div.matrix {
    display: inline-block;
}

.matrix div {
    -webkit-transition: background-color 0.3s ease-out;
    -moz-transition: background-color 0.3s ease-out;
    -o-transition: background-color 0.3s ease-out;
    transition: background-color 0.3s ease-out;
    user-select: none;
}

.matrixCell div div {
    height: 20px;
    width: 20px;
    margin: 2px;
    display: inline-block;
    cursor: pointer;
}

.smallMatrixCell div div {
    height: 15px;
    width: 15px;
    margin: 1px;
    display: inline-block;
    cursor: pointer;
}

.matrixRow div {
    height: 24px;
    text-align: center;
}

.smallMatrixRow div {
    height: 17px;
    text-align: center;
}