:root {
  --brand: #0f4c5c;
  --brand-accent: #2b8c82;
  --accent: #f0a202;
  --bg: #f8f6f2;
  --bg-alt: #eef4f4;
  --text: #1f2933;
  --muted: #4b5b66;
  --card: #ffffff;
  --border: #d9d5ce;
  --shadow: 0 12px 30px rgba(31, 41, 51, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Source Sans 3", "Trebuchet MS", "Segoe UI", sans-serif;
  font-size: 18px;
  line-height: 1.65;
  color: var(--text);
  background: linear-gradient(180deg, var(--bg) 0%, var(--bg-alt) 100%);
}

img,
video {
  max-width: 100%;
  height: auto;
}

.container-fluid {
  max-width: 1100px;
  margin: 0 auto;
  padding: 32px 24px 64px;
}

.row {
  margin: 0;
}

.banner-img {
  margin-bottom: 20px;
}

.banner-img img {
  width: 100%;
  border-radius: 16px;
  box-shadow: var(--shadow);
}

h1,
h2,
h3,
h4 {
  font-family: "Merriweather", "Georgia", serif;
  color: var(--brand);
}

h1 {
  font-size: 2.3rem;
  margin: 0 0 16px;
}

h2 {
  font-size: 1.6rem;
  margin: 32px 0 12px;
}

h3 {
  font-size: 1.3rem;
  margin: 24px 0 8px;
}

p {
  margin: 0 0 1rem;
}

hr {
  border: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--border), transparent);
  margin: 24px 0;
}

ul,
ol {
  padding-left: 1.25rem;
}

ul[style*="list-style-type: none"],
ul[role="list"] {
  list-style: none;
  padding-left: 0;
}

ul[role="list"] li {
  margin-bottom: 0.35rem;
}

a {
  color: var(--brand);
}

a:hover {
  color: var(--brand-accent);
}

footer {
  margin-top: 32px;
  text-align: center;
}

footer img {
  max-width: 220px;
}

.course-index {
  background: #f4f6f7;
}

.course-hero {
  position: relative;
  min-height: 320px;
  background-image: url("atc%20building.png");
  background-size: cover;
  background-position: center;
  color: #ffffff;
}

.course-hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(120deg, rgba(15, 76, 92, 0.85), rgba(15, 76, 92, 0.35));
}

.course-hero-content {
  position: relative;
  max-width: 900px;
  padding: 48px 24px 56px;
  margin: 0 auto;
}

.course-hero-kicker {
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.85rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.course-hero h1 {
  color: #ffffff;
  font-size: 2.6rem;
  margin-bottom: 12px;
  font-family: "Merriweather", "Georgia", serif;
}

.course-hero-subtitle {
  max-width: 520px;
  margin-bottom: 20px;
  color: rgba(255, 255, 255, 0.85);
}

.course-summary {
  margin-top: -32px;
  background: #ffffff;
  border-radius: 18px;
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
}

.course-brand img {
  max-width: 140px;
}

.course-progress {
  margin-top: 16px;
}

.course-progress-label {
  display: flex;
  justify-content: space-between;
  font-weight: 600;
  margin-bottom: 6px;
}

.course-progress-track {
  height: 8px;
  border-radius: 999px;
  background: rgba(15, 76, 92, 0.12);
  overflow: hidden;
}

.course-progress-fill {
  height: 100%;
  width: 0%;
  background: var(--brand-accent);
  transition: width 0.3s ease;
}

.course-outline {
  margin-top: 32px;
}

.course-section {
  margin-bottom: 20px;
}

.course-section-title {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 10px;
}

.course-shell-body {
  background: #f4f6f7;
}

.course-shell {
  display: flex;
  min-height: 100vh;
  background: #f4f6f7;
}

.course-sidebar {
  width: 300px;
  background: #f8f9fb;
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}

.course-main {
  flex: 1;
}

.course-shell .container-fluid {
  max-width: 1020px;
  padding: 32px 32px 64px;
}

.sidebar-hero {
  position: relative;
  min-height: 180px;
  background-image: url("atc%20building.png");
  background-size: cover;
  background-position: center;
  color: #ffffff;
}

.sidebar-hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(15, 76, 92, 0.9), rgba(15, 76, 92, 0.4));
}

.sidebar-hero-content {
  position: relative;
  padding: 20px 18px 18px;
}

.sidebar-hero-title {
  font-weight: 700;
  font-size: 1rem;
}

.sidebar-hero-subtitle {
  font-size: 0.9rem;
  line-height: 1.3;
  margin-top: 4px;
}

.sidebar-progress {
  margin-top: 12px;
}

.sidebar-progress-value {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.sidebar-progress-track {
  height: 6px;
  margin-top: 6px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.25);
  overflow: hidden;
}

.sidebar-progress-fill {
  height: 100%;
  width: 0%;
  background: #ffffff;
  opacity: 0.9;
}

.course-sidebar .course-reset-button {
  margin-top: 12px;
  width: 100%;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  background: rgba(255, 255, 255, 0.2);
  color: #ffffff;
  border-color: rgba(255, 255, 255, 0.4);
}

.sidebar-nav {
  padding: 16px 12px 24px;
}

.course-sidebar .course-section-title {
  color: var(--muted);
  font-size: 0.7rem;
  margin: 16px 8px 6px;
}

.course-sidebar .course-toc {
  gap: 6px;
}

.course-sidebar .course-row {
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid transparent;
  background: transparent;
}

.course-sidebar .course-row.is-active {
  border-color: rgba(15, 76, 92, 0.2);
  background: rgba(15, 76, 92, 0.08);
}

.course-sidebar .course-row-title::before {
  width: 8px;
  height: 8px;
}

.course-sidebar .course-status {
  width: 14px;
  height: 14px;
}

.course-intro p {
  margin-bottom: 0.75rem;
}

.course-start {
  margin: 20px 0 28px;
}

.course-start-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  border-radius: 999px;
  background: var(--brand);
  color: #ffffff;
  font-weight: 700;
  text-decoration: none;
  box-shadow: var(--shadow);
}

.course-reset-button {
  margin-top: 12px;
  border: 1px solid rgba(15, 76, 92, 0.3);
  background: transparent;
  color: var(--brand);
  font-weight: 600;
  padding: 8px 14px;
  border-radius: 999px;
  cursor: pointer;
}

.course-toc {
  list-style: none;
  padding-left: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.course-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 12px 16px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: #ffffff;
}

.course-link {
  text-decoration: none;
  color: var(--brand);
  font-weight: 600;
  flex: 1;
}

.course-row-title {
  display: inline-flex;
  align-items: center;
  gap: 12px;
}

.course-row-title::before {
  content: "";
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: rgba(15, 76, 92, 0.2);
  display: inline-block;
}

.course-status {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  border: 2px solid rgba(15, 76, 92, 0.3);
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.course-row.course-complete .course-status {
  border-color: var(--brand-accent);
  background: var(--brand-accent);
  position: relative;
}

.course-row.course-complete .course-status::after {
  content: "";
  width: 6px;
  height: 3px;
  border-left: 2px solid #ffffff;
  border-bottom: 2px solid #ffffff;
  transform: rotate(-45deg);
  margin-top: -1px;
}

.course-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: space-between;
  align-items: center;
  margin: 24px 0 12px;
  padding: 12px 16px;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: var(--card);
  box-shadow: var(--shadow);
}

.course-nav-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 8px 16px;
  border-radius: 999px;
  background: rgba(15, 76, 92, 0.12);
  color: var(--brand);
  font-weight: 700;
  text-decoration: none;
}

.course-nav-link.course-nav-disabled {
  opacity: 0.5;
  pointer-events: none;
}

.course-nav-link.course-nav-next {
  background: var(--brand);
  color: #ffffff;
}

.course-nav-disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.course-nav-note {
  width: 100%;
  font-size: 0.95rem;
  color: var(--muted);
}

.sr-only {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.course-element,
.course-practice,
.hotspot,
.tabs-wrapper,
.accordion,
.flip-card-wrapper {
  margin: 16px 0 24px;
}

.course-practice {
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--card);
  padding: 16px;
  box-shadow: var(--shadow);
}

.course-practice .placeholder {
  padding: 12px 16px;
  border-radius: 12px;
  background: rgba(15, 76, 92, 0.08);
  color: var(--brand);
  font-weight: 600;
  margin-bottom: 12px;
}

.course-practice iframe {
  width: 100%;
  min-height: 320px;
  border: 1px solid var(--border);
  border-radius: 12px;
}

.practice-card {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.practice-header {
  display: flex;
  justify-content: flex-start;
}

.practice-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 12px;
  border-radius: 999px;
  background: rgba(15, 76, 92, 0.12);
  color: var(--brand);
  font-weight: 700;
  font-size: 0.85rem;
}

.practice-body {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.practice-question {
  font-weight: 600;
}

.practice-form {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.practice-option {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: #ffffff;
}

.practice-option input {
  margin-top: 4px;
}

.practice-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.practice-submit,
.practice-reset {
  border: none;
  padding: 10px 18px;
  border-radius: 10px;
  font-weight: 700;
  cursor: pointer;
}

.practice-submit {
  background: var(--brand);
  color: #ffffff;
}

.practice-reset {
  background: rgba(15, 76, 92, 0.12);
  color: var(--brand);
}

.practice-feedback {
  padding: 10px 12px;
  border-radius: 12px;
  background: rgba(31, 41, 51, 0.06);
  color: var(--text);
}

.practice-feedback:empty {
  display: none;
}

.practice-feedback-correct {
  background: rgba(43, 140, 130, 0.18);
  color: #0b3f39;
}

.practice-feedback-incorrect {
  background: rgba(221, 107, 0, 0.18);
  color: #6b3a00;
}

.practice-feedback-warning {
  background: rgba(240, 162, 2, 0.18);
  color: #6b3a00;
}

.practice-message {
  margin: 0;
}

.card,
.jumbotron {
  border-radius: 16px;
  border: 1px solid var(--border);
  background: var(--card);
  box-shadow: var(--shadow);
}

.card-standard,
.card-graphic,
.jumbotron {
  border-left: 6px solid var(--accent);
  padding: 16px;
}

.card-graphic .card-body {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.card-icon {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--accent);
  flex: 0 0 auto;
}

.callout-title {
  font-weight: 700;
  color: var(--brand);
  margin-bottom: 8px;
}

.jumbotron {
  background: linear-gradient(135deg, rgba(15, 76, 92, 0.08), rgba(240, 162, 2, 0.1));
}

.accordion .card {
  margin-bottom: 12px;
  overflow: hidden;
}

.accordion .card-header {
  padding: 12px 16px;
  background: rgba(15, 76, 92, 0.08);
  cursor: pointer;
  position: relative;
}

.accordion .card-header::after {
  content: "+";
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-weight: 700;
  color: var(--brand);
}

.accordion .card-header[aria-expanded="true"]::after {
  content: "–";
}

.accordion .card-title {
  font-weight: 600;
  margin: 0;
}

.collapse {
  display: none;
}

.collapse.show {
  display: block;
}

.tabs-wrapper .list-group {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tabs-wrapper .list-group-item {
  cursor: pointer;
  border-radius: 999px;
  border: 1px solid var(--border);
  padding: 10px 18px;
  margin: 0;
  background: #ffffff;
  color: var(--brand);
  font-weight: 600;
  text-decoration: none;
}

.tabs-wrapper .list-group-item.active {
  background: var(--brand);
  color: #ffffff;
  border-color: var(--brand);
}

.tab-content {
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--card);
  padding: 16px;
  margin-top: 16px;
  box-shadow: var(--shadow);
}

.tab-pane {
  display: none;
}

.tab-pane.active {
  display: block;
}

.flip-card-set {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
}

.flip-card-content {
  cursor: pointer;
}

.flip-card-front,
.flip-card-back {
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 16px;
  background: var(--card);
  box-shadow: var(--shadow);
}

.flip-card-back {
  display: none;
}

.flip-card-content.is-flipped .flip-card-front {
  display: none;
}

.flip-card-content.is-flipped .flip-card-back {
  display: block;
}

.flip-icon {
  margin-top: 12px;
  font-size: 0.85rem;
  color: var(--muted);
}

.timeline {
  list-style: none;
  padding-left: 0;
  position: relative;
}

.timeline::before {
  content: "";
  position: absolute;
  left: 12px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--border);
}

.timeline li {
  position: relative;
  padding-left: 40px;
  margin-bottom: 24px;
}

.timeline-badge {
  position: absolute;
  left: 4px;
  top: 6px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--brand-accent);
}

.timeline-panel {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 16px;
  background: var(--card);
  box-shadow: var(--shadow);
}

.timeline-heading {
  font-weight: 700;
  color: var(--brand);
  margin-bottom: 6px;
}

.timeline-title {
  font-weight: 700;
}

.layout {
  display: flex;
  flex-wrap: wrap;
  gap: 24px;
  align-items: center;
  margin-bottom: 24px;
}

.layout-column {
  flex: 1 1 280px;
}

.hotspot-container {
  position: relative;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: var(--shadow);
}

.hotspot-marker {
  position: absolute;
  transform: translate(-50%, -50%);
  width: 28px;
  height: 28px;
  border-radius: 50%;
  border: 2px solid #ffffff;
  background: var(--accent);
  color: #ffffff;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.2);
}

.hotspot-popover {
  position: absolute;
  transform: translate(-50%, 12px);
  padding: 12px;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 12px;
  width: min(260px, 90vw);
  box-shadow: var(--shadow);
  z-index: 10;
}

.hotspot-list {
  margin: 16px 0 0;
  padding-left: 1rem;
}

.hotspot-list li {
  margin-bottom: 8px;
}

.video-wrapper video {
  width: 100%;
  border-radius: 12px;
  box-shadow: var(--shadow);
}

@media (max-width: 768px) {
  body {
    font-size: 16px;
  }

  .container-fluid {
    padding: 24px 16px 48px;
  }

  h1 {
    font-size: 2rem;
  }

  .course-hero-content {
    padding: 36px 20px 44px;
  }

  .course-hero h1 {
    font-size: 2rem;
  }

  .course-summary {
    margin-top: -20px;
  }

  .course-shell {
    flex-direction: column;
  }

  .course-sidebar {
    width: 100%;
    height: auto;
    position: relative;
  }

  .course-shell .container-fluid {
    padding: 24px 16px 48px;
  }
}