正三角形
【css】
body{/*正三角形を敷き詰めた背景*/
background-color:pink;
background-size:52px 90px;
background-position:0 0,0 0,26px 45px,26px 45px
background-image:
linear-gradient(-60deg,rgba(255,255,255,0.5) 25%, transparent 0),
linear-gradient(60deg,rgba(255,255,255,0.5) 25%, transparent 0),
linear-gradient(-60deg,rgba(255,255,255,0.5) 25%, transparent 0),
linear-gradient(60deg,rgba(255,255,255,0.5) 25%, transparent 0);
}
適宜必要なプロパティを追加してください