*, ::before, ::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: Arial, Helvetica, sans-serif;
    background: linear-gradient(to right, #283048, #859398); /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */
    color: #f1f1f1;
}

h1, h2 {

    text-align: center;
    font-size: 50px;
    margin: 50px auto 0;

}

.container {

    display: grid;
    grid-template: repeat(3,100px) / repeat(3,100px);
    width: 300px;
    height: 300px;
    margin: 50px auto;

}

.cell {

    width: 100px;
    height: 100px;
    color: #f1f1f1;
    border: 1px solid #f1f1f1;
    cursor: pointer;
    font-size: 60px;
    display: flex;
    justify-content: center;
    align-items: center;
    
}