triangle css

    #circle {
      width: 100px;
      height: 100px;
      background: red;
      border-radius: 50%
    }
  

#triangle {
    width: 0;
    height: 0;
    border-left: 18px solid transparent;
    border-right: 18px solid transparent;
    border-bottom: 30px solid blue;
}

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

/*corner triangles if you want normal triangles look at other answers*/
    #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-topright {
      width: 0;
      height: 0;
      border-top: 100px solid red;
      border-left: 100px solid transparent;
    }