// program to make a ball bounce around a DrawingPanel
//   using if/else and user input (Scanner)

import java.awt.*;
import java.util.*;

public class BouncingBall {
   public static void main(String[] args) {
      Scanner console = new Scanner(System.in);
      
      DrawingPanel panel = new DrawingPanel(600, 600);
      panel.setBackground(Color.CYAN);
      Graphics brush = panel.getGraphics();
      double x = 300, y = 300;
            
      System.out.print("Enter velocity (pixels per second): ");
      double velocity = console.nextDouble();
      System.out.print("Enter angle (degrees): ");
      double angle = console.nextDouble();
      System.out.print("Enter time (seconds): ");
      int seconds = console.nextInt();
      
      double xVel = velocity * Math.cos(Math.toRadians(angle));
      double yVel = -velocity * Math.sin(Math.toRadians(angle));

      brush.setColor(Color.RED);
      brush.fillOval((int)(x - 5), (int)(y - 5), 10, 10);
      panel.sleep(1000);
      
      for (int i = 0; i < 10*seconds; i++) {
         // turn old ball white
         brush.setColor(Color.WHITE);
         brush.fillOval((int)(x - 5), (int)(y - 5), 10, 10);
         
         // move ball
         x += xVel / 10;
         y += yVel / 10;
         
         // detect a bounce
         if (x <= 0 || x >= 600) {
            xVel = -xVel;
         }
         
         if (y <= 0 || y >= 600) {
            yVel = -yVel;
         }
         
         // redraw ball
         brush.setColor(Color.RED);
         brush.fillOval((int)(x - 5), (int)(y - 5), 10, 10);
         
         panel.sleep(100);
      }
   }
}