:root {
  --bg: #eef2f8;
  --bg-soft: #f8faff;
  --surface: #ffffff;
  --text: #172033;
  --muted: #5f6b82;
  --border: #d6deea;
  --primary: #114b7a;
  --primary-dark: #0a3558;
  --accent: #0f8a7f;
  --radius-sm: 10px;
  --radius-md: 14px;
  --radius-lg: 18px;
  --shadow-soft: 0 8px 24px rgba(15, 23, 42, 0.07);
  --shadow-card: 0 14px 30px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  font-family: "Segoe UI", Tahoma, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
}

body {
  min-height: 100vh;
  background-image: radial-gradient(circle at 10% 0%, #f7faff 0%, transparent 40%),
    radial-gradient(circle at 90% 20%, #edf4ff 0%, transparent 35%);
}

.container {
  width: min(1100px, 92%);
  margin: 0 auto;
}

.site-header {
  background: linear-gradient(120deg, #0d3f68, #135486 60%, #1a659f);
  color: #fff;
  padding: 2.3rem 0;
  box-shadow: var(--shadow-soft);
  border-bottom: 1px solid rgba(255, 255, 255, 0.2);
}

.site-header h1 {
  margin: 0;
  font-size: clamp(1.6rem, 2.4vw, 2.4rem);
  letter-spacing: 0.2px;
}

.site-header p {
  margin: 0.55rem 0 0;
  color: #dceeff;
  max-width: 75ch;
}

.site-footer {
  margin-top: 2.4rem;
  padding: 1.2rem 0 1.4rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-soft);
  padding: 1.35rem;
  margin-top: 1.25rem;
}

.exercise-nav {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 0.85rem;
  margin-top: 0.95rem;
}

.exercise-nav a,
.back-link,
.button-link {
  display: inline-block;
  text-decoration: none;
  color: #fff;
  background: linear-gradient(135deg, var(--primary), #1b669f);
  padding: 0.68rem 1rem;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  font-weight: 600;
  transition: background 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
}

.exercise-nav a:hover,
.back-link:hover,
.button-link:hover {
  background: linear-gradient(135deg, var(--primary-dark), #114b7a);
  transform: translateY(-1px) scale(1.003);
  box-shadow: 0 10px 18px rgba(15, 75, 122, 0.24);
}

.back-link {
  margin-top: 0.9rem;
}

h2,
h3 {
  margin-top: 0;
}

h2 {
  font-size: clamp(1.2rem, 1.5vw, 1.55rem);
  margin-bottom: 0.65rem;
}

h3 {
  font-size: clamp(1.03rem, 1.2vw, 1.2rem);
  margin-bottom: 0.5rem;
}

p,
li {
  color: #243046;
}

code,
pre {
  font-family: "Consolas", "Courier New", monospace;
}

pre {
  background: #0f172a;
  color: #dce8ff;
  padding: 1rem;
  border-radius: 12px;
  border: 1px solid #1f2d4a;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.06);
  overflow-x: auto;
}

.table {
  width: 100%;
  border-collapse: collapse;
  overflow: hidden;
  border-radius: 10px;
}

.table th,
.table td {
  border: 1px solid var(--border);
  padding: 0.65rem;
  text-align: left;
}

.table th {
  background: #f4f8ff;
  color: #1a2f4b;
}

.table tr:nth-child(even) td {
  background: #fbfdff;
}

.demo-box {
  border: 1px dashed #b3bfce;
  padding: 1rem;
  border-radius: 12px;
  background: linear-gradient(180deg, #fcfdff, #f8fbff);
}

.note {
  padding: 0.78rem;
  border-left: 4px solid var(--accent);
  background: #eefaf8;
  border-radius: 8px;
}

/* Exercice 3 - Navigation Flexbox */
.navbar-demo {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: linear-gradient(135deg, #0f172a, #172a44);
  color: #fff;
  padding: 0.78rem 1rem;
  border-radius: 12px;
  border: 1px solid #24324b;
}

.navbar-demo .nav-links {
  list-style: none;
  display: flex;
  gap: 1rem;
  margin: 0;
  padding: 0;
}

.navbar-demo a {
  color: #dbeafe;
  text-decoration: none;
  font-weight: 500;
}

/* Exercice 3 - Cartes */
.cards {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.card {
  flex: 1 1 240px;
  display: flex;
  flex-direction: column;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem;
  box-shadow: var(--shadow-soft);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-card);
}

.card-link {
  margin-top: auto;
  align-self: flex-start;
  text-decoration: none;
  background: linear-gradient(135deg, var(--accent), #14a39a);
  color: #fff;
  padding: 0.52rem 0.86rem;
  border-radius: 7px;
  font-weight: 600;
}

/* Exercice 4 - Grid */
.grid-cards {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
}

.grid-cards .card {
  text-align: center;
  font-weight: 600;
}

.page-layout {
  display: grid;
  gap: 0.8rem;
  grid-template-areas:
    "header"
    "sidebar"
    "main"
    "footer";
}

.page-layout > * {
  border: 1px solid var(--border);
  background: #fff;
  border-radius: 10px;
  padding: 0.9rem;
}

.page-layout .header {
  grid-area: header;
}

.page-layout .sidebar {
  grid-area: sidebar;
}

.page-layout .main {
  grid-area: main;
}

.page-layout .footer {
  grid-area: footer;
}

@media (min-width: 900px) {
  .page-layout {
    grid-template-columns: 240px 1fr;
    grid-template-areas:
      "header header"
      "sidebar main"
      "footer footer";
  }
}

/* Exercice 5 - Mobile First */
.responsive-demo .container {
  width: 100%;
  padding: 15px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fff;
  box-shadow: var(--shadow-soft);
}

.responsive-demo .nav-menu {
  display: flex;
  flex-direction: column;
  gap: 5px;
}

.responsive-demo .nav-item {
  background: #f5f9ff;
  border: 1px solid var(--border);
  padding: 0.55rem;
  border-radius: 8px;
}

.responsive-demo .content {
  display: block;
  margin-top: 0.7rem;
}

.responsive-demo .main-content {
  background: #f8fbff;
  border: 1px solid var(--border);
  padding: 0.8rem;
  border-radius: 10px;
}

.responsive-demo .sidebar {
  display: none;
  background: #f2f8ff;
  border: 1px solid var(--border);
  padding: 0.8rem;
  border-radius: 10px;
}

@media (min-width: 768px) {
  .responsive-demo .nav-menu {
    flex-direction: row;
    gap: 10px;
  }

  .responsive-demo .content {
    display: grid;
    grid-template-columns: 1fr 240px;
    gap: 10px;
  }

  .responsive-demo .sidebar {
    display: block;
  }
}

@media (min-width: 1024px) {
  .responsive-demo .container {
    max-width: 980px;
    margin: 0 auto;
  }

  .responsive-demo .content {
    grid-template-columns: 2fr 1fr;
    gap: 16px;
  }
}

/* Exercice 6 - Thèmes */
.theme-preview {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
}

.theme-card {
  padding: 1rem;
  border-radius: 12px;
  box-shadow: var(--shadow-soft);
}

.theme-light {
  --bg-theme: #ffffff;
  --text-theme: #1f2937;
  --primary-theme: #2563eb;
  background: var(--bg-theme);
  color: var(--text-theme);
  border: 1px solid #dbeafe;
}

.theme-dark {
  --bg-theme: #111827;
  --text-theme: #f9fafb;
  --primary-theme: #60a5fa;
  background: var(--bg-theme);
  color: var(--text-theme);
  border: 1px solid #1f2937;
}

.theme-card a {
  color: var(--primary-theme);
  text-decoration: none;
  font-weight: 600;
}

/* Exercice 7 - Animations */
.animated-btn {
  background: linear-gradient(135deg, var(--primary), #1a659f);
  color: #fff;
  border: none;
  border-radius: 10px;
  padding: 0.8rem 1.2rem;
  font-size: 1rem;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.animated-btn:hover {
  background: linear-gradient(135deg, var(--primary-dark), #0f4c81);
  transform: translateY(-2px) scale(1.01);
  box-shadow: 0 8px 18px rgba(15, 76, 129, 0.25);
}

.spinner {
  width: 52px;
  height: 52px;
  border: 6px solid #dbeafe;
  border-top-color: #2563eb;
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

.quiz-item {
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.9rem;
  margin-bottom: 0.8rem;
  background: #fff;
  box-shadow: var(--shadow-soft);
}

.answer {
  color: #0f766e;
  font-weight: 600;
}

@media (max-width: 700px) {
  .site-header {
    padding: 1.7rem 0;
  }

  .panel {
    padding: 1rem;
  }

  .exercise-nav {
    grid-template-columns: 1fr;
  }
}