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

body {
    font-family: Arial, sans-serif;
}

.container {
    width: 95%;
    margin: auto;
}

h2 {
    text-align: center;
    margin: 10px 0;
}

/* ROW */
.row {
    display: flex;
    gap: 5px;
    margin-bottom: 5px;
}

/* COLUMN */
.col {
    display: flex;
    flex-direction: column;
    gap: 5px;
}

/* LEFT 70% */
.main {
    flex: 7;
}

/* RIGHT 30% */
.sidebar {
    flex: 3;
}

/* BOX */
.box {
    background: #3aa4c4;
    color: white;
    padding: 15px;
    text-align: center;
}

/* chiều cao khác nhau */
.tall {
    height: 150px;
}

.small {
    height: 50px;
}

/* image */
.image-box img {
    width: 100%;
    max-width: 200px;
}

/* RESPONSIVE */
@media (max-width: 768px) {
    .row {
        flex-direction: column;
    }
}