JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="nav">
    <li>
        <input type="button" id="start" />
    </li>
    <li>
        <input type="button" id="start" />
    </li>
    <li>
        <input type="button" id="start" />
    </li>
    <li>
        <input type="button" id="start" />
    </li>
</ul>

CSS

input {
background:url(ic_action_back.png);
background-color: white;
background-repeat: no-repeat;
background-size: contain;
background-position:center; 
width: 100%;
height: 100%;
padding: 0;
margin: 0;
}

#nav {
    margin: 0;
    padding: 0;
    display: table;
    width: 100%;
}

#nav li {
    background-color: red;
    display: table-cell;
    padding: 0;
    width: 25%;  /* (100 / numItems)% */
    text-align: center;
    border-right: 1px solid #fff;
    white-space: nowrap;
    vertical-align: top;
}