Css triangle

                    
.arrow-up {
    width: 0;
    height: 0;
    border-left: 10px solid transparent;
    border-right: 10px solid transparent;
    border-bottom: 10px solid black;
}

.arrow-down {
    width: 0;
    height: 0;
    border-left: 20px solid transparent;
    border-right: 20px solid transparent;
    border-top: 20px solid red;
}

.arrow-left {
    width: 0;
    height: 0;
    border-top: 15px solid transparent;
    border-bottom: 15px solid transparent;
    border-right: 15px solid blue;
}

.arrow-right {
    width: 0;
    height: 0;
    border-top: 30px solid transparent;
    border-bottom: 30px solid transparent;
    border-left: 30px solid green;
}