Space Invaders

In this exercise, you will learn how to implement player movement for the spaceship in Space Invaders. We'll use the left and right arrow keys to control the spaceship's horizontal movement.

Step 1: Creating the Player Sprite

Step 2: Implementing Movement

when green flag clicked
forever
  if <key [left arrow v] pressed?> then
    change x by (-5)
  end
  if <key [right arrow v] pressed?> then
    change x by (5)
  end
end
                          

This script continuously checks if the left or right arrow keys are pressed and moves the spaceship accordingly.

Step 3: Limiting Movement

To prevent the spaceship from moving off-screen, we need to add boundary checks.

when green flag clicked
forever
  if <key [left arrow v] pressed?> and <(x position) > (-230)> then
    change x by (-5)
  end
  if <key [right arrow v] pressed?> and <(x position) < (230)> then
    change x by (5)
  end
end
                          

This updated script checks the spaceship's position before moving, ensuring it stays within the screen boundaries.

In this exercise, we'll create multiple enemy invaders using cloning and implement their movement pattern.

Step 1: Creating the Enemy Sprite

Step 2: Cloning Enemies

when green flag clicked
hide
repeat (5)
  create clone of [myself v]
  change x by (50)
end
                          

This script creates 5 clones of the enemy, spacing them out horizontally.

Step 3: Enemy Movement

when I start as a clone
show
forever
  move (2) steps
  if <touching [edge v]?> then
    turn (180) degrees
    change y by (-10)
  end
end
                          

This script makes each enemy clone move back and forth, dropping down a level when it reaches the edge of the screen.

In this exercise, we'll implement collision detection between the player's bullets and the enemy invaders.

Step 1: Creating Bullets

when green flag clicked
hide

when [space v] key pressed
create clone of [myself v]

when I start as a clone
go to [Spaceship v]
show
repeat until <<touching [edge v]?> or <touching [Enemy v]?>>
  change y by (10)
end
if <touching [Enemy v]?> then
  broadcast [hit v]
end
delete this clone
                          

Step 2: Handling Enemy Hits

when I receive [hit v]
if <touching [Bullet v]?> then
  delete this clone
end
                          

This script deletes the enemy clone when it's hit by a bullet.

In this final exercise, we'll implement a scoring system and game over conditions.

Step 1: Setting Up the Score

when green flag clicked
set [Score v] to (0)
                          

Step 2: Increasing the Score

when I receive [hit v]
if <touching [Bullet v]?> then
  change [Score v] by (1)
  delete this clone
end
                          

Step 3: Game Over Condition

when green flag clicked
forever
  if <touching [Enemy v]?> then
    broadcast [game over v]
    stop [all v]
  end
end
                          

This script ends the game if an enemy reaches the spaceship.

Homework: Complete Your Space Invaders Game!

Now that you've learned the foundational components of Space Invaders, your homework is to complete the game! Here are some tasks to guide you:

• Implement all the components we've covered in class.
• Add a start screen with instructions.
• Create multiple levels with increasing difficulty.
• Add sound effects for shooting and enemy destruction.
• Implement a high score system.
• Be creative! Add your own unique features to make the game more exciting.

Remember to test your game thoroughly and have fun creating it!