JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <button>O</button><button>O</button>
</div>

CSS

.container {
    width: 100%;
    background-color: rgb(120, 200, 200);
    text-align: center;
}
button {
    border: 0;
    width: 3rem;
    height: 3rem;
    opacity: 0.8;
    background-color: gray;
}