css.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

body {
    background: gray;
}

.container {
    background: #fff;
    margin: auto;
    margin-top: 100px;
    border: 1px solid black;
    width: 600px;
    justify-content: space-around;
    padding: 0 20px;
    border-radius: 5px;
}

.container span {
    font-size: 100px;
}

.container .clock {
    display: flex;
}

.container .num {
    text-align: center;
    padding: 0 10px;
}

.container .btn-control{
    display: flex;
    justify-content: space-between;
}


button {
    font-size: 25px;
    height: 50px;
    width: 50px;
}

.container .action {
    padding: 20px;
}

.action button{
    width: 100px;
}