GameMaker Pong

In this lesson, you will build a simple version of the classic Pong video game using GameMaker.

You will create two paddles, a moving ball, collision detection, scoring, and a system that resets the ball after a player scores.

Lesson Objectives

By the end of this lesson, you should be able to:

• Create two player-controlled paddles.
• Move paddles with the keyboard.
• Create a moving ball.
• Make the ball bounce off walls.
• Make the ball bounce off paddles.
• Keep score for both players.
• Reset the ball after a point.
• Display the score on the screen.

Game Requirements

Part 1 - Create the GameMaker Project

Create a new GameMaker project named:

Name the project:

PX_lastname_PongGame

Create these assets:

spr_paddle
spr_ball

obj_paddle_left
obj_paddle_right
obj_ball

obj_wall_top
obj_wall_bottom

obj_game

rm_pong

Part 2 - Create the Paddle Sprite

Create a sprite named:

spr_paddle

Make it a simple vertical rectangle.

Example size:

Width: 20
Height: 100

Set the origin to:

Middle Center

Part 3 - Create the Ball Sprite

Create a sprite named:

spr_ball

Make it a small square or circle.

Example size:

Width: 24
Height: 24

Set the origin to:

Middle Center

Part 4 - Create the Left Paddle

Create:

obj_paddle_left

Assign:

spr_paddle

Add a Create Event:

move_speed = 6;

Add a Step Event:

if (keyboard_check(ord("W")))
{
    y -= move_speed;
}

if (keyboard_check(ord("S")))
{
    y += move_speed;
}

Part 5 - Keep the Paddle on the Screen

Add this code to the bottom of the left paddle's Step Event:

y = clamp(
    y,
    sprite_height / 2,
    room_height - sprite_height / 2
);

The clamp() function prevents the paddle from moving outside the room.

Part 6 - Create the Right Paddle

Create:

obj_paddle_right

Assign:

spr_paddle

Add a Create Event:

move_speed = 6;

Add a Step Event:

if (keyboard_check(vk_up))
{
    y -= move_speed;
}

if (keyboard_check(vk_down))
{
    y += move_speed;
}

y = clamp(
    y,
    sprite_height / 2,
    room_height - sprite_height / 2
);

Part 7 - Create the Ball

Create:

obj_ball

Assign:

spr_ball

Add a Create Event:

ball_speed = 6;

direction = choose(30, 150, 210, 330);
speed = ball_speed;

The choose() function randomly selects one of several starting directions.

Part 8 - Create the Top and Bottom Walls

Create:

obj_wall_top
obj_wall_bottom

Create simple rectangle sprites for the walls or use another collision method.

Place one wall across the top of the room and one across the bottom.

Part 9 - Make the Ball Bounce Off the Walls

In obj_ball, add a Collision Event with:

obj_wall_top

Enter:

vspeed = abs(vspeed);

Add another Collision Event with:

obj_wall_bottom

Enter:

vspeed = -abs(vspeed);

Part 10 - Bounce Off the Left Paddle

In obj_ball, add a Collision Event with:

obj_paddle_left

Enter:

hspeed = abs(hspeed);

This makes the ball move to the right after hitting the left paddle.

Part 11 - Bounce Off the Right Paddle

Add a Collision Event with:

obj_paddle_right

Enter:

hspeed = -abs(hspeed);

This makes the ball move to the left after hitting the right paddle.

Part 12 - Improve the Paddle Bounce

You can make Pong more interesting by changing the ball's vertical speed depending on where it hits the paddle.

Left Paddle Collision

var difference = y - other.y;

hspeed = abs(hspeed);
vspeed += difference * 0.05;

Right Paddle Collision

var difference = y - other.y;

hspeed = -abs(hspeed);
vspeed += difference * 0.05;

Hitting near the top or bottom of a paddle changes the angle of the ball.

Part 13 - Create the Score Variables

Create an object named:

obj_game

Add a Create Event:

global.left_score = 0;
global.right_score = 0;

Place one instance of obj_game inside the room.

Part 14 - Detect When the Ball Leaves the Screen

Add a Step Event to obj_ball.

if (x < 0)
{
    global.right_score += 1;

    x = room_width / 2;
    y = room_height / 2;

    direction = choose(30, 150, 210, 330);
    speed = ball_speed;
}

if (x > room_width)
{
    global.left_score += 1;

    x = room_width / 2;
    y = room_height / 2;

    direction = choose(30, 150, 210, 330);
    speed = ball_speed;
}

If the left player misses, the right player receives a point.

If the right player misses, the left player receives a point.

Part 15 - Display the Score

Add a Draw GUI Event to obj_game.

draw_set_halign(fa_center);

draw_text(
    display_get_gui_width() / 4,
    30,
    string(global.left_score)
);

draw_text(
    display_get_gui_width() * 3 / 4,
    30,
    string(global.right_score)
);

The score for both players should now appear near the top of the screen.

Part 16 - Create the Pong Room

Open:

rm_pong

Place the following objects:

obj_paddle_left
obj_paddle_right
obj_ball
obj_wall_top
obj_wall_bottom
obj_game

Arrange them approximately like this:

+------------------------------------------+
|                                          |
| |                                      | |
| |                BALL                  | |
| |                                      | |
|                                          |
+------------------------------------------+

  Player 1                        Player 2

Part 17 - Test the Game

Run the game and test the controls.

Part 18 - Test the Scoring

Allow one player to intentionally miss the ball.

Verify that:

• The opponent receives one point.
• The ball returns to the center.
• Play continues.

Challenge 1 - Increase Ball Speed

speed += 0.25;

speed = min(speed, 12);

Challenge 2 - Add a Winning Score

winning_score = 10;

if (global.left_score >= winning_score)
{
    show_message("Player 1 Wins!");
    game_restart();
}

if (global.right_score >= winning_score)
{
    show_message("Player 2 Wins!");
    game_restart();
}

Challenge 3 - Add a Center Line

draw_line(
    display_get_gui_width() / 2,
    0,
    display_get_gui_width() / 2,
    display_get_gui_height()
);

Challenge 4 - Add Sound Effects

snd_paddle
snd_wall
snd_score

audio_play_sound(snd_paddle, 1, false);

Challenge 5 - Add Computer AI

if (obj_ball.y < y)
{
    y -= move_speed;
}

if (obj_ball.y > y)
{
    y += move_speed;
}

Final Game Checklist

• ☐ Left paddle moves with W and S
• ☐ Right paddle moves with the arrow keys
• ☐ Paddles stay inside the room
• ☐ Ball moves automatically
• ☐ Ball bounces off the top wall
• ☐ Ball bounces off the bottom wall
• ☐ Ball bounces off the left paddle
• ☐ Ball bounces off the right paddle
• ☐ Player 1 can score
• ☐ Player 2 can score
• ☐ Score appears on the screen
• ☐ Ball resets after a point
• ☐ Game runs without errors

Student Reflection

1. What variable controls the paddle speed?
2. What causes the ball to change direction?
3. What is the difference between hspeed and vspeed?
4. Why does the ball return to the center after a point?
5. What variables keep track of the two players' scores?
6. How could you make Pong more difficult?
7. What feature did you add that improved your game the most?

Extension Goal

After completing the basic Pong game, try adding one or more advanced features:

• Sound effects
• Increasing ball speed
• Different paddle sizes
• Power-ups
• Winning score
• Single-player computer AI
• Difficulty levels
• Start screen
• Replay button
• High-score system