* {
    margin: 5px;
    border-radius: 5px;
}

body {
    display: flex;
    flex-wrap: wrap;
    align-items: flex-start;
    width: 100%;
    justify-content: space-around;
}

header {
    background-color: #995be3;
    width: 100%;
    text-align: left;
}

h1,
h2,
h3,
h4 {
    width: 100%;
    color: #fff;
    text-align:center;
}

nav {
    background-color: #ffe54f;
    width: 100%;
}

nav select {
    display: inline;
    background-color: rgb(30, 0, 255);
}

nav ul {
    display: none;
}

nav ul li {
    list-style: none;
}



aside {
    width: 100%;
    background-color: #cba8f4;
    width: 25%;  
}


main {  
    background-color: #fff;  
    color: #333;  
    width: 75%;  
} 


footer {
    background-color: #995be3;
    width: 100%;
    text-align:center;
}


#contingut_principal iframe {
    width: 800px;
    height: 600px;
}


/* Versió de tablet o desktop */
@media screen and (min-width: 936px) {

    nav {
        width: 100%;
        height: 40px;
    }

    nav select {
        display: none;
    }

    nav ul,
    nav ul li {
        display: inline;
    }

    main {
        width: 70%;
    }

}