body {
   margin: 0;
   font-family: Arial, Helvetica, sans-serif;
  }
  
  #menu_avancee {
	margin-top: 10px;
	transition: all 0.3s ease;
	}

  .lang-warning {
  margin-top: 8px;
  background-color: #fff3cd;
  padding: 10px;
  border-left: 5px solid #ffc107;
  color: #856404;
  border-radius: 6px;
  font-size: 0.95em;
  }

  #lang-message:empty {
    display: none;
  }

  .topnav {
   overflow: hidden;
   background-color: #333;
  }

  .topnav a {
   float: left;
   display: block;
   color: #f2f2f2;
   text-align: center;
   padding: 14px 16px;
   text-decoration: none;
   font-size: 17px;
   border-radius: 10px 10px 10px 10px;
  }

  .topnav a:hover {
   background-color: #ddd;
   color: black;
  }

  .topnav a {
   background-color: #04AA6D;
   color: white;
  }

  .topnav .icon {
   display: none;
  }

/*début recherche dans blog*/
.topnav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
}

.topnav-search-form {
  display: flex;
  align-items: center;
  margin-left: auto;
  margin-right: 10px;
}

.topnav-search-form input[type="text"] {
  padding: 7px;
  border: 1px solid #ccc;
  border-radius: 3px 0 0 3px;
  outline: none;
  width: 200px;
  margin-top: 13px;
  margin-right: 0px;
  border-radius: 10px 0px 0px 10px;
}

.topnav-search-form button {
  padding: 5px 8px;
  border: 1px solid #ccc;
  background-color: #eee;
  border-left: none;
  border-radius: 0 10px 10px 0;
  cursor: pointer;
}
/*fin recherche dans blog*/

  @media screen and (max-width: 600px) {
   .topnav a:not(:first-child) {
    display: none;
   }

   .topnav a.icon {
    float: right;
    display: block;
   }
  }

  @media screen and (max-width: 600px) {
   .topnav.responsive {
    position: relative;
   }

   .topnav.responsive .icon {
    position: absolute;
    right: 0;
    top: 0;
   }

   .topnav.responsive a {
    float: none;
    display: block;
    text-align: left;
   }
  }
  

.nav-search form {
  display: flex;
  height: 40px;
}

.nav-search input {
  flex: 1;
  padding: 0 15px;
  border: 2px solid #ddd;
  border-right: none;
  border-radius: 20px 0 0 20px;
  height: 100%;
  box-sizing: border-box;
}

.nav-search button {
  width: 50px;
  background: #4361ee;
  color: white;
  border: 2px solid #4361ee;
  border-radius: 0 20px 20px 0;
  cursor: pointer;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
}

.nav-search button i {
  font-size: 16px;
  line-height: 1;
}

/*	-----------------------	*/

<!-- CSS corrigé -->
/* Menu desktop visible par défaut */
.nav-menu {
  display: flex;
  align-items: center;
  gap: 20px;
}

/* Bouton menu mobile caché par défaut */
.menu-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 10px;
  z-index: 1001;
}

.hamburger {
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 30px;
}

.hamburger span {
  display: block;
  width: 100%;
  height: 3px;
  background: #333;
  border-radius: 2px;
  transition: all 0.3s ease;
}

/* Menu mobile caché par défaut */
.mobile-menu {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.95);
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
}

.mobile-menu.active {
  display: block;
  opacity: 1;
  visibility: visible;
}

.mobile-menu-content {
  position: absolute;
  top: 80px;
  left: 0;
  right: 0;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 15px;
}

.mobile-menu-content a {
  color: white;
  text-decoration: none;
  font-size: 1.2rem;
  padding: 15px;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

/* États du bouton hamburger */
.menu-toggle.active .hamburger span:nth-child(1) {
  transform: rotate(45deg) translate(6px, 6px);
}

.menu-toggle.active .hamburger span:nth-child(2) {
  opacity: 0;
}

.menu-toggle.active .hamburger span:nth-child(3) {
  transform: rotate(-45deg) translate(6px, -6px);
}

/* Responsive */
@media (max-width: 768px) {
  .nav-menu {
    display: none; /* Cache le menu desktop */
  }
  
  .menu-toggle {
    display: block; /* Affiche le bouton hamburger */
  }
}