body{
  background: #008b8b;
  color: #eee;
  font-family: sans-serif;
  text-align: center;
}

#tablero{
  background: url(http://i0.kym-cdn.com/photos/images/original/001/303/313/2e6.jpg);
  box-shadow: 0 10px 10px -6px rgba(0, 0, 0,);
  border-radius: 3px;
  border-collapse: collapse;
  width: 400px;
  height: 400px;
  margin: auto;
}

#tablero td{
  color: #222;
  font-size: 36px;
  text-shadow: 1px 1px 1px rgba(255, 255, 255);
  width: 50px;
  height: 50px;
}

#tablero tr:nth-child(odd) td:nth-child(even),
#tablero tr:nth-child(even) td:nth-child(odd){
  background: rgb(0, 0, 0);
}

#tablero tr:nth-child(n+7) td{
  color: #fff;
  text-shadow: 1px 1px 1px rgba(0,0,0);
}


#tablero tr:nth-child(odd) td:nth-child(even):hover, #tablero tr:nth-child(even) td:nth-child(odd):hover{
background: gray;

}

#tablero tr:nth-child(odd) td:nth-child(odd):hover, #tablero tr:nth-child(even) td:nth-child(even):hover{
background: skyblue;

}