GameMaker Lesson: Dodge the Enemies

Random Movement, Lives, Collisions, and Game Over

Lesson Overview

In this project, you will create a simple Dodge the Enemies game in GameMaker.

The player will move around the room while several enemies move in random directions. Each time the player touches an enemy, the player will lose a life. When all lives are gone, the game will display a Game Over screen.

Learning Objectives

Create sprites and objects.
Move a player using the keyboard.
Give enemies random movement.
Detect collisions between objects.
Create and use a lives variable.
Display lives on the screen.
Create a Game Over screen.
Restart the game after losing.

Part 1 - Create the Project

Create a new GameMaker project.

Name the project:

PX_lastname_DodgeTheEnemies

Create 2 files and where to drop them:

file one: PX_lastname_DodgeTheEnemies.png (Screen print of the program inside the game maker ide)

file two: PX_lastname_DodgeTheEnemies.mp4 (Video of you playing the game. I need at least 7 seconds)

Be sure to drop off the two file into your google drive for class under 2026_27KleinCollins\your class name

Drop your two files into google classroom.

Use the GameMaker Language (GML) project type.

Part 2 - Create the Sprites

Player Sprite

Create a sprite named:

spr_player

Suggested size:

32 x 32

Your player could be:

A blue square
A spaceship
A person
A robot

Enemy Sprite

Create another sprite named:

spr_enemy

Suggested size:

32 x 32

Make the enemy easy to distinguish from the player.

Part 3 - Create the Player Object

Create an object named:

obj_player

Assign the sprite:

spr_player

Part 4 - Player Movement

Add a Step Event to obj_player.

var move_speed = 5;

if (keyboard_check(vk_left))
{
    x -= move_speed;
}

if (keyboard_check(vk_right))
{
    x += move_speed;
}

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

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

Keep the Player Inside the Room

Add this at the bottom of the Step Event:

x = clamp(x, 0, room_width);
y = clamp(y, 0, room_height);

Checkpoint 1 - Show Your Teacher

spr_player exists.
obj_player exists.
The arrow keys move the player.
The player stays inside the room.

Checkpoint Points: 10

Part 5 - Create the Enemy Object

Create an object named:

obj_enemy

Assign:

spr_enemy

Part 6 - Random Enemy Movement

Add a Create Event to obj_enemy.

speed = random_range(2, 5);
direction = irandom_range(0, 359);

Each enemy now receives a random speed and a random movement direction.

Part 7 - Make Enemies Bounce

Add a Step Event to obj_enemy.

if (x <= 0 || x >= room_width)
{
    hspeed = -hspeed;
}

if (y <= 0 || y >= room_height)
{
    vspeed = -vspeed;
}

Part 8 - Random Direction Changes

Add this code to the enemy Step Event:

if (irandom(100) == 0)
{
    direction = irandom_range(0, 359);
}

This gives each enemy a small chance to suddenly change direction.

Checkpoint 2 - Show Your Teacher

At least one enemy appears.
The enemy moves automatically.
The enemy starts in a random direction.
The enemy changes direction.

Checkpoint Points: 15

Part 9 - Create the Lives System

Add a Create Event to obj_player.

global.lives = 3;

The player begins with three lives.

Part 10 - Player and Enemy Collision

Add a Collision Event to obj_player with obj_enemy.

global.lives -= 1;

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

if (global.lives <= 0)
{
    room_goto(rm_gameover);
}

Each collision removes one life and moves the player back to the center.

Part 11 - Display the Lives

Create a new object:

obj_controller

The controller does not need a sprite.

Add a Draw GUI Event:

draw_set_font(-1);
draw_set_color(c_white);

draw_text(20, 20, "Lives: " + string(global.lives));

Checkpoint 3 - Show Your Teacher

The player starts with 3 lives.
Touching an enemy removes one life.
The player resets position after being hit.
Lives appear on the screen.

Checkpoint Points: 20

Part 12 - Create the Main Room

Create a room named:

rm_game

Suggested size:

960 x 540

Add:

1 obj_player
1 obj_controller
At least 5 obj_enemy objects

Part 13 - Create the Game Over Room

Create another room named:

rm_gameover

Create an object named:

obj_gameover

Place obj_gameover inside rm_gameover.

Part 14 - Draw the Game Over Message

Add a Draw GUI Event to obj_gameover.

draw_set_halign(fa_center);
draw_set_valign(fa_middle);

draw_set_color(c_red);

draw_text(
    display_get_gui_width() / 2,
    display_get_gui_height() / 2,
    "GAME OVER"
);

draw_set_color(c_white);

draw_text(
    display_get_gui_width() / 2,
    display_get_gui_height() / 2 + 50,
    "Press SPACE to Play Again"
);

Part 15 - Restart the Game

Add a Key Press - Space event to obj_gameover.

global.lives = 3;
room_goto(rm_game);

Checkpoint 4 - Show Your Teacher

Player movement works.
Enemies move randomly.
Collisions reduce lives.
Lives are displayed.
The Game Over room appears.
The spacebar restarts the game.

Checkpoint Points: 20

Part 16 - Increase the Difficulty

Experiment with enemy speed.

Original:

speed = random_range(2, 5);

Harder:

speed = random_range(3, 7);

Part 17 - Optional: Add More Enemies Over Time

Add this to the obj_controller Create Event:

alarm[0] = room_speed * 10;

Add an Alarm 0 Event:

instance_create_layer(
    irandom(room_width),
    irandom(room_height),
    "Instances",
    obj_enemy
);

alarm[0] = room_speed * 10;

Every 10 seconds, another enemy appears.

Part 18 - Optional Survival Score

Add this to the controller Create Event:

global.score = 0;
alarm[1] = room_speed;

Add an Alarm 1 Event:

global.score += 1;

alarm[1] = room_speed;

Display the Score

Add this to the controller's Draw GUI Event:

draw_text(
    20,
    50,
    "Score: " + string(global.score)
);

Display Final Score

Add this to the Game Over Draw GUI Event:

draw_text(
    display_get_gui_width() / 2,
    display_get_gui_height() / 2 + 100,
    "Final Score: " + string(global.score)
);

When restarting, reset the score:

global.lives = 3;
global.score = 0;

room_goto(rm_game);

Student Challenge Activities

Challenge 1 - Faster Enemies

Increase enemy speed.

Challenge 2 - More Lives

Change the game from 3 lives to 5 lives.

Challenge 3 - Different Enemy Types

Create:

obj_enemy_slow
obj_enemy_fast

Challenge 4 - Sound Effects

Add sounds when:

The player gets hit.
The game ends.
The game restarts.

Challenge 5 - Invincibility

Give the player two seconds of protection after getting hit.

Challenge 6 - Difficulty Levels

Create Easy, Normal, and Hard modes.

Troubleshooting

My Player Does Not Move

Make sure the movement code is inside the Step Event of obj_player.

My Enemies Do Not Move

Check the enemy Create Event:

speed = random_range(2, 5);
direction = irandom_range(0, 359);

My Player Instantly Loses All Lives

Move the player away from the enemy after a collision:

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

My Game Over Room Does Not Appear

Make sure the room is named exactly:

rm_gameover

I Get an Error About global.lives

Make sure the player Create Event contains:

global.lives = 3;

Game Requirements

A controllable player.
Arrow-key movement.
At least five enemies.
Random enemy movement.
Enemy bouncing or direction changes.
Player/enemy collision detection.
At least three lives.
Lives displayed on screen.
A Game Over screen.
A restart feature.

100-Point Grading Rubric

Requirement	Points
Player sprite and object	5
Player movement works correctly	10
Player stays inside the room	5
Enemy sprite and object	5
Random enemy movement	10
At least five enemies	5
Enemy bouncing/direction changes	10
Collision detection	10
Lives system works	10
Lives displayed on screen	5
Game Over system	10
Restart system	5
Game is playable and polished	5
Student added one original improvement	5
Total	100

Final Teacher Check

Before submitting your project, demonstrate:

Player movement
Random enemy behavior
A collision
Lives decreasing
Game Over
Restarting the game

Game Flow

START GAME ↓ Player moves with arrow keys ↓ Enemies move randomly ↓ Player dodges enemies ↓ Enemy collision ↓ Lose one life ↓ Lives > 0? / \ YES NO ↓ ↓ Continue GAME OVER ↓ Press SPACE ↓ Restart Game