code: function(referencePoint, otherPoint) {
      if (this.yDown) {
        if (otherPoint.y > referencePoint.y) {
          otherPoint = {
            x: otherPoint.x,
            y: referencePoint.y - (otherPoint.y - referencePoint.y)
          }
        } else if (otherPoint.y < referencePoint.y) {
          otherPoint = {
            x: otherPoint.x,
            y: referencePoint.y + (referencePoint.y - otherPoint.y)
          }
        }
      }
  
      var delta = vec2d(otherPoint).minus(vec2d(referencePoint))
      var weird = radiansToWeird(delta.angle())
      var compass = weirdToCompass(weird)
  
      for (var i = 0; i < this.slices.length; i++) {
        if (this.slices[i].contains(compass)) {
          return this.slices[i].number
        }
      }
    }
docs: Tells what slice some point is in relative to a reference point.
  
  @param referencePoint Object with x and y properties
  @param otherPoint Object with x and y properties
  @return zero based slice number