JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app>
    <div ng-controller="MainCtrl">
        <h1 ng-class="{big: isig}">{{title}}</h1>
    </div>
</div>

CSS

h1 {
    font-size: 2rem;
    color: gray;
    text-align: center;
}

.big {
    font-size: 4rem;
    color: red;
}

JavaScript

function MainCtrl($scope){
    $scope.isBig = True;
    $scope.title = "Hello World"
}