* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
}

html {
  scroll-behavior: smooth;
  overflow-x: hidden;
}

body {
  min-height: 100vh;
  color: #f2f6ff;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  background: radial-gradient(ellipse at bottom, #0d1b3d 0%, #000 100%);
  position: relative;
  overflow-x: hidden;
  padding: 40px 0;
}

.stars {
  width: 2px;
  height: 2px;
  background: white;
  box-shadow: 100px 200px white, 300px 400px white, 500px 100px white,
              700px 300px white, 900px 500px white, 1300px 600px white,
              1500px 400px white, 1700px 100px white;
  animation: animStars 100s linear infinite;
  position: absolute;
  top: 0;
  left: 0;
}

@keyframes animStars {
  from { transform: translateY(0); }
  to { transform: translateY(-2000px); }
}

.container {
  z-index: 1;
  width: 90%;
  max-width: 1100px;
  text-align: center;
  padding: 40px;
  background: rgba(255, 255, 255, 0.07);
  border-radius: 20px;
  box-shadow: 0 0 30px rgba(0, 0, 255, 0.3);
  backdrop-filter: blur(10px);
  transition: all 0.5s ease;
  margin-bottom: 40px;
  overflow: hidden;
}

h1 {
  font-size: 2rem;
  color: #a5c9ff;
  margin-bottom: 15px;
}

.page-subtitle {
  color: #bcd9ff;
  font-size: 1.2rem;
  margin-bottom: 25px;
}

p {
  font-size: 1rem;
  line-height: 1.6;
  color: #e6eeff;
  margin-bottom: 30px;
}

.neon-text {
  color: #99ccff;
  text-shadow: 0 0 5px #3399ff, 0 0 10px #3399ff, 0 0 20px #3399ff, 0 0 40px #66ccff;
  animation: glow 2s ease-in-out infinite alternate;
}

@keyframes glow {
  from { text-shadow: 0 0 5px #1e90ff, 0 0 10px #1e90ff, 0 0 20px #3399ff, 0 0 40px #66ccff; }
  to { text-shadow: 0 0 10px #66ccff, 0 0 20px #99ddff, 0 0 40px #b3e0ff, 0 0 60px #cceaff; }
}

.buttons {
  display: flex;
  justify-content: center;
  gap: 15px;
  flex-wrap: wrap;
}

.btn {
  color: #fff;
  background: linear-gradient(90deg, #0033cc, #0066ff);
  padding: 12px 24px;
  border-radius: 35px;
  font-weight: 600;
  transition: all 0.3s ease;
  border: none;
  cursor: pointer;
  box-shadow: 0 0 15px rgba(0, 128, 255, 0.4);
  font-size: 0.95rem;
}

.btn:hover {
  transform: translateY(-5px) scale(1.05);
  background: linear-gradient(90deg, #004cff, #3399ff);
  box-shadow: 0 0 25px rgba(51, 153, 255, 0.6);
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 20px;
}

.card {
  background: rgba(255, 255, 255, 0.1);
  padding: 20px;
  border-radius: 15px;
  text-align: left;
  box-shadow: 0 0 15px rgba(0, 102, 255, 0.2);
  animation: fadeUp 0.8s ease both;
  transition: all 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 0 25px rgba(0, 102, 255, 0.4);
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

.card h2 {
  text-align: center;
  color: #80b3ff;
  margin-bottom: 10px;
  font-size: 1.2rem;
}

.card ul {
  list-style: none;
  padding-left: 10px;
}

.card li {
  margin: 5px 0;
}

.card a {
  color: #a3c7ff;
  text-decoration: none;
  display: inline-block;
  transition: color 0.3s ease;
}

.card a:hover {
  text-decoration: underline;
  color: #d0e3ff;
}

.back-btn {
  margin-top: 25px;
}

.section {
  display: none;
}

.active {
  display: block;
  animation: fadeIn 1s ease;
}

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

::-webkit-scrollbar {
  width: 10px;
}

::-webkit-scrollbar-track {
  background: rgba(255, 255, 255, 0.05);
  border-radius: 10px;
}

::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, #004cff, #00aaff);
  border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
  background: linear-gradient(180deg, #0077ff, #33bbff);
}

/* 💡 RESPONSIVE DESIGN */
@media (max-width: 768px) {
  body {
    padding: 20px 0;
  }

  .container {
    padding: 25px;
  }

  h1 {
    font-size: 1.6rem;
  }

  .cards {
    grid-template-columns: 1fr;
  }

  .btn {
    width: 100%;
    max-width: 250px;
  }
}
.container.section {
  width: 90%;
  margin: auto;
  margin-top: 50px;
}


#backToTop {
  position: fixed;
  bottom: 20px;
  right: 20px;
  background-color: #333;
  color: white;
  border: none;
  border-radius: 50%;
  padding: 10px 13px;
  font-size: 18px;
  cursor: pointer;
  display: none; /* cachée au départ */
  box-shadow: 0 2px 8px rgba(0,0,0,0.3);
  transition: opacity 0.3s ease;
}

#backToTop:hover {
  background-color: #555;
}