code: function randnBM() {
    const u = 1 - Math.random() // Subtraction to flip [0, 1) to (0, 1].
    const v = 1 - Math.random()
    return Math.sqrt(-2.0 * Math.log(u)) * Math.cos(2.0 * Math.PI * v)
  }
docs: Standard Normal constiate using Box-Muller transform. http://stackoverflow.com/a/36481059