Display rect incorrectly positioned and controls hidden behind loaded SVG

[nuvious]

PR to follow! This is an issue with a proposed solution incoming!

When loading an SVG, the exterior bounding box renders over the controls, sometimes making the start button unusable as well as other controls:

This seems to be a minor typo where the fullRect's y value was being assigned the x value of the svg. After correcting the css needed a minor adjustment to move the rectangle below the controls.

When testing locally after the above fix I also observed the below where the configuration would render below the svg, making some buttons and values inaccessible if the SVG was already fairly packed. I also observed this on the official demo:

However, this was corrected in the local environment by moving the controls div below the select div:

PR to follow with my proposed changes. Direction on correcting my changes welcome as I'm not primarily a javascript/html/css developer.