/* Spiral.java (L.McCann, 2007/03/29)
 *
 * A short demo of the ACM Java Task Force's acm.graphics package's GTurle
 * class.  The idea can be traced back to Seymour Papert's "Mindstorms"
 * book.  Even small children can grasp the idea of a pen moving forward,
 * turning left or right, moving forward some more, etc.  Beyond introducing
 * computer programming to kids, the model is also useful for constructing
 * various figures, such as the spiral produced by this program.
 *
 * The JTF tutorial (Aug 2006 version) has a brief introduction to the
 * GTurtle class on pages 38-42.
 */


import acm.graphics.*;
import acm.program.*;
import java.awt.*;       // Needed for Color


public class Spiral extends GraphicsProgram
{
    static final int CARDINALITY = 150; // # members in segment length sequence
    static final int SCALE = 6;         // zoom factor; spreads segments apart

    public void run ()
    {
        GTurtle turtle;   // Drawing model; imagine a turtle wielding a pen

        System.out.println("\nA simple spiral to demo the GTurtle Class\n");

        turtle = new GTurtle( getWidth()/2, getHeight()/2 );  // window middle
        add(turtle);

        turtle.hideTurtle();          // turtle is visible by default
        turtle.setDirection(180);     // 0 deg = East, 90 = north, etc.
        turtle.penDown();             // draw when the turtle moves
        turtle.setColor(Color.BLACK); // draw black lines
        turtle.setSpeed(0.75);         // range is 0 .. 1

                // The length of the line segments matches the sequence
                // 1, 1, 2, 2, 3, 3, 4, 4, ..., which is easily generated
                // by the rule d(i) = i/2 + 1, where i = 0, 1, 2, ...

        for (int i=0; i<CARDINALITY; i++) {
            int distance = i/2 + 1;
            turtle.forward(distance*SCALE);  // SCALE = 1 --> solid spiral
            turtle.left(90);
        }

        System.out.println("The sprial is complete!\n");

    }

}