Draw Rectangle using OpenLayers 4?

I just want to draw rectangle for style. if I do this

 image: new ol.style.RegularShape({
        fill: fill,
        //stroke: stroke,
        // offsetY: -25,
        points: 4,
        radius1: 30,
        //radius2:20,
        angle: Math.PI / 4
    })

it gives me this square

else if i do this

 image: new ol.style.RegularShape({
        fill: fill,
        //stroke: stroke,
        // offsetY: -25,
        points: 4,
        radius1: 30,

        radius2:10,
        angle: Math.PI / 4
    })

it gives me this

How can I draw a rectangle?