JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tri"></div>
<div class="rot bigTri"></div>
<div class="rot tri"></div>

CSS

/* based on http://www.cagintranet.com/archive/create-an-ipad-like-dropdown-popover/ */
.tri {
    width: 0px;
    border-top: 16px solid rgba(0,0,0,0);
    border-left: 16px solid rgba(0,0,0,0);
    border-right: 16px solid rgba(0,0,0,0);
    border-bottom: 16px solid black;
}

.bigTri {
    top: 100px;
    width: 0px;
    border-top: 64px solid rgba(0,0,0,0);
    border-left: 64px solid rgba(0,0,0,0);
    border-right: 64px solid green;
    border-bottom: 64px solid rgba(0,0,0,0);
}

.rot {
    -webkit-transform: rotate(-30deg);
    -moz-transform: rotate(-30deg);
    transform: rotate(-30deg);
}