btnCalc.onRelease = function(){
//calculate DX and DY from angle and length
//use vector projection to get DX and DY
//offset the angle
degrees = angle -90;
//convert to radians
radians = degrees / 180 * Math.PI;
//get DX and DY (normalized: length is one)
dx = Math.cos(radians);
dy = Math.sin(radians);
//compensate for speed
dx *= length;
dy *= length;
} // end btnCalc