// 2/23/2000 TYan
// graphical version of balls

import java.awt.*;

class Ball {
    Color color;
    double pos;
    double velocity;

    // create a Ball with name n, position p, velocity v
    Ball(Color c, double p, double v) {
        color = c; pos = p; velocity = v;
    }
    
    // draw using specified scale factor
    void paint(Graphics g, double scale) {
        int diameter = (int) scale;
        g.setColor(color);
        g.fillOval((int) (scale*pos), diameter/2, diameter, diameter);
    }

    // move the ball with acceleration a, bouncing as appropriate
    void move(double a) {
        pos += velocity;
        if (pos < 0) { 
            velocity = -velocity; 
            pos = -pos;
        }
        velocity += a;
    }
}

class World1D extends Frame {
    double accel = -.2;
    double scale;
    int steps;

    // create a world of size w and scale factor s (hence, width w*s)
    // that draws t time steps
    public World1D(double w, int t, double s) {
        scale = s;
        steps = t;
        show(); // show; apparently needed to getInsets
        setSize(getInsets().left+getInsets().right+(int)(s*w),
               getInsets().top+getInsets().bottom+(int)(s*(1+t)));
        setBackground(Color.white);
    }

    // safely create and draw all the balls
    // NOTE: In Project 4, you do NOT want to (re)create molecules
    //       each time you draw.
    synchronized public void mypaint(Graphics g) {
        Ball a = new Ball(Color.red, 15, 4);
        Ball b = new Ball(Color.green, 28, .5);
        Ball c = new Ball(Color.blue,  3,-2);
        g.translate(getInsets().left,getInsets().top);
        g.clearRect(0,0,getSize().width,getSize().height);
        for (int i = 0; i <= steps; i++) {
            g.translate(0,(int) scale);
            a.paint(g,scale);
            b.paint(g,scale);
            c.paint(g,scale);
            a.move(accel);
            b.move(accel);
            c.move(accel);
        }
    }

    // draw all the balls
    public void paint(Graphics g) {
        mypaint(g);
    }
}

public class graphics0 {
    public static void main(String[] args) {
        World1D w = new World1D(80,100,6);
    }
}