style.css

@import url('https://fonts.googleapis.com/css?family=Roboto;wght@400;700&display=swap');

* {
    box-sizing: border-box;
}

body {
    background-color: #efedd6;
    font-family: 'Roboto', sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    margin: 0;
}

h1 {
    margin: 10px;
}

.box {
    background-color: steelblue;
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 400px;
    height: 200px;
    margin: 10px;
    border-radius: 10px;
    box-shadow: 2px 4px 5px rgba(0, 0, 0, 0.3);
    /* move the boxes off the screen along the X axis */
    transform: translateX(400%);
    transition: transform 0.7s ease;
}

/* every other content box is moved off the screen but to the 
opposite side */
.box:nth-of-type(even) {
    transform: translateX(-400%);
}

/* boxes with class of show are shown in the middle of X axis */
.box.show {
    transform: translateX(0);
}

.box h2 {
    font-size: 45px;
}