I'm using cesium map 3D i want to reduce its size but it is not getting reduced

<style type="text/css">
html, body, #cesiumContainer {
    width: 100%; height: 60%; margin: 0; padding: 0; overflow: hidden;
    font-family: sans-serif;
}
</style>

I'm trying to give height 60% but this is not working.

Sandcastle link Any suggestions Please, Thanks