/*************************************************************************
 *  Compilation:  javac EarthSimple.java
 *  Execution:    java EarthSimple
 *  Dependencies: StdDraw.java
 *
 *  Skeleton code for the solris system.
 *
 *  % java EarthSimple
 *
 *************************************************************************/

public class EarthSimple { 
    public static void main(String[] args) {

        // set the scale of the coordinate system
        StdDraw.setXscale(-1.0, 1.0);
        StdDraw.setYscale(-1.0, 1.0);

        // initial values
        double earthAngle = 0;

        // main animation loop
        while (true)  {
            // clear the background
            StdDraw.setPenColor(StdDraw.BLACK); 
            StdDraw.filledSquare(0, 0, 2);
 
            // compute the location of the Earth
            double earthX = 0.75 * Math.cos(earthAngle);
            double earthY = 0.75 * Math.sin(earthAngle) * 0.25;
            earthAngle += 2*Math.PI/365;  
            earthAngle = earthAngle % (2 * Math.PI);

            //
            // You need to add codes to the following code
            // to include the Moon
            //

            if (earthAngle < Math.PI)
            {
                // the Earth is behind the Sun 
                StdDraw.setPenColor(StdDraw.BLUE);
                // draw the Earth
                StdDraw.filledCircle(earthX, earthY, 0.15); 
                StdDraw.setPenColor(StdDraw.RED);
                // draw the Sun
                StdDraw.filledCircle(0, 0, 0.3); 
            }
            else
            {
                // the Earth is in front of the Sun
                StdDraw.setPenColor(StdDraw.RED);
                // draw the Sun
                StdDraw.filledCircle(0, 0, 0.3);
                StdDraw.setPenColor(StdDraw.BLUE);
                // draw the Earth
                StdDraw.filledCircle(earthX, earthY, 0.15);
            }

            // delay for one day (for us 10ms)
            StdDraw.show(10); 
        } 
    } 
}