body{
    margin: 100px;
}
.box {
    background-color: yellow;
    margin: auto;
    width: 1400px;
    border: 1px solid black;
}
.red {
    background-color: red;
}
.green {
    background-color: green;
}
.blue {
    background-color: blue;
}
.red, .green, .blue {
    float: left;    
    width: 100px;
    height: 100px;
    margin: 15px;
    border: 5px solid black;
    text-align: center;
    font-size: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
}
footer {
    text-align: center;
    background-color: darkgray;
    clear: both;
    font-size: 20px;
    padding: 10px;
    border-top: 1px solid black;
}
.name {
    font-weight: bold;
    font-size: 40px;
}
h1 {
    text-align: center;
    font-size: 60px;
}
@media (max-width: 1400px) {
    .box {
        width: 840px;
    }
    body {
        background-color: gray;
    }
}
@media (max-width: 840px) {
    .box {
        width: 560px;
    }
    body {
        background-color: lightblue;
    }
}
@media (max-width: 560px) {
    .box {
        width: 140px;
    }
    body {
        background-color: orange;
    }
    h1 {
        font-size: 18px;
    }
    .name{
        font-size: 16px;
    }
}