JSFiddle - React, Tailwind, and code Playground

HTML

<body>
        <!--Button-->
        <div class="center marginB">
            <a id="startChat" class="btn">Button</a> 
        </div>  

        <!--Cursor-->
        <div class="cursor"></div>
</body>

CSS

.marginB:hover ~ .cursor { background-color: yellow; }
 
 .cursor {
        width: 10px;
        height: 10px;
        border-radius: 50%;
        position: absolute;
        background-color: black;
    }

    .btn {
        text-decoration: none;
        font-family: sans-serif;
        font-weight: bold;
        text-transform: uppercase;
        color: black;
        background-color: white;
        border: 4px solid black;
        padding: 0.5rem 0.8rem;
        display: inline-block;
        margin: 100px 100px;
    }