/* 等腰三角形(箭头朝上); */
#div1{
width: 0; height: 0; border-bottom: 100px solid cyan; border-left: 50px solid transparent; border-right: 50px solid transparent; }
/* 等腰三角形(箭头朝下); */
#div2{
width: 0; height: 0; border-top: 100px solid cyan; border-left: 50px solid transparent; border-right: 50px solid transparent; }
/* 等腰三角形(箭头朝左); */
#div3{
width: 0; height: 0; border-right: 100px solid cyan; border-top: 50px solid transparent; border-bottom: 50px solid transparent; }
/* 等腰三角形(箭头朝右); */
#div4{
width: 0; height: 0; border-left: 100px solid cyan; border-top: 50px solid transparent; border-bottom: 50px solid transparent; }
/* 直角三角形(箭头左上); */
#div5{
width: 0; height: 0; border: 50px solid gray; border-right: 50px solid transparent; border-bottom: 50px solid transparent; }
/* 直角三角形(箭头右下); */
#div6{
width: 0; height: 0; border: 50px solid lightblue; border-left: 50px solid transparent; border-top: 50px solid transparent; }