/**
      * Sets the light position for drawing.
      */
    -Isomer.prototype.setLightPosition = function (x, y, z) {
    +Isomer.prototype.setLightPosition = function(x, y, z) {

    ...

       var yMap = new Point(point.y * this.scale * Math.cos(Math.PI - this.angle),
    -                    point.y * this.scale * Math.sin(Math.PI - this.angle));
    +  point.y * this.scale * Math.sin(Math.PI - this.angle));

No thanks :( In all seriousness, cool library. What standard does it follow? Can't seem to find that anywhere.