style.css

.container {
    width: 56%;
    margin: 0 auto;
    background-color: #283747;
    display: -ms-flexbox;
    /* IE10 */
    -ms-flex-wrap: wrap;
    /* IE10 */
    flex-wrap: wrap;
    padding: 0 4px;
    display: grid;
    grid-template-columns: auto 445px;
    font-family: 'Roboto', sans-serif;
}

.grid {
    display: flex;
    flex-wrap: wrap;
    width: 440px;
    height: 440px;
    margin: 0 auto;
}

.grid div {
    width: 100px;
    height: 100px;
    background-color: #DE354C;
    font-size: 40px;
    text-align: center;
    color: #f3f3f3;
    font-weight: bold;
    margin-right: 5px;
    margin-left: 5px;
}

.column-container {
    padding: 0 4px;
}

.game-over {
    color: white;
    position: absolute;
    text-align: center;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    padding: 20px;
    background-color: teal;
    min-width: 200px;
    display: grid;
}

.game-over-message {
    padding: 10px;
}

.heading {
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: #DE354C;
    font-size: 26px;
}

.grid-above-game {
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: #DE354C;
}

.score-container, .best-container {
    min-width: 40px;
    position: relative;
    display: block;
    background: #932432;
    padding: 15px 25px;
    font-size: 20px;
    font-weight: bold;
    color: white;
    text-align: center;
}

.scores-container {
    float: right;
    display: flex;
    margin: 10px;
}

.scores-container *+* {
    margin-left: 5px;
}

.new-game-button {
    background: #DE354C;
    padding: 0 25px;
    color: #f9f6f2;
    height: 40px;
    line-height: 42px;
    cursor: pointer;
    display: block;
    text-align: center;
    flex-shrink: 0;
}

.rules-container {
    margin-top: 10px;
    padding-top: 20px;
    color: #f9f6f2;
    text-align: justify;
    text-justify: inter-word;
}