body{/*七宝(線)の背景*/
background-size:20px 20px;
background-position:10px 10px,0 0;
background-image:
radial-gradient(transparent 9px,#c80 9px,#c80 10px,transparent 10px),
radial-gradient(#fd9 9px,#c80 9px,#c80 10px,#fd9 10px);
}