body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background: #fff;
  color: #333;
}
header.banner {
  position: relative;
  background: url('images/projet8.jpg') center/cover no-repeat;
  height: 70vh;
  display: flex;
  align-items: center;
  justify-content: center;
}
header.banner .overlay {
  background: rgba(255, 69, 0, 0.6);
  color: #fff;
  padding: 20px;
  text-align: center;
}
nav ul {
  list-style: none;
  display: flex;
  justify-content: center;
  background: #e63946;
  margin: 0;
  padding: 10px 0;
}
nav ul li {
  margin: 0 15px;
}
nav ul li a {
  color: #fff;
  text-decoration: none;
  font-weight: bold;
}
.slider {
  position: relative;
  max-width: 90%;
  margin: 20px auto;
}
.slides {
  display: flex;
  overflow: hidden;
}
.slide {
  min-width: 100%;
  box-sizing: border-box;
  text-align: center;
}
.slide img {
  width: 100%;
  height: auto;
}
.prev, .next {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  background: rgba(0,0,0,0.5);
  color: white;
  border: none;
  font-size: 2rem;
  padding: 10px;
  cursor: pointer;
}
.prev { left: 10px; }
.next { right: 10px; }