/**
 * Just a snippet, but it should work
 */
const {
  roundedHeight,
  height,
  width
} = this.props;

const heightSq = Math.pow(roundedHeight - height, 2);
const widthSq  = Math.pow(width / 2, 2);
const xSq      = Math.pow(x, 2);
/**
 * This will give `y` where 0 = same level as `height`. Maximum
 * value is `roundedHeight`.
 */
let y = Math.round(Math.sqrt(heightSq * (1 - xSq/widthSq)));