lib/Runner.js
function interpolate(min, max, ratio) {
  return Math.floor(ratio * ((max + 0.5) - min) + min);
}
function interpolate(min, max, ratio) {
  return Math.floor(ratio * ((max + 0.5) - min) + min);
}
Given float `ratio` in [0, 1], return integer value in [min, max]. interpolate(min, max, 0.0) === min interpolate(min, max, 1.0) === max