:root {
  color-scheme: dark;
  --bg: #03111c;
  --bg-deep: #010914;
  --panel: rgba(3, 14, 27, 0.9);
  --panel-soft: rgba(9, 29, 45, 0.72);
  --line: rgba(122, 193, 255, 0.18);
  --line-strong: rgba(125, 237, 213, 0.42);
  --text: #eaf3ff;
  --muted: #94a9bf;
  --cyan: #57f0d4;
  --red: #d93451;
  --amber: #ffc857;
  --shadow: 0 24px 80px rgba(0, 0, 0, 0.44);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, system-ui, sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 18% 15%, rgba(30, 115, 104, 0.34), transparent 30rem),
    radial-gradient(circle at 82% 12%, rgba(17, 86, 142, 0.35), transparent 32rem),
    linear-gradient(115deg, #082323 0%, var(--bg-deep) 45%, #092136 100%);
}

body::before {
  position: fixed;
  inset: 0;
  z-index: -1;
  content: "";
  background-image:
    linear-gradient(rgba(114, 184, 255, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(114, 184, 255, 0.035) 1px, transparent 1px);
  background-size: 48px 48px;
}

button,
input {
  font: inherit;
}

button,
a {
  cursor: pointer;
}

a {
  color: inherit;
  text-decoration: none;
}

.course-shell {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 32px 0 72px;
}

.course-topbar,
.hero-panel,
.lesson-panel,
.lesson-list,
.certificate-panel,
.status-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  background:
    linear-gradient(135deg, rgba(8, 26, 43, 0.98), rgba(1, 9, 20, 0.95)),
    var(--panel);
  box-shadow: var(--shadow), inset 0 1px 0 rgba(255, 255, 255, 0.03);
}

.course-topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 24px;
  padding: 12px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
}

.brand-mark {
  display: grid;
  width: 44px;
  height: 44px;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  font-family: "JetBrains Mono", monospace;
  font-weight: 800;
  color: var(--cyan);
  background: rgba(87, 240, 212, 0.12);
  text-transform: uppercase;
}

.brand strong,
.brand small {
  display: block;
}

.brand small {
  margin-top: 2px;
  font-family: "JetBrains Mono", monospace;
  font-size: 0.62rem;
  color: var(--muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

nav a,
.lesson-tab,
.primary-action,
.secondary-action,
.check-option {
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--text);
  background: rgba(16, 37, 58, 0.6);
}

nav a {
  display: grid;
  place-items: center;
  padding: 0 14px;
  color: #bdd0e5;
}

.hero-panel {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) 330px;
  gap: 24px;
  padding: clamp(28px, 5vw, 56px);
}

.eyebrow {
  margin: 0 0 14px;
  font-family: "JetBrains Mono", monospace;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--cyan);
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 780px;
  margin-bottom: 20px;
  font-size: clamp(3rem, 7vw, 6.4rem);
  line-height: 0.95;
}

h2 {
  margin-bottom: 18px;
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 1;
}

.hero-copy,
.lesson-panel p,
.status-card li,
.certificate-panel p {
  color: var(--muted);
  line-height: 1.7;
}

.hero-copy {
  max-width: 700px;
  font-size: 1.05rem;
}

.hero-actions,
.lesson-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 24px;
}

.primary-action,
.secondary-action {
  padding: 0 20px;
  font-weight: 800;
}

.primary-action {
  border-color: rgba(255, 73, 104, 0.45);
  background: linear-gradient(180deg, rgba(201, 35, 64, 0.94), rgba(118, 18, 37, 0.94));
  box-shadow: 0 16px 40px rgba(217, 52, 81, 0.2);
}

.status-card {
  padding: 22px;
  background: rgba(2, 13, 27, 0.72);
}

.status-card ul {
  display: grid;
  gap: 10px;
  margin: 20px 0 0;
  padding-left: 18px;
}

.progress-meter span {
  display: block;
  margin-bottom: 10px;
  font-family: "JetBrains Mono", monospace;
  color: var(--amber);
}

.progress-meter div {
  height: 9px;
  border-radius: 999px;
  background: rgba(125, 237, 213, 0.12);
  overflow: hidden;
}

.progress-meter i {
  display: block;
  width: 0%;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--cyan), var(--blue));
  transition: width 0.25s ease;
}

.course-layout {
  display: grid;
  grid-template-columns: 290px minmax(0, 1fr);
  gap: 18px;
  margin-top: 26px;
}

.lesson-list {
  display: grid;
  align-self: start;
  gap: 8px;
  max-height: calc(100vh - 120px);
  overflow: auto;
  padding: 12px;
  position: sticky;
  top: 16px;
}

.lesson-tab {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px;
  text-align: left;
}

.lesson-tab span {
  display: grid;
  width: 36px;
  height: 30px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 8px;
  font-family: "JetBrains Mono", monospace;
  color: var(--cyan);
}

.lesson-tab.active,
.lesson-tab.complete {
  border-color: var(--line-strong);
  background: rgba(41, 112, 123, 0.42);
}

.lesson-panel {
  min-height: 590px;
  padding: clamp(24px, 4vw, 42px);
}

.lesson-panel ul {
  display: grid;
  gap: 12px;
  margin: 18px 0;
  padding-left: 20px;
  color: #c4d5e8;
  line-height: 1.65;
}

.rule-card,
.scenario-card,
.check-card,
.activity-card {
  margin: 18px 0;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel-soft);
}

.rule-card strong {
  color: var(--cyan);
}

.check-options {
  display: grid;
  gap: 10px;
  margin-top: 14px;
}

.check-option {
  padding: 12px 14px;
  text-align: left;
}

.check-option.correct {
  border-color: rgba(87, 240, 212, 0.75);
  background: rgba(87, 240, 212, 0.14);
}

.check-option.wrong {
  border-color: rgba(217, 52, 81, 0.75);
  background: rgba(217, 52, 81, 0.14);
}

.feedback {
  margin-top: 12px;
  font-weight: 800;
  color: var(--amber);
}

.intel-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin: 18px 0;
}

.intel-grid details {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
  background: rgba(2, 13, 27, 0.68);
}

.intel-grid summary {
  font-weight: 800;
  color: var(--text);
  cursor: pointer;
}

.intel-grid p {
  margin: 12px 0 0;
}

.sort-source,
.sequence-grid {
  display: grid;
  gap: 10px;
  margin: 16px 0;
}

.drag-chip,
.sequence-step {
  min-height: 48px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px 14px;
  color: var(--text);
  text-align: left;
  background: rgba(1, 9, 20, 0.72);
}

.drag-chip {
  cursor: grab;
}

.drag-chip:active {
  cursor: grabbing;
}

.bucket-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin: 16px 0;
}

.drop-bucket {
  min-height: 180px;
  border: 1px dashed rgba(125, 237, 213, 0.38);
  border-radius: 8px;
  padding: 14px;
  background: rgba(2, 13, 27, 0.58);
}

.drop-bucket h4 {
  margin: 0 0 12px;
  font-family: "JetBrains Mono", monospace;
  font-size: 0.78rem;
  color: var(--cyan);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.drop-bucket .drag-chip {
  width: 100%;
  margin-bottom: 8px;
}

.drag-chip.correct,
.sequence-step.selected,
.check-option.correct {
  border-color: rgba(87, 240, 212, 0.75);
  background: rgba(87, 240, 212, 0.14);
}

.drag-chip.wrong {
  border-color: rgba(217, 52, 81, 0.75);
  background: rgba(217, 52, 81, 0.14);
}

.sequence-answer {
  min-height: 44px;
  margin: 12px 0;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px 14px;
  font-family: "JetBrains Mono", monospace;
  color: var(--cyan);
  background: rgba(1, 9, 20, 0.72);
}

.certificate-panel {
  display: grid;
  grid-template-columns: 1fr 330px;
  gap: 22px;
  margin-top: 26px;
  padding: clamp(24px, 4vw, 36px);
}

.certificate-card {
  display: grid;
  min-height: 220px;
  align-content: center;
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  padding: 22px;
  background: rgba(87, 240, 212, 0.08);
}

.certificate-card h3 {
  margin-bottom: 22px;
  font-size: 1.7rem;
}

.certificate-card span {
  color: var(--muted);
}

@media (max-width: 880px) {
  .course-topbar,
  .hero-panel,
  .course-layout,
  .certificate-panel,
  .intel-grid,
  .bucket-grid {
    grid-template-columns: 1fr;
  }

  .course-topbar {
    display: grid;
  }

  .lesson-list {
    max-height: none;
    position: static;
  }
}

@media (max-width: 600px) {
  .course-shell {
    width: min(100% - 20px, 1120px);
    padding-top: 10px;
  }

  h1 {
    font-size: clamp(2.6rem, 14vw, 4rem);
  }
}