style.css

body {
    margin: 0;
    padding: 0;
    background-color: antiquewhite;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

.wrapper {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-content: center;
    align-items: center;
    height: 100vh;
    text-align: center;
}

.timer {
    width: 100%;
    margin-bottom: 10px;
    font-family: 'Orbitron', 'sans-serif';
    font-size: 10rem;
    margin-bottom: 50px;
    display: flex;
    justify-content: center;
}

.btn {
    background-color: coral;
    border: none;
    color: #fff;
    font-weight: 600;
    font-size: 30px;
    padding: 18px 60px;
    margin: 5px 15px;
    border-radius: 5px;
    cursor: pointer;
}