.triangle {
position: absolute;
width: 0;
height: 0;
top: 11rem;
left: 4.1rem;
border-bottom-right-radius: 8px;
border-left: 9rem solid transparent;
border-top: 1.65rem solid transparent;
border-bottom: 4rem solid rgba(7, 67, 36, 0.8);
border-right: 3.55rem solid rgba(7, 67, 36, 0.8);
}
效果如下图: