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

body {
        background-color: grey;
        color: black;
}

h1 {
    position: absolute; top: 160px; right: 16px;
    font-size: 14pt;
    font-weight: normal;
    color: orange;
    font-family: Georgia, 'Times New Roman', Times, serif;
}

main {
    position: absolute;
    top: 50%;
    width: 100%;
    transform: translateY(-50%);
    display: flex;
    flex-flow: row wrap;
    justify-content: space-evenly;
}

/* child selector */
main > div {
    background-color: blue;
    flex: 0 0 30%;
    aspect-ratio: 1;
}

#feature {
    position: relative;
    background-color: transparent;
}

#feature > div {
    background-color: blanchedalmond;
    width: 45%;
    height: 45%;
    position: absolute;
}

#feature > div:nth-child(1) {
    top: 0; left: 0;
}

#feature > div:nth-child(2) {
    top: 0; right: 0;
}

#feature > div:nth-child(3) {
    bottom: 0; left: 0;
}

#feature > div:nth-child(4) {
    bottom: 0; right: 0;
}

nav {
    display: flex;
    flex-flow: row wrap;
    justify-content: space-evenly;
    padding-top: 8px;
    gap: 12px;
    margin-left: 8px;
    margin-right: 8px;
}

nav > a {
    background-color: blue;
    padding: 12px 16px;
    flex: 1 0 auto;
    text-align: center;
    color: orange;
    text-decoration: none;
}

@media screen and (max-width: 750px) {
    
    nav > a {
        flex: 0 0 40%;
    }

    main > div {
        main {
            position: static;;
            transform: translateY(0%);
            padding-top: 40px;
        }
        
        /* child selector */
        main > div {
            flex: 0 0 96%;
            margin-bottom: 40px;
        }
        
        #feature {
            position: relative;
            background-color: transparent;
        }
        
        #feature > div {
            background-color: blanchedalmond;
            width: 45%;
            height: 45%;
            position: absolute;
        }
        
        #feature > div:nth-child(1) {
            top: 0; left: 0;
        }
        
        #feature > div:nth-child(2) {
            top: 0; right: 0;
        }
        
        #feature > div:nth-child(3) {
            bottom: 0; left: 0;
        }
        
        #feature > div:nth-child(4) {
            bottom: 0; right: 0;
        }
    }
}