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Introduction

Scratch was developed by the Lifelong Kindergarten group at the MIT Media Lab as a tool to teach design, thinking, collaborating, communicating, analyzing, and programing in a computer language.

When you open Scratch, this is what you will see:


This is the Scratch Interface or Integrated Development Environment (IDE).

The Scratch interface is divided into

1. The Blocks palette
2. The Script editor
3. The Stage

In the middle you will see the Blocks palette:

Each type of block is color-coded so that you can identify them in your scripts.

To create a script you drag, drop, and snap blocks into place in the Scripts area.


Text from veritas.eecs.berkeley.edu

Click the Presentation Mode button in the upper right hand corner when you want to present your project. To exit Presentation Mode, press the Esc key or the back arrow on the top left.

Click the arrow between the windows to switch between small and large Stage view.

You can use small Stage view to display Scratch on small screens or to expand the Scripts Area.

Click the minus, equal or plus sign to resize your blocks.

To find out what a block does, click on the help button.

To drag a stack, pick it up from the top block.

To delete a block, drag it from the script palette back towards the block palette.

Click on any block to run the block.

To stop a script, click the stop button at the top of the screen.

Exercises

1. Scratch is pretty intuitive. Complete this script:
   
   
   

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2. Sprites:
   1. Open Scratch
      
      

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   2. • Sprites, like the cat move and interact on the Stage.
        
        

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      • The Stage is 480 units wide and 360 units tall. It is divided into an x-y grid. The middle of the Stage has an x-coordinate of 0 and a y-coordinate of 0.
        
        

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      • To find out x-y positions on the Stage, move the mouse (the cursor) around and look at the mouse x-y display just below the Stage.
        
        
        

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   3. To find information about your sprite, click on the i
      
      
      
      
      
      Current Sprite Info shows a sprite's name, x-y position, direction, lock state, and pen state.
      
      
      
      
      
      You can type in a new name for the sprite.
      
      
      
      
      
      The sprite's direction indicates which direction the sprite will move when it runs a move block (0=up, 90=right, 180=down, -90=left). The blue line on the thumbnail shows the sprite's direction. You can drag this line to change the sprite's direction.
      
      
      
      
      
      
      Enable can drag in player to change the sprite's ability to be dragged.
      
      
      
      
      
      To save a sprite to a local file a , Ctrl+click the sprite on the Stage or in the Sprite List.
      
      This process saves the sprite as a .sprite file, which can then be imported into another project.
      
      

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   4. Drag a move block onto the script area
      
      
      

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   5. Click on the block.
      
      

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   6. Drag out a PLAY DRUM and snap it onto the MOVE block.
      
      
      

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   7. You can choose different drums from the pull-down menu.
      
      

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   8. Add another MOVE block. Attach it to the previous block. Click inside the block and type in a minus sign.
      
      

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   9. Click on any of the blocks to run the stack.
      
      

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   10. Add another PLAY DRUM block, then choose a drum from the menu. Click to run.
       
       

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   11. Drag out a FOREVER block and drop it on top of the stack. You want the mouth of the FOREVER to wrap around the other blocks.
       
       

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   12. Drag out a When Green Flag block and snap it on top.
       
       

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   13. Whenever you click the green flag, your script will start. Click the stop button at the top of the screen to stop.
       
       

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   14. Drag out a CHANGE EFFECT block.
       
       

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   15. Click on the block to see what it does.
       
       

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   16. Snap on a When space key pressed
       
       
       

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   17. You can choose a different key from the pull-down menu.
       
       

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3. Explain the difference of these two scripts:
   
   
   

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4. Create a flowchart that describes this situation:

   Move the cat sprite to the right by five steps as long as the location of the sprite is less than 268. If the sprite is greater than 268, move the sprite to -268.
   
   

   
   Then build the program to test your logic.
   
   

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5. This draws a square:
   
   
   Using a Repeat draw the following regular shapes:
   • Equilateral Triangle
   • Pentagon
   • Hexagon
   • Octagon
   • Circle
   Hint:
   Sum of Interior Angles = (n-2) x 180°
   Each Angle (of a Regular Polygon) =(n-2) x 180° / n
   
   How far in degrees does your character need to turn when you draw a triangle?
   How far in degrees does your character need to turn when you draw a pentagon?
   How far in degrees does your character need to turn when you draw a hexagon?
   
   

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6. Draw a five pointed star:
   
   How far in degrees does your character need to turn when you draw a star?
   
   

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7. 
   • Make a version where the tempo increases faster.
     

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   • Make another version where the tempo increases much-slower.
     

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   • Make another version where the tempo starts out fast and then decreases.
     

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   • Make another version where the tempo starts out slow, then gets fast, then gets slow again.
     

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8. Create a variable and name it note. Set note to 50. Make a script that plays every other note from 50-100.
   
   

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9. Make a new variable named Length. Start with length at 150. Draw the "Squiral" (Square+Spiral):
   
   
   

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10. Draw a picture (to draw faster, use the hide block):
    
    
    

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11. To get a random number between 1 and 10 (inclusive):
    
    Move your character randomly around the stage. Reverse the direction if you hit a wall. You should have 4 variables xSpeed, ySpeed, xDir, yDir
    
    

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More About Sprites

1. Each object in Scratch is called a sprite. To add a new sprite, click one of these buttons.
   
   

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2. Roll over the icons to see what they do
   
   

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3. To add a people sprite, double click on the first icon to open the Sprite Library:
   
   
   Go to the People Category
   
   
   

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4. Select Jodi.
   
   
   To see and edit a sprite's scripts, costumes, and sounds, click on the sprite's thumbnail in the Sprite List – or double-click on the sprite itself on the Stage.
   
   (The selected sprite is highlighted and outlined in blue in the Sprite List.)
   
   You can rearrange the sprites in the Sprite List by dragging the thumbnails.
   
   

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5. Make Jodi to say something.
   
   Make her to think something too!
   
   

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6. Here is how to get some user info and the do something with the answer:
   
   
   Make Jodi ask a question and then have her use the answer to say or think something about it.
   
   

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7. CTRL+clicking brings up a context menu. How would you delete the cat sprite?
   
   

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8. Explore the Image Effects. Use the pull-down menu to choose different effects.
   
   
   Then click the block to see the change. To clear the effects, click the Stop button.
   
   Create a code block that changes the effect, waits 1 second then changes the sprite back to the original state.
   
   

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9. Click the SOUNDS tab. Record your own sound. You could also import a sound file (MP3, AIF, or WAV format).
   
   
   

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10. Make Jodi to play your sound.
    
    

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11. Add a new sprite named cassy-d
    
    

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12. By switching between costumes, you can animate a sprite. Select Cassy Dance. To add (or see ) costumes, click the COSTUMES tab. Then if you want to add a costume click IMPORT to choose a second costume.
    
    Cassy comes with a few costumes already. To animate between them, select Next Costume block. What other code blocks should you add to create an animation where it looks like she moves through he dance 4 times?
    
    

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13. Just as a sprite can change its appearance by switching costumes, the Stage can change its appearance by switching backgrounds. To see and edit the scripts, backgrounds, and sounds associated with the Stage, click on the Stage icon at the left of the Sprite List.
    
    
    

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14. Change what the background looks like by clicking on the Background tab and then the Paint button. Click on the fill tool or use the paint tools.
    
    
    
    
    

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15. Save your work.
    
    

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Overview

1. To program a sprite, drag blocks from the Blocks Palette to the Scripts Area. To run a block, click on it.
   
   

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2. Create scripts (programs) by snapping blocks together into stacks. Click anywhere on the stack to run the whole script, from top to bottom.
   
   

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3. To find out what a block does, Ctrl+click on it, then select help from the pop- up menu.
   
   

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4. When you drag a block around the Scripts Area, a white highlight indicates where you can drop the block and form a valid connection with another block.
   
   

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5. To move a stack, pick it up from the top block. If you drag out a block from the middle of a stack, all of the blocks beneath it will come along with it. To copy a stack of blocks from one sprite to another, drag the stack to the thumbnail of the other sprite in the Sprite List.
   
   

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6. Some blocks have white editable text fields inside, such as move __steps . To change the value, click inside the white area and type in a number. You can also drop rounded blocks, like x position , inside these areas.
   
   

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7. Some blocks also have pull-down menus, such as set instrument to__. Click on the arrow to see the menu.
   
   

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8. To clean up the Scripts Area, Ctrl+click and select clean up from the menu. To export a screenshot of the Scripts Area, right-click and select save picture of scripts.
   
   

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9. To add a comment to the Scripts Area, Ctrl+click and select add comment. A yellow comment area will appear, and you can type in text.
   
   

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10. To resize the width of the comment area, use the handle on the right edge. Click the triangle at the top-left to collapse or expand the comment area.
    
    

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11. Comments can be added anywhere in the Scripts area, and you can move them around by dragging them.
    
    

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12. To attach a comment to a block, drag the comment on top of the block. To detach the comment, drag the comment away from the block.
    
    

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Modifying an existing program

1. Open Scratch
   
   

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2. Click on File>Open
   
   

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3. Click on the Examples button.
   
   
   

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4. Select Simulations and click OK
   
   
   

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5. Select Spinner and click OK to load the Spinner project.
   
   

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6. Follow the instructions on the screen and spin the arrow by clicking on the arrow.
   
   

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7. From the sprites list, click on Stage. From the scripts area, click the Backgrounds tab. Click Edit on background number 1 to open the Paint Editor.
   
   

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8. Select a unique color from the color palette, such as purple.
   
   

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9. Click on the paint bucket from the toolbar, then click on one of the triangles in the circle to change its color.
   
   

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10. Click OK to return to our project.
    
    

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11. Duplicate the existing background. Select the Stage sprite and click on the Backgrounds tab in the script area. Click the Copy button to duplicate background1.
    
    

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12. For background2, click the Edit button to open the Paint Editor. Click the Flip Horizontally button that is located above the editor window and click OK to exit the Paint Editor.
    
    

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13. Select the Spinner sprite from the list of sprites.
    
    

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14. From the Control palette, add the broadcast block to the script before the turn 5 degrees block. Click on the message drop-down list of the broadcast block and choose New.
    
    

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15. Type spin in the message name dialog box and click OK.
    
    

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16. Tell the Stage to listen for the broadcast message. Select Stage from the list of sprites.
    
    

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17. From the Control palette, add the when I receive block to the script area. Select spin from the message drop-down list.
    
    

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18. From the Looks palette, add the next background block to the script.
    
    

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19. Click on the spinner arrow on the Stage.
    
    

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20. Test
    
    

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21. Create blocks so that you get the background to change to background1 after the spinner stops spinning.
    
    

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22. Save.
    
    

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