* {
    margin: 0;
    padding: 0;
    border: 0;
    box-sizing: border-box;
}

header {
    width: 100%;
    margin: auto;
}

nav {
    width: 100%;
    margin: auto;
}


body {
    background-color: green;
}

ul {
    width: 90%;
    display: flex;
    flex-direction: row;
    margin: auto;
}

li {
    list-style-type: none;
}

a {
    text-decoration: none;
    color: #FFF;
    width: 100%;
    overflow: hidden;
    background-color: blue;
    height: 40px;
    text-align: center;
    line-height: 40px;
    margin: auto;
    transition:0.3s
}

a:hover {
    background-color: pink;
    color:darkblue;
    font-weight: bold;
    font-style:italic;
    transition:0.7s;
}

.container {
    width: 90%;
    background-color: darkblue;
    margin: 20px auto;
    padding: 20px;
}

.top-box {
    display: flex;
    flex-flow: row wrap;
    margin: auto;
    width: 90%;
    background-color: purple;
}

.tall-block {
    height: 900px;
    width: 400px;
    background-color: blue;
    margin: 50px auto;
}

.solids {
    height: 900px;
    width: 60%;
    display: flex;
    flex-flow: row wrap;
    justify-content: space-between;
    margin:auto;
}

.solid-block {
    width: 40%;
    height: 40%;
    background-color: rgb(255, 255, 0);
    margin: auto;
}

.wide-block {
    width: 90%;
    height: 400px;
    background-color: aqua;
    margin: auto;
}

@media screen and (max-width:800px) {

    body {
        background-color: chartreuse;
    }

    .desktop {
        display:none;
    }

    a {
        border:2px solid white;
        width: 50%;
    }



    ul {
        border:2px solid black;
        flex-flow: row wrap;
        flex-basis:0;
    }

    .container {
        width: 90%;
        background-color: darkblue;
        margin: 20px auto;
        padding: 20px;
    }
    
    .top-box {
        display: flex;
        flex-flow: row wrap;
        margin: auto;
        width: 100%;
        background-color: purple;
    }
    
    .tall-block {
        height: 300px;
        width: 300px;
        background-color: blue;
        margin: 10px auto;
    }
    
    .solids {
        height: auto;
        width: auto;
        display: flex;
        flex-flow: column nowrap;
        margin:auto;
        gap:10px;
    }
    
    .solid-block {
        width: 300px;
        height: 300px;
        background-color: rgb(255, 255, 0);
        margin:10px auto;
    }
    
    .wide-block {
        height: 300px;
        width: 300px;
        background-color: aqua;
        margin: 10px auto;
    }
    
}