body { margin:0; font-family:Arial; }
.header { display:flex; justify-content:space-between; align-items:center; padding:15px; background:#f5f5f5; }
.menu a { margin-left:20px; text-decoration:none; color:#333; }
.mobile-btn { display:none; font-size:28px; background:none; border:none; }
.mobile-menu { display:flex; flex-direction:column; background:#fff; padding:10px; border-bottom:1px solid #ccc; }
.hidden { display:none; }
.hero { padding:60px; text-align:center; background:#e8ffe8; }
@media (max-width:768px){
  .desktop { display:none; }
  .mobile-btn { display:block; }
}