#nw {
  width: 30px;
  height: 30px;
  background-image: url('4/nw.png');
  background-repeat: no-repeat;
}
#nn {
  background-image: url('4/nn.png');
  background-repeat: repeat-x;
}
#ne {
  width: 30px;
  height: 30px;
  background-image: url('4/ne.png');
  background-repeat: no-repeat;
}
#ww {
  background-image: url('4/ww.png');
  background-repeat: repeat-y;
}
#ee {
  background-image: url('4/ee.png');
  background-repeat: repeat-y;
}
#sw {
  width: 30px;
  height: 30px;
  background-image: url('4/sw.png');
  background-repeat: no-repeat;
}
#ss {
  background-image: url('4/ss.png');
  background-repeat: repeat-x;
}
#se {
  width: 30px;
  height: 30px;
  background-image: url('4/se.png');
  background-repeat: no-repeat;
}