JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
    <div id="number"></div>
    <div class="buttons">
        <button type="button" id="start" onclick="start(this);">Старт</button>
        <button type="button" id="random" class="hide" onclick="rand();">Ещё</button>
        <button type="button" id="share" class="hide">Поделиться</button>
    </div>
</div>

CSS

.box {
    height: 500px;
    position: relative;
    background-image: url(http://eandys.ru/image.php?di=PZUV);
}
.buttons {
    position: absolute;
    left: 0;
    bottom: 0;
    width: 100%;
}
.buttons > button {
    width: 156px;
    height: 39px;
    display: block;
    margin: 3px auto;
}
#number {
    text-align: center;
    color: #000;
    text-shadow: 0 0 3px #fff;
    font-size: 70px;
    padding: 180px;
}
.hide {
    display: none !important;
}

JavaScript

function rand(){
	document.getElementById('number').innerHTML = Math.ceil(Math.random()*1000);
}

function start(el){
    var nodeList = document.querySelectorAll('.hide')
    for (var i = 0; i < nodeList.length; ++i) {
      nodeList[i].className = '';
    }
    el.className = 'hide';
    rand();
}