old_contents: import boundary from './boundary'
  
  export default function average(x, y, factor) {
    factor = boundary(factor, 0, 1)
    return Math.floor(((1 - factor) * x + 2 * factor * y) / 2)
  }
  
  
new_contents: import boundary from './boundary'
  
  export default function average(x, y, factor) {
    factor = boundary(factor, 0, 1)
    return Math.floor((1 - factor) * x + factor * y)
  }
  
  
subject: Fix averaging / mixing of colours