:root {
  color-scheme: light;
  --ink: #16324f;
  --muted: #5c6d80;
  --teal: #087f8c;
  --teal-dark: #06616b;
  --purple: #7556d8;
  --page: #f3f7fc;
  --surface: #ffffff;
  --border: #dce5ef;
  --success: #18794e;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--page);
  color: var(--ink);
  font-family: Inter, Arial, sans-serif;
  line-height: 1.65;
}

a {
  color: var(--teal-dark);
}

button,
textarea {
  font: inherit;
}

button:focus-visible,
a:focus-visible,
textarea:focus-visible,
input:focus-visible {
  outline: 3px solid #e6a23c;
  outline-offset: 3px;
}

.course-header {
  min-height: 76px;
  padding: 16px max(5%, calc((100% - 1160px) / 2));
  background: #102a43;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.brand {
  color: white;
  text-decoration: none;
  font-size: 1.2rem;
  font-weight: 800;
}

.brand > span:last-child {
  color: #69e2d0;
}

.brand-icon {
  display: inline-grid;
  place-items: center;
  margin-right: 8px;
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: #087f8c;
  color: white;
}

.back-link {
  color: #e0f2fe;
  text-decoration: none;
  font-weight: 600;
}

.back-link:hover,
.course-footer a:hover,
.text-link:hover {
  text-decoration: underline;
}

main {
  width: min(1120px, 90%);
  margin: 0 auto;
}

.hero {
  margin: 32px 0;
  padding: clamp(28px, 6vw, 66px);
  border-radius: 28px;
  color: white;
  background: linear-gradient(125deg, #102a43, #087f8c 70%, #36a99b);
  box-shadow: 0 14px 34px #102a4317;
}

.eyebrow,
.step-label {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.1em;
}

.eyebrow {
  color: #a7f3e8;
}

.hero h1 {
  margin: 12px 0;
  font-size: clamp(2.2rem, 6vw, 4rem);
  line-height: 1.1;
}

.hero h1 span {
  color: #a7f3e8;
}

.hero > p {
  max-width: 680px;
  font-size: 1.1rem;
  color: #f0fdfa;
}

.hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 24px;
}

.hero-tags span {
  padding: 7px 12px;
  border: 1px solid #ffffff50;
  border-radius: 999px;
  background: #ffffff12;
  font-size: 0.9rem;
}

.lesson-card,
.finish-card {
  margin: 24px 0;
  padding: clamp(22px, 4vw, 38px);
  border: 1px solid var(--border);
  border-radius: 22px;
  background: var(--surface);
  box-shadow: 0 8px 28px #102a4308;
}

.step-label {
  color: var(--teal);
}

.lesson-card h2,
.finish-card h2 {
  margin: 8px 0;
  font-size: clamp(1.5rem, 3vw, 2rem);
  line-height: 1.25;
}

.lesson-card > p,
.finish-card > p {
  color: var(--muted);
}

.concept-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin: 24px 0;
}

.concept {
  padding: 22px;
  border-radius: 16px;
}

.html-concept {
  background: #fff1e8;
}

.css-concept {
  background: #f0ebff;
}

.concept-icon {
  font-size: 2rem;
}

.concept h3 {
  margin: 8px 0 4px;
}

.concept p {
  margin: 0;
  color: #46576a;
}

.example-box {
  padding: 18px 20px;
  border-left: 5px solid #e5a43b;
  border-radius: 10px;
  background: #fff9e9;
}

.example-box p {
  margin: 4px 0 0;
}

.editor-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 20px;
  margin-top: 24px;
  align-items: start;
}

.editor-panel,
.preview-panel {
  min-width: 0;
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: #f8fafc;
}

.editor-panel {
  padding: 18px;
}

.editor-panel label {
  display: block;
  margin: 8px 0;
  font-weight: 800;
}

.editor-panel textarea {
  display: block;
  width: 100%;
  min-height: 180px;
  resize: vertical;
  padding: 14px;
  border: 1px solid #314b67;
  border-radius: 10px;
  background: #102a43;
  color: #e0f2fe;
  font-family: "Courier New", monospace;
  font-size: 0.88rem;
  line-height: 1.6;
  tab-size: 2;
}

.editor-panel textarea:first-of-type {
  min-height: 150px;
}

.editor-help,
.preview-note {
  color: var(--muted);
  font-size: 0.82rem;
}

.editor-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 18px;
}

.button {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  min-height: 44px;
  padding: 10px 16px;
  border: 0;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 800;
  text-align: center;
  text-decoration: none;
  transition: transform 0.15s ease, background 0.15s ease;
}

.button:hover {
  transform: translateY(-1px);
}

.button-primary {
  background: var(--teal);
  color: white;
}

.button-primary:hover {
  background: var(--teal-dark);
}

.button-secondary {
  border: 1px solid var(--border);
  background: white;
  color: var(--ink);
}

.editor-message {
  min-height: 24px;
  margin-bottom: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.preview-heading {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 14px;
  border-bottom: 1px solid var(--border);
  background: white;
}

.preview-heading strong {
  margin-left: 8px;
  font-size: 0.9rem;
}

.preview-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #f59e0b;
}

.preview-dot:nth-child(2) {
  background: #34d399;
}

.preview-dot:nth-child(3) {
  background: #f87171;
}

#website-preview {
  display: block;
  width: 100%;
  min-height: 350px;
  border: 0;
  background: white;
}

.preview-note {
  padding: 0 14px 12px;
}

.quiz-question {
  margin: 20px 0;
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 12px;
}

.quiz-question legend {
  padding: 0 6px;
  font-weight: 800;
}

.quiz-question label {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  margin: 10px 0;
  cursor: pointer;
}

.quiz-question input {
  margin-top: 6px;
  accent-color: var(--teal);
}

code {
  padding: 2px 6px;
  border-radius: 5px;
  background: #edf2f7;
  color: #803c9c;
}

.quiz-result {
  min-height: 28px;
  font-weight: 800;
}

.quiz-result.success {
  color: var(--success);
}

.quiz-result.retry {
  color: #a65312;
}

.finish-card {
  text-align: center;
  background: linear-gradient(145deg, #e6fffa, #f1f5ff);
}

.finish-icon {
  font-size: 3rem;
}

.finish-card > p {
  max-width: 650px;
  margin: 12px auto 22px;
}

.finish-card .button {
  margin: 4px;
}

.text-link {
  display: block;
  margin-top: 14px;
  font-weight: 700;
}

.course-footer {
  padding: 26px 5%;
  background: #102a43;
  color: #e0f2fe;
  text-align: center;
}

.course-footer p {
  margin: 4px 0;
}

.course-footer a {
  color: #a7f3e8;
}

@media (max-width: 760px) {
  .course-header {
    align-items: flex-start;
    flex-direction: column;
  }

  .concept-grid,
  .editor-grid {
    grid-template-columns: 1fr;
  }

  .hero {
    border-radius: 18px;
  }

  #website-preview {
    min-height: 300px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition: none !important;
  }
}