*{
    box-sizing: border-box;
}
.container{
    margin: 0px auto;
    width: 100%;
}
header {
    background-color:yellow;
    padding-top: 2em;
    text-align: center;
    height: 200px;
}
main{
    display: flex;
    flex-wrap: wrap;
}
.red{
    width: 100%;
    height: 200px;
    background-color: red;
}

.blue{
    width: 100%;
    height: 200px;
    background-color:blue;
}


.green{
    width: 100%;
    height: 200px;
    background-color: green;
}

.yellow{
    width: 100%;
    height: 200px;
    background-color: yellow;
}

.brown{
    width: 100%;
    height: 200px;
    background-color: brown;
}
.orange{
    width: 100%;
    height: 200px;
    background-color: orange;
}

.pink{
    width: 100%;
    height: 200px;
    background-color: pink;
}

.gray{
    width: 100%;
    height: 200px;
    background-color: gray;
}

.black{
    width: 100%;
    height: 200px;
    background-color: black;
}


@media screen and (min-width: 500px) and (max-width: 999px) {
    main{
        display: flex;
        flex-wrap: wrap;
    }
    .red, .blue, .yellow, .pink, .black, .gray, .orange, .brown{
        width: 100%;
    }
    .green{
        width: 100%;
    }
}

@media screen and (min-width: 1000px) and (max-width: 1999px) {
    main{
        display: flex;
        flex-wrap: wrap;
    }
    .red, .blue, .yellow, .pink, .black, .gray, .orange, .brown{
        width: 50%;
    }
    .green{
        display: none;
    }
}


@media screen and (min-width: 2000px){
    main{
        display: flex;
        flex-wrap: wrap;
    }
    .red, .blue, .yellow, .pink, .gray, .brown{
        width: 33%;
    }
    .green, .orange, .black{
        width: 34%;
    }
}

@media screen and (orientation:landscape){
    header{
        background-color: orange;
        color: green;
    }
}