body{/*オーバーチェック*/
background-color:#fff;
background-size:42px 42px;
background-image:
linear-gradient(90deg,transparent 10px,#fea 10px,#fea 11px,transparent 11px,transparent 31px,#fea 31px,#fea 32px,transparent 32px),
linear-gradient(180deg,transparent 10px,#fea 10px,#fea 11px,transparent 11px,transparent 21px,rgba(255,50,100,.2) 21px,rgba(255,50,100,.2) 31px,#fea 31px,#fea 32px,rgba(255,50,100,.2) 32px),
linear-gradient(90deg,transparent 21px,rgba(255,50,100,.2) 21px);
}