JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://openlayers.org/dev/OpenLayers.js"></script>
<div id="map"></div>

CSS

#map{
	border: 6px solid #7AC49F;
    border-radius: 30px 30px 30px 30px;
    bottom: 0;
    display: block;
    height: auto;
    left: 0;
    margin: 39px 10px 10px;
    position: absolute;
    right: 0;
    top: 0;
	background-color:#eee;
}

div.olMapViewport {
    border-radius: 25px;
     display: block;
}

.olLayerDiv{
   border-radius: 25px; 
     display: block;
}
}

JavaScript

var map = new OpenLayers.Map( 'map', {theme:null,
                    controls:[new OpenLayers.Control.Navigation()]} );
            layer = new OpenLayers.Layer.WMS( "OpenLayers WMS",
                    "http://vmap0.tiles.osgeo.org/wms/vmap0",
                    {layers: 'basic'} );
            map.addLayer(layer);
            map.setCenter([3, 49], 5);

var startPt=new OpenLayers.Geometry.Point( 5, 45);
var endPt=new OpenLayers.Geometry.Point(7,55);

//make the line:
var line=new OpenLayers.Geometry.LineString([startPt, endPt]);

//style
var style={strokeColor:"#fffff", strokeWidth:3};
//make vector 
var fea=new OpenLayers.Feature.Vector(line, {}, style);

//make vectorLayer
var vec= new OpenLayers.Layer.Vector();

//add the feature
vec.addFeatures([fea]);

//add to map
map.addLayer(vec);