html, body {
    margin: 0 auto;
    font-family: sans-serif;
}
.container {
    margin: 0 auto;
    max-width: 960px;
}
canvas {
    margin: 0 auto;
    display: block;
    border: 2px solid #333;
}

input {
    padding: 4px;
    width: 50px;
}
.details {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
}

.flex {
    flex: 1 0 auto;
    text-align: center;
}

#new-game {
    padding: 10px;
}