:root {
    --primary-color: #000;
    --secondary-color: #000;
    --font-family: 'Roboto', sans-serif;
}

body {
    font-family: var(--font-family);
    margin: 0;
    padding: 0;
    line-height: 1.6;
    color: var(--secondary-color);
    background-color: #fff; /* Nền sáng */
}

h1, h2, h3 {
    color: var(--primary-color);
}

/* Extra small devices (phones, <576px) */
@media (max-width: 575.98px) {
    body {
        font-size: 14px;
    }
}

/* Small devices (landscape phones, 576px and up) */
@media (min-width: 576px) and (max-width: 767.98px) {
    body {
        font-size: 16px;
    }
}

/* Medium devices (tablets, 768px and up) */
@media (min-width: 768px) and (max-width: 991.98px) {
    body {
        font-size: 18px;
    }
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) and (max-width: 1199.98px) {
    body {
        font-size: 20px;
    }
}

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
    body {
        font-size: 22px;
    }
}