JSFiddle - React, Tailwind, and code Playground

CSS

.gradient {
/*background: #f1f1f1; /* Old browsers */
background: -moz-radial-gradient(center, ellipse cover,  #ffffff 0%, #ffffff 30%, #eeeeee 100%); /* FF3.6+ */
background: -webkit-gradient(radial, center center, 0px, center center, 100%, color-stop(0%,#ffffff), color-stop(30%,#ffffff), color-stop(100%,#eeeeee)); /* Chrome,Safari4+ */
background: -webkit-radial-gradient(center, ellipse cover,  #ffffff 0%,#ffffff 30%,#eeeeee 100%); /* Chrome10+,Safari5.1+ */
background: -o-radial-gradient(center, ellipse cover,  #ffffff 0%,#ffffff 30%,#eeeeee 100%); /* Opera 12+ */
background: -ms-radial-gradient(center, ellipse cover,  #ffffff 0%,#ffffff 30%,#eeeeee 100%); /* IE10+ */
background: radial-gradient(center, ellipse cover,  #ffffff 0%,#ffffff 30%,#eeeeee 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#eeeeee',GradientType=1 );*/ /* IE6-9 fallback on horizontal gradient */
}

JavaScript

Ext.create('Ext.container.Viewport', {
    layout: 'fit',
    renderTo: document.body,
    cls: 'gradient',  // use the css class .gradient

    items: [
    {
        xtype: 'container',
        region: 'center',
        cls: 'gradient',  // use the css class .gradient

        layout: {
            type: 'vbox',
            align: 'center',
            pack: 'center'
        },
        items: [ Ext.create('Ext.Img',{ src : 'http://www.sencha.com/img/sencha-large.png' }) ]
    } ]
});