:root {
    --primary-color: #f05123;
    --black-color: #000;
    --white-color: #fff;
    --gray-color: #666;
    --text-color: #333;
    --plum-color: #b80257;
    --fb-color: #4080ff;
    --mail-color: #f47425;
    --first-color: #1dbfaf;
    --second-color: #1dbfaf;
    --button-color: #1dbfaf;
}

* {
    box-sizing: inherit;
}

html {
    /* Thiếu box-sizing : border-box là nó vỡ cmn kích thước.  */
    font-size: 62.5%;
    line-height: 1.6rem;
    font-family: 'Open Sans', sans-serif;
    box-sizing: border-box;
}


/* ==============animation */

@keyframes dropDown {
    from {
        transform: scaleY(0);
    }
    to {
        transform: scaleY(1);
    }
}

@keyframes toRight {
    from {
        padding-left: 25px;
    }
    to {
        padding-left: 29px;
    }
}

@keyframes scaleImg {
    from {
        opacity: 1;
        transform: scale(1);
    }
    to {
        opacity: 0.7;
        transform: scale(1.05);
    }
}

@keyframes changeColor {
    from {
        color: hsla(0, 0%, 100%, .7);
    }
    to {
        color: var(--plum-color);
    }
}


/* Chuẩn bị nền móng responsive */

.grid {
    width: 100%;
    max-width: 1224px;
    margin: 0 auto;
}

.grid__full-width {
    width: 100%;
}

.grid__row {
    display: flex;
    flex-wrap: wrap;
    margin-left: -12px;
    margin-right: -12px;
}

.grid__col-4 {
    padding-left: 12px;
    padding-right: 12px;
    width: 33.33333%;
}

.grid__col-6 {
    padding-left: 12px;
    padding-right: 12px;
    width: 50%;
}

.grid__col-3 {
    padding-left: 12px;
    padding-right: 12px;
    width: 25%;
}

.grid__col-2 {
    padding-left: 12px;
    padding-right: 12px;
    width: 16.66667%;
}

.btn {
    display: block;
    min-width: 180px;
    min-height: 42px;
    line-height: 42px;
    padding: 0 25px;
    text-decoration: none;
    border: none;
    outline: none;
    border-radius: 20px;
    color: var(--white-color);
    background-color: var(--primary-color);
    text-transform: uppercase;
    box-shadow: 0 0 1px transparent;
    font-size: 1.6rem;
    font-weight: 500;
    cursor: pointer;
}

.btn--size-s {
    border-radius: 20px;
    text-decoration: none;
    border: none;
    outline: none;
    display: block;
    width: 72px;
    height: 29px;
    line-height: 29px;
    text-align: center;
    color: var(--white-color);
    background-color: var(--primary-color);
    box-shadow: 0 0 1px transparent;
    cursor: pointer;
    font-weight: 400;
    font-size: 1.4rem;
}