1. Create a Halloween Computer Game in Scratch
Stephanie Smullen and Dawn Ellis
Barb Ericson
October 2008

2. Start up Scratch Click on the Scratch icon
This set of slides assumes that you have already explained how to connect tiles together (when you see the white line). And have explained that the center of the window is 0,0.

3. The Scratch Stage
The Scratch stage is 480 pixels wide and 360 pixels high.
180
-240
0,0
240
at the center of the stage
-180

4. Delete the Cat
Click on the scissors and your cursor turns to scissors and then click on the cat to delete it

5. Add the Witch
Click on the button with the picture of folder with a star in it
if you hover over it, it says "Choose new sprite from file"

6. Select the Fantasy Folder

7. Scroll to the Witch
Click on the witch and then OK

8. Resize Your Sprite!
You can make your sprite larger or smaller by using the “grow sprite” or “shrink sprite” icons.
You click on one of these icons, then click on your sprite until it is the size you’d like.
shrink
grow

9. Move the Sprite
Select (click on the arrow and then on the sprite) and click and drag the sprite to the bottom of the window

10. Respond to Arrow Keys
Click on Control (orange) and then drag out "when space key pressed"

11. Respond to Right Arrow
Click on down arrow next to space and select right arrow
Click on Motion (blue) and drag out "move 10 steps"

12. Change the move amount Click on the 10 Type 5 and press enter
it will highlight in blue
Type 5 and press enter

13. Respond to Left Arrow Click on Control (orange)
Drag out "when space key pressed"
Change "space" to "left arrow"
Click on Motion
Drag out "move 10 steps"
Change it to -5 (to move left)
Click on the stage and try out the left and right arrow keys
Does the sprite leave the window?

14. Paint a Pumpkin Click on the paint brush and star
It will say "Paint new sprite" if you hover over it

15. Use the Paint Editor
Click on the Ellipse tool

16. Select a Color

17. Draw the Ellipse Click and drag to create the ellipse
Use the paint brush to add eyes and a mouth to
make the
pumpkin
Then click on
"OK"

18. Size the pumpkin as desired and move it to the top
Click and drag the pumpkin to the top of the window

19. Make the Pumpkin Fall
When the green flag is clicked we want the pumpkin to start at the top and fall down
Click on Control (orange)
Drag out "When green flag clicked"

20. Start the Pumpkin Click on Motion (blue) Drag out “go to x # y # “
this will always start the pumpkin at the current position
Drag out "point in direction 90"
and change it to 180 (down)

21. Make the pumpkin fall Click on Control (orange) Click on Motion (blue)
drag out "forever"
Click on Motion (blue)
drag out "move 10 steps"
change it to 1 step
Try it out!

22. Catch the pumpkin!
If the distance from the center of the pumpkin to the sprite is less than the half the size of the pumpkin then it is caught
Let's track how many pumpkins we have caught with a score

23. Track the score When we start the game set the score to 0
Click on Variables (red)
Click on Make a Variable
Name it score

24. Set score to 0 Highlight the pumpkin sprite Drag the “forever” down
Drag out "set score to 0“
Drag the “forever” back up
Notice the score showing on the window

25. Did we catch the pumpkin?
From Control drag out “if”
We will check if the distance to the sprite is less than half the pumpkin size
Click on Number (green) and drag out "blank < blank"

26. Distance to sprite Click on Sensing (light blue)
Drag out "distance to blank"
Change it to Sprite1 (or the name of your sprite)

27. Half the Size of the pumpkin
Click on Number
Drag out "blank / blank"
From Looks drag out “size”
Type on the second blank and type 2

28. Increment the score Click on Variables Try it out!
drag out “change score by 1”
Put it inside the “if” block
Try it out!
is this what you expected?
The score increases each time the ball moves and is still touching the sprite. We really want the ball to move back to the top of the window instead once we catch it.

29. Reset the pumpkin Once you catch the pumpkin
move it back to the top of the window
this time to a random x value
between the left edge and right edge
Click on Motion and drag out “go to x # y #"

30. Pick a random X value Click on Number drag out "pick random 1 to 10"
drop on the x value after “go to x:”
change the 1 to -235 and change 10 to 235
change the y value to match the y in the first “go to x # y #”

31. Adding Losing
If the sprite doesn't catch the pumpkin it just gets stuck at the bottom of the screen
Let's tell the player that he or she lost

32. Add text sprite Click on the Paint new sprite button
Click on the T for text
Move the square to where you want the text
Type You Lost!

33. Hide the sprite Click on Control Click on Looks
drag out "when green flag clicked"
Click on Looks
drag out “hide”

34. Check if lost If the pumpkin hits the bottom of the window
the player has lost
Click on Control
drag out “if”

35. Check if at bottom Click on Numbers Click on Motion
Drag out "blank < blank"
Click on Motion
drag out "y position"
Click on the last blank in the last “if”
type in -175

36. Broadcast a message Sprites communicate by passing messages
One sprite broadcasts the message
Other sprites can listen for it and react to it when they receive it
Click on Control
drag out "broadcast blank"
click on the drop down arrow
next to new – name it lost
Add “stop script”
to stop the forever loop

37. Receive Lost Click on the text sprite Click on Control Click on Looks
drag out "when I receive blank"
click on the down arrow and select lost
Click on Looks
drag out “show”
drag out “stop all”
to stop all scripts
The stop all will stop all the scripts from executing.

38. Add a Background Click on stage Click on the Backgrounds tab
Click on import
Select a new background

39. Create Instructions
Click on the Show Project Notes in the upper right corner
Add the author and instructions
Press OK

40. Test your game Click the green flag
If you want, adjust the speed of the pumpkin
Modify the sprites using the “Costume” tab
Save your game with the “Save” button

41. Share your game You can share your projects at the scratch web site
Click on the Share! button
You can also download other projects and see how they were created

42. Other Ideas Add a sound when you lose Add the ability to win
You may need to add a "stop script" to the script for the pumpkin after you send the lost message
Add the ability to win
When you reach a certain score
Track the amount of time it takes as well
Speed up the pumpkin over time
Add more sprites to catch
Add a sprite to avoid (like a ghost)
killer sprite

43. Concept Summary Variables Forever loops Conditionals – ifs
can hold values and can change value
Forever loops
repeat all the commands inside of them one at a time until the script is stopped
Conditionals – ifs
only execute the body of the if when the condition is true
Sprites can pass messages
and receive them
Sprites can react to events
like clicking the green flag and pressing the left or right arrow keys
Sprites can have several scripts, costumes, and sounds