: none;
  border-radius: 8px;
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.15s ease;
  flex-shrink: 0;
}

.picker-launch-btn:hover {
  background: #0095cc;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0, 167, 225, 0.3);
}

/* ─── Lesson navigation ─────────────────────────────────────── */

.lesson-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 32px 0;
}

.lesson-nav a {
  display: block;
  background: white;
  border-radius: 12px;
  padding: 16px 20px;
  text-decoration: none;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  border: 1px solid var(--gray-200);
  transition: all 0.15s ease;
}

.lesson-nav a:hover {
  border-color: var(--db-cyan);
  box-shadow: 0 2px 8px rgba(0, 167, 225, 0.1);
}

.lesson-nav .nav-label {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--gray-400);
  margin-bottom: 4px;
}

.lesson-nav .nav-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--db-navy);
}

/* ─── Course navigation (prev/next between lessons) ─────────── */
/* Rendered at the foot of a standalone article so the static /articles/
   URLs chain together. The in-app course player strips this block and
   renders its own footer nav, so it never doubles up.
   Anchors may be plain text (legacy articles) or carry
   .nav-label / .nav-title spans. Both are handled. */

.course-nav {
  display: flex;
  gap: 16px;
  margin: 40px 0 8px;
  padding-top: 28px;
  border-top: 1px solid var(--gray-200);
}

.course-nav a {
  flex: 0 1 calc(50% - 8px);
  display: block;
  background: white;
  border-radius: 12px;
  padding: 14px 18px;
  text-decoration: none;
  color: var(--db-navy);
  font-size: 0.9rem;
  font-weight: 600;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  border: 1px solid var(--gray-200);
  transition: all 0.15s ease;
}

.course-nav a:hover {
  border-color: var(--db-cyan);
  box-shadow: 0 2px 8px rgba(0, 167, 225, 0.1);
}

/* A lone "next" (first lesson) sits right; a lone "prev" (last) stays left. */
.course-nav .nav-next {
  margin-left: auto;
  text-align: right;
}

.course-nav .nav-label {
  display: block;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--gray-400);
  margin-bottom: 4px;
}

.course-nav .nav-title {
  display: block;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--db-navy);
}

@media (max-width: 640px) {
  .course-nav { flex-direction: column; }
  .course-nav a { flex: 1 1 auto; }
  .course-nav .nav-next { margin-left: 0; text-align: left; }
}

/* ─── Objectives list ───────────────────────────────────────── */

.objectives-list {
  list-style: none;
  padding: 0;
  margin: 16px 0;
}

.objectives-list li {
  padding: 8px 0 8px 28px;
  position: relative;
  font-size: 0.95rem;
  color: var(--gray-700);
}

.objectives-list li::before {
  content: '\2713';
  position: absolute;
  left: 0;
  color: var(--db-green);
  font-weight: 700;
}

/* ─── Physical block lessons (Mars Mission Builder etc.) ───── */

.block-sheet-container {
  margin: 1.5rem 0;
  background: var(--gray-50);
  border-radius: 12px;
  padding: 1.5rem;
  text-align: center;
}
.block-sheet-container svg { max-width: 100%; height: auto; }
.block-sheet-label {
  color: var(--gray-500);
  font-size: 0.85rem;
  margin-bottom: 1rem;
}

.challenge-card {
  background: linear-gradient(135deg, var(--db-navy) 0%, #00527a 100%);
  color: white;
  border-radius: 12px;
  padding: 2rem;
  margin: 1.5rem 0;
}
.challenge-card h3 {
  color: var(--db-cyan);
  margin-top: 0;
  font-size: 1.1rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.challenge-card p { line-height: 1.7; margin-bottom: 0; color: white; }

.success-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: #1B9E5A22;
  color: var(--db-green);
  padding: 6px 14px;
  border-radius: 20px;
  font-weight: 600;
  font-size: 0.9rem;
  margin-top: 1rem;
}

.hint-box {
  background: #FFF7ED;
  border-left: 4px solid var(--db-orange);
  border-radius: 0 8px 8px 0;
  padding: 1rem 1.5rem;
  margin: 1.5rem 0;
}
.hint-box h4 { color: var(--db-orange); margin-top: 0; margin-bottom: 0.5rem; }
.hint-box ul { margin: 0; padding-left: 1.2rem; }
.hint-box li { margin-bottom: 0.4rem; line-height: 1.6; }

.section-toggles {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 1rem 0;
}
.toggle-solution {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--db-navy);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
  font-size: 0.95rem;
}
.toggle-solution:hover { background: #00527a; }
.solution-hidden { display: none; }

/* ─── Mission launcher callout ─────────────────────────────── */

.mission-launcher {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  background: white;
  border: 1px solid var(--gray-200);
  border-radius: 12px;
  padding: 1.25rem 1.5rem;
  margin: 1.5rem 0;
  box-shadow: 0 1px 2px rgba(0,0,0,0.04);
}
.mission-launcher-info { flex: 1; min-width: 0; }
.mission-launcher-info h3 {
  color: var(--db-navy);
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 0.25rem;
}
.mission-launcher-info p {
  color: var(--gray-600);
  font-size: 0.9rem;
  margin: 0;
  line-height: 1.5;
}
.mission-launcher-btn {
  flex-shrink: 0;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--db-cyan);
  color: white;
  padding: 10px 18px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
  white-space: nowrap;
  transition: background 0.15s;
}
.mission-launcher-btn:hover { background: #0090c0; }

@media (max-width: 640px) {
  .mission-launcher { flex-direction: column; align-items: stretch; text-align: left; }
  .mission-launcher-btn { justify-content: center; }
}

/* ─── Responsive ────────────────────────────────────────────── */

@media (max-width: 640px) {
  h1 { font-size: 1.5rem; }
  .article-container { padding: 32px 16px 64px; }
  h2 { font-size: 1.15rem; margin-top: 36px; }
  .video-wrapper.sticky { width: 260px; bottom: 10px; right: 10px; }
  .code-comparison { grid-template-columns: 1fr; }
  .picker-scenes { flex-direction: column; }
  .picker-shapes { grid-template-columns: repeat(2, 1fr); }
  .picker-launch { flex-direction: column; gap: 12px; text-align: center; }
  .lesson-nav { grid-template-columns: 1fr; }
  .feature-grid { grid-template-columns: 1fr; gap: 12px; }
}

/* ── Utility components (callouts, spec tables, captions, key/detail lists) ── */

.callout {
  position: relative;
  padding: 16px 18px 16px 50px;
  margin: 24px 0;
  border-radius: 10px;
  border-left: 4px solid var(--db-cyan);
  background: var(--gray-50);
  color: var(--gray-700);
  font-size: 0.95rem;
  line-height: 1.6;
}
.callout::before { position: absolute; left: 16px; top: 15px; font-size: 1.1rem; line-height: 1.5; }
.callout strong { color: var(--gray-900); }
.callout-info { border-left-color: var(--db-cyan); background: #eff8fd; }
.callout-info::before { content: "ℹ️"; }
.callout-warning { border-left-color: var(--db-orange); background: #fdf3ee; }
.callout-warning::before { content: "⚠️"; }
.callout-danger { border-left-color: #dc2626; background: #fef2f2; }
.callout-danger::before { content: "🛑"; }
.callout-tip { border-left-color: var(--db-green); background: #ecfdf5; }
.callout-tip::before { content: "💡"; }
.callout-mistake { border-left-color: var(--db-orange); background: #fff7ed; }
.callout-mistake::before { content: "✗"; color: var(--db-orange); font-weight: 700; }

/* Wide tables scroll inside their own wrapper rather than pushing the page
   sideways at 430px. Optional — a table narrow enough to fit needs no wrap. */
.table-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.table-wrap .spec-table { min-width: 520px; }

.spec-table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  font-size: 0.95rem;
  border: 1px solid var(--gray-200);
  border-radius: 10px;
  overflow: hidden;
}
.spec-table thead th {
  background: var(--db-navy);
  color: #fff;
  text-align: left;
  font-weight: 600;
  padding: 10px 14px;
  font-size: 0.85rem;
}
.spec-table td {
  padding: 10px 14px;
  border-top: 1px solid var(--gray-200);
  vertical-align: top;
}
.spec-table tbody tr:nth-child(even) { background: var(--gray-50); }
.spec-table td:first-child { white-space: nowrap; }

/* Content images — opt-in class so the rule can't touch inline chips/thumbs.
   Bound tightly to the caption below it; standard block gap above/below the pair. */
.article-img {
  display: block;
  max-width: 100%;
  height: auto;
  margin: var(--space-block) auto 0;
  border-radius: 12px;
}
.article-img + .caption { margin-top: 10px; }

.caption {
  margin: 10px auto var(--space-block);
  max-width: 600px;
  font-size: 0.85rem;
  color: var(--gray-500);
  line-height: 1.5;
  text-align: center;
}

/* Key / detail list — organized alternative to loose bullets */
.kv-list {
  list-style: none;
  padding: 0;
  margin: 24px 0;
  border: 1px solid var(--gray-200);
  border-radius: 10px;
  overflow: hidden;
}
.kv-list li {
  display: grid;
  grid-template-columns: 190px 1fr;
  gap: 20px;
  padding: 14px 18px;
  border-top: 1px solid var(--gray-200);
}
.kv-list li:first-child { border-top: none; }
.kv-list li:nth-child(even) { background: var(--gray-50); }
.kv-list .kv-key { font-weight: 700; color: var(--db-navy); }
.kv-list .kv-val { color: var(--gray-700); line-height: 1.55; }
@media (max-width: 640px) {
  .kv-list li { grid-template-columns: 1fr; gap: 4px; }
}

/* Step list — numbered, with a connecting timeline (for ordered sequences) */
ol.steps {
  list-style: none;
  counter-reset: step;
  padding: 0;
  margin: 24px 0;
}
ol.steps > li {
  position: relative;
  padding: 3px 0 3px 48px;
  margin-bottom: 18px;
  line-height: 1.6;
  color: var(--gray-700);
}
ol.steps > li:last-child { margin-bottom: 0; }
ol.steps > li::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  left: 0;
  top: 0;
  width: 30px;
  height: 30px;
  border-radius: 50%;
  background: var(--db-navy);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.9rem;
}
ol.steps > li:not(:last-child)::after {
  content: "";
  position: absolute;
  left: 14px;
  top: 34px;
  bottom: -18px;
  width: 2px;
  background: var(--gray-200);
}
ol.steps > li strong { color: var(--gray-900); }
/* Nested sub-points inside a step: normal bullets, indented, not step-numbered */
ol.steps > li ul {
  list-style: disc;
  padding-left: 1.4rem;
  margin: 8px 0 0;
}
ol.steps > li ul li { margin-bottom: 4px; line-height: 1.6; }

/* Feature-card bullet lists (Hardware / Tools required) — indent off the card edge */
.feature-card ul { padding-left: 1.4rem; margin: 4px 0 0; }
.feature-card li { margin-bottom: 4px; line-height: 1.55; }

/* Checklist — round check markers (for verification / pre-flight lists) */
ul.checklist {
  list-style: none;
  padding: 0;
  margin: 24px 0;
}
ul.checklist li {
  position: relative;
  padding: 2px 0 2px 34px;
  margin-bottom: 12px;
  line-height: 1.6;
  color: var(--gray-700);
}
ul.checklist li:last-child { margin-bottom: 0; }
ul.checklist li::before {
  content: "✓";
  position: absolute;
  left: 0;
  top: 1px;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--db-green);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 700;
}

/* ─── Code blocks ───────────────────────────────────────────────
   Lives here, not in a per-article <style>, because the lesson page
   (pages/[track]/courses/[id]/[lesson].vue) extracts only the <article>
   element and loads this stylesheet — anything in an article's own <head>
   is dropped, so styles defined there work standalone and vanish in the
   course. Three articles had each redefined this block; consolidating it
   makes all of them render inside a lesson too. */
pre.code-block {
  background: var(--gray-900);
  color: #e5e7eb;
  border-radius: 10px;
  padding: 20px 24px;
  margin: 16px 0;
  overflow-x: auto;
  font-family: 'SF Mono', SFMono-Regular, Consolas, monospace;
  font-size: 0.85rem;
  line-height: 1.7;
}
pre.code-block .comment  { color: #6b7280; }
pre.code-block .prompt   { color: #fbbf24; }
pre.code-block .path     { color: #93c5fd; }
pre.code-block .ok       { color: #86efac; }
pre.code-block .err      { color: #fca5a5; }
pre.code-block .keyword  { color: #c084fc; }
pre.code-block .string   { color: #86efac; }
pre.code-block .function { color: #93c5fd; }
pre.code-block .builtin  { color: #fbbf24; }
pre.code-block .number   { color: #f9a8d4; }

/* ─── Download links ────────────────────────────────────────────
   A file or tool to go and fetch, as its own row: bold name, then a
   monospace-ish detail line. Used by the DEXI-3 Configuration course for
   QGroundControl, the DEXI OS image, and the firmware/parameter files. */
.dl {
  display: block;
  margin-bottom: 10px;
  padding: 14px 16px;
  background: #fff;
  border: 1px solid var(--gray-200);
  border-left: 4px solid var(--db-cyan);
  border-radius: 0 10px 10px 0;
  text-decoration: none;
}
.dl:hover { background: var(--gray-50); }
.dl b {
  display: block;
  color: var(--db-navy);
  font-size: 0.95rem;
  margin-bottom: 2px;
}
.dl span {
  color: var(--gray-500);
  font-size: 0.82rem;
  line-height: 1.5;
  word-break: break-word;
}

/* ─── Numbered step headings ────────────────────────────────────
   A step's number as a chip in front of its <h3>, for procedures where the
   order is the point and a bare heading sequence would not say so. */
.step-n {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  margin-right: 8px;
  vertical-align: -4px;
  border-radius: 50%;
  background: var(--db-cyan);
  color: #fff;
  font-size: 0.82rem;
  font-weight: 800;
  line-height: 1;
}

/* ─── Which-kit badges ──────────────────────────────────────────
   Marks a step as applying to one kit rather than every drone. */
.kit {
  display: inline-block;
  vertical-align: middle;
  margin-left: 6px;
  padding: 2px 8px;
  border-radius: 20px;
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.04em;
}
.kit-dev { background: #dbeafe; color: #1d4ed8; }
.kit-all { background: #dcfce7; color: #15803d; }

/* ─── Inline SVG diagrams ───────────────────────────────────────
   The SVG carries its own <style>, namespaced under .prop-fig so its short
   class names cannot leak into the page. */
.prop-fig { margin: 24px 0 8px; }
.prop-fig svg { width: 100%; height: auto; display: block; }

/* Opt-in variant for a table whose first column holds a sentence rather than
   a short label. The default nowrap is right for a parameter list and wrong
   here — it pushes the table past its wrapper and forces a sideways scroll to
   reach column two. */
.table-wrap--prose .spec-table td:first-child { white-space: normal; }