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

body {
    font-family: 'Times New Roman', Times, serif;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background-color: #ffffff;
}

header, footer {
    padding: 20px;
    text-align: center;
    color: black;
}

main {
    flex: 1;
    padding: 20px;
    display: grid;
    gap: 20px;
}


.box {
    width: 100%;
    height: 220px;
    background-color: #ddd;
    overflow: hidden;
}

.box img,
.box iframe {
    width: 100%;
    height: 100%;
    object-fit: cover;
}



@media (max-width: 600px) {

    main {
        grid-template-columns: 1fr;
    }

}



@media (min-width: 601px) and (max-width: 900px) {

    main {
        grid-template-columns: 1fr 1fr;
    }

    .box:nth-child(1) {grid-column:1;}
    .box:nth-child(2) {grid-column:2;}
    .box:nth-child(3) {grid-column:1;}
    .box:nth-child(4) {grid-column:2;}
    .box:nth-child(5) {grid-column:1;}
    .box:nth-child(6) {grid-column:2;}

}



@media (min-width: 901px) {

    main {
        grid-template-columns: repeat(3, 1fr);
    }

    /* slike gore */
    .box:nth-child(1) {grid-column:1;}
    .box:nth-child(2) {grid-column:2;}
    .box:nth-child(3) {grid-column:3;}

    /* videa dolje */
    .box:nth-child(4) {grid-column:1;}
    .box:nth-child(5) {grid-column:2;}
    .box:nth-child(6) {grid-column:3;}

}