/* quitar estilos por defecto */
*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body{
    font-family: Arial;
}

/* menu principal */
.menu ul{
    list-style: none;
    background: #333;
    display: flex;
}

.menu ul li{
    position: relative;
}

.menu ul li a{
    display: block;
    padding: 15px 20px;
    color: white;
    text-decoration: none;
}

/* hover */
.menu ul li a:hover{
    background: #555;
}

/* submenu */
.submenu{
    position: absolute;
    background: #444;
    top:100%;
    left:0;
    flex-direction: column;
    min-width: 150px;

    opacity: 0;
    visibility: hidden;
    transition: 0.3s;
}

/* items submenu */
.submenu li a{
    padding: 12px;
}

/* mostrar submenu */
.dropdown:hover .submenu{
    opacity: 1;
    visibility: visible;
}