body            { font-family: sans-serif; background: #eee; }
a, h1, h2       { color: #377ba8; }
h1, h2          { font-family: 'Georgia', serif; margin: 0; }
h1              { border-bottom: 2px solid #eee; }
h2              { font-size: 1.2em; }

.page           { margin: 2em auto; width: 35em; border: 5px solid #ccc;
                  padding: 0.8em; background: white; }


.cell {
    width: 8px;
    height: 8px;
    background: white;
    border: 1px solid gainsboro;
}

.cell.active {background: black}
.cell:hover {
    border: 1px solid chartreuse;
    cursor: cell;
}

#world {
    border-collapse: collapse;
    border: 1px solid gainsboro;
}

.center {
    margin-left: auto;
    margin-right: auto;
}