body {
    margin: 0;
    font-family: Arial;
}

/* khung trang */
.container {
    width: 100%;
}

/* header */
header {
    background: #FCC;
    text-align: center;
    padding: 20px;
}

/* 3 cột */
.box {
    width: 33.33%;
    float: left;
    padding: 15px;
    box-sizing: border-box;
}

.box h3 {
    margin-top: 0;
}

/* hình */
.box img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

/* footer */
footer {
    clear: both;
    background: #FCC;
    text-align: center;
    padding: 15px;
}