css制作三角形

#triangle-up {

width: 0;

height: 0;

border-left: 50px solid transparent;

border-right: 50px solid transparent;

border-bottom: 100px solid red;

}

#triangle-down {
    width: 0;
    height: 0;
    border-left: 50px solid transparent;
    border-right: 50px solid transparent;
    border-top: 100px solid red;
}

#triangle-left {
width: 0;
height: 0;
border-top: 50px solid transparent;
border-right: 100px solid red;
border-bottom: 50px solid transparent;
}

#triangle-right {
width: 0;
height: 0;
border-top: 50px solid transparent;
border-left: 100px solid red;
border-bottom: 50px solid transparent;
}
　　

#triangle-topleft {
width: 0;
height: 0;
border-top: 100px solid red;
border-right: 100px solid transparent;
}

#triangle-topright {
width: 0;
height: 0;
border-top: 100px solid red;
border-left: 100px solid transparent;

}

#triangle-bottomleft {
width: 0;
height: 0;
border-bottom: 100px solid red;
border-right: 100px solid transparent;
}

#triangle-bottomright {
width: 0;
height: 0;
border-bottom: 100px solid red;
border-left: 100px solid transparent;
}