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

body {
    background-color: white;
}

.container {
    display: flex;
    flex-flow: row wrap;
    justify-content: space-around;
    width: 98vw;
    margin: 0px auto;
}

#header {
    flex: 1 0 100%;
    height: 15vw;
    background-color: gray;  
    margin: 8px;
    font-size: 4vw;
    color: rgb(158, 158, 158);
    align-items: center;
    display: flex;
    justify-content: center;
} 

#navbar {
    flex: 1 0 100%;
    width: 100%;
    display: flex; 
    flex-flow: row wrap;
    justify-content: space-around;
    background-color: lightgray;
    padding: 12px;
    margin: 0px 8px 8px 8px;
}

#navbar div {
    flex: 1 0 0%;
    display: block;
    border: 4px solid gray;
    background-color: white;
    margin: 10px;
    padding: 8px; 
    font-size: 1.5em;
    text-align: center;
}

#navbar div:hover {
    background-color: gray;
    cursor: pointer;
}

#navbar a {
    text-decoration: none;
    color: black;
}

#navbar div:hover > a {
    color: white;
}

#content {
    flex: 1 0 100%;
    height: 150vh;
    width: 90%;
    background-color: lightgreen; 
    display: block;
    flex-flow: row wrap;
    justify-content: space-around;
    margin-left: 20px; margin-right: 20px;
}

#footer {
    flex: 1 0 100%;
    height: 15vw;
    background-color: gray;  
    margin: 8px;
}

/* 

Responsive Layout
----------------------

*/

@media screen and (max-width: 1200px) {

    .flex {
        display: flex;
        flex-wrap: wrap;
        justify-content: center;
    }

    .container {
        width: 100%;
        margin: 0px auto;
    }

    #navbar {
        width: 100%;
        background-color: lightgray;
        flex: 1 0 100%;
    }

    #navbar div {
        flex: 1 0 0%;
        text-align: center;
    }

}