Pong Game in JavaFX using 90 lines of code

import java.util.Random; import javafx.animation.KeyFrame; import javafx.animation.Timeline; import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.canvas.Canvas; import javafx.scene.canvas.GraphicsContext; import javafx.scene.layout.StackPane; import javafx.scene.paint.Color; import javafx.scene.text.Font; import javafx.scene.text.TextAlignment; import javafx.stage.Stage; import javafx.util.Duration;

public class Pong extends Application { private static final int width = 800; private static final int height = 600; private static final int PLAYER_HEIGHT = 100; private static final int PLAYER_WIDTH = 15; private static final double BALL_R = 15; private int ballYSpeed = 1; private int ballXSpeed = 1; private double playerOneYPos = height / 2; private double playerTwoYPos = height / 2; private double ballXPos = width / 2; private double ballYPos = height / 2; private int scoreP1 = 0; private int scoreP2 = 0; private boolean gameStarted; private int playerOneXPos = 0; private double playerTwoXPos = width - PLAYER_WIDTH;

public void start(Stage stage) throws Exception { Canvas canvas = new Canvas(width, height); GraphicsContext gc = canvas.getGraphicsContext2D(); Timeline tl = new Timeline(new KeyFrame(Duration.millis(10), e -> run(gc))); tl.setCycleCount(Timeline.INDEFINITE); canvas.setOnMouseMoved(e -> playerOneYPos = e.getY()); canvas.setOnMouseClicked(e -> gameStarted = true); stage.setScene(new Scene(new StackPane(canvas))); stage.show(); tl.play(); }

private void run(GraphicsContext gc) { gc.setFill(Color.BLACK); gc.fillRect(0, 0, width, height); gc.setFill(Color.WHITE); gc.setFont(Font.font(25)); if(gameStarted) { ballXPos+=ballXSpeed; ballYPos+=ballYSpeed; if(ballXPos < width - width / 4) { playerTwoYPos = ballYPos - PLAYER_HEIGHT / 2; } else { playerTwoYPos = ballYPos > playerTwoYPos + PLAYER_HEIGHT / 2 ?playerTwoYPos += 1: playerTwoYPos - 1; } gc.fillOval(ballXPos, ballYPos, BALL_R, BALL_R); } else { gc.setStroke(Color.YELLOW); gc.setTextAlign(TextAlignment.CENTER); gc.strokeText("Click to Start", width / 2, height / 2); ballXPos = width / 2; ballYPos = height / 2; ballXSpeed = new Random().nextInt(2) == 0 ? 1: -1; ballYSpeed = new Random().nextInt(2) == 0 ? 1: -1; } if(ballYPos > height || ballYPos < 0) ballYSpeed *=-1; if(ballXPos < playerOneXPos - PLAYER_WIDTH) { scoreP2++; gameStarted = false; } if(ballXPos > playerTwoXPos + PLAYER_WIDTH) { scoreP1++; gameStarted = false; } if( ((ballXPos + BALL_R > playerTwoXPos) && ballYPos >= playerTwoYPos && ballYPos <= playerTwoYPos + PLAYER_HEIGHT) || ((ballXPos < playerOneXPos + PLAYER_WIDTH) && ballYPos >= playerOneYPos && ballYPos <= playerOneYPos + PLAYER_HEIGHT)) { ballYSpeed += 1 * Math.signum(ballYSpeed); ballXSpeed += 1 * Math.signum(ballXSpeed); ballXSpeed *= -1; ballYSpeed *= -1; } gc.fillText(scoreP1 + "\t\t\t\t\t\t\t\t" + scoreP2, width / 2, 100); gc.fillRect(playerTwoXPos, playerTwoYPos, PLAYER_WIDTH, PLAYER_HEIGHT); gc.fillRect(playerOneXPos, playerOneYPos, PLAYER_WIDTH, PLAYER_HEIGHT); }

}