code: func DrawRect(dst *ebiten.Image, x, y, width, height float64, clr color.Color) {
  	ew, eh := emptyImage.Size()
  
  	op := &ebiten.DrawImageOptions{}
  	op.GeoM.Scale(width/float64(ew), height/float64(eh))
  	op.GeoM.Translate(x, y)
  	op.ColorM.Scale(colorScale(clr))
  	// Filter must be 'nearest' filter (default).
  	// Linear filtering would make edges blurred.
  	_ = dst.DrawImage(emptyImage, op)
  }
docs: // DrawRect draws a rectangle on the given destination dst.
  //
  // DrawRect is intended to be used mainly for debugging or prototyping purpose.