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Scratch
Creative Computing
Section 1
INTRODUCTION TO SCRATCH
Scratch
• Browser based
• Created at MIT
• Creative Computing – Using a tool to easily create a computer
program.
• Typically a drag-and-drop tool.
• Emphasizes creativity instead of programming syntax
• The ease of use allows beginners to be creative while
programming.
Section 1 Objectives
• By the end of this unit, students will:
• Understand the concept of computational creation, in the context
of Scratch
• be able to imagine possibilities for their own Scratch-based
computational creation
• become familiar with resources that support their computational
creation
•
Mr. Stoll’s account: sestoll99
Scripts and Commands
• Command – A statement that tells the computer what to do.
• In Scratch each command is called a “Block”
• Other scripting languages (block = set of commands)
• Script - list of commands that are executed by a certain
program or scripting engine.
• Scratch uses scripts
• Python is a scripting language
Sprite
• Sprite - an image and its
location on the stage
(screen).
• Three sprites on the stage
(screen)
• The Parrot sprite is
selected
• Work with Parrot Scripts
• What are score and
birdCounter? (top of screen)
The Scratch Interface
Script Menus (Motion Menu Selected)
Stage
Sprites
Motion Commands
Script Window
Creating Scripts (Lego Block Concept)
• Create scripts by snapping blocks together
Command blocks
applied to the sprite
Part of the Motion Menu
Part of the Sound Menu
Dancing Cat Demonstration
• Control – Repeat 10
Repeat the following four statements
10 times:
• Motion - Move 10 steps
• Sound - Play drum
• Motion - Move 10 steps
• Sound - Play drum
Sample Script (move and play drum repeatedly)
Tips For Using Scratch
• Drag a set of blocks from the top
• While dragging a block, everything below moves as well
• Separate blocks from the bottom
• Recommended:
• The green flag event is useful for
setting up your scene
• Programming commands are under the
tab.
• Most script commands apply to a specific Sprite
Sprite1 is selected
Time to Explore Scratch
1. Sign-up for Scratch: http://scratch.mit.edu
• Use account information you can remember.
• Forgetting this may hurt your grade in the future.
2. Play with Scratch
• Try to make something surprising happen to a sprite.
• Work together if desired!!!
• Be ready to discuss what you have learned.
Section 2
TALKING SPRITES
Making Sprites Talk
• Make sure you select the desired sprite first.
• The “when this sprite clicked” event is very useful
Mr. Stoll’s Example (About Me)
Click Here to Review the Project in Scratch
Create Your Own Project
• Create your own (About Me) project
• Make it more elaborate than mine.
• It is due at the beginning of the next class period
• Advanced students:
• Make it way better than mine.
About Me – Project Review
• Review student projects with class:
• Ask for volunteers
• Select some students randomly if necessary.
Section 3
ANIMATION – DANCE PARTY
Dance Party Project
• Dance Party - “a Scratch project in which sprites get down
with cool costumes and funky beats.”
• ie. claptrap from Borderlands
• For the next three slides we will create a Dance Party Scene.
We will:
• Define Sprite
• Define Costume
• Different images for a given sprite.
• Assemble code blocks so sprite dances when clicked.
Sprite
• Sprite - an image and its location on the
screen.
• Games have been using them for decades.
• Used to be hardware dependent.
• Sprite on Stage
• Sprite definition
• Press the
in the upper left
corner of the sprite definition to see
details about the sprite.
What is a Costume
• A sprite may have many costumes.
• Costumes are typically used for animation.
Dancing Ballerina
1. Press choose sprite from library button
2. Select a sprite from the library and press the OK button.
3. Create the following script:
Adding Music to Ballerina
• Separate simultaneous notes into
separate block sets.
• They run in parallel – At the same time,
when the ballerina is clicked.
• .4 secs is the same as .4 beats
• Synchronize music and animation.
• Drum 4 is the symbol.
• It plays at the end of the animation
Sprites and Costumes Review
• What is the difference between a sprite and a sprite’s
costume?
• When might you want to use a sprite?
• When might you want to use a costume?
Resetting Your Scene
• Initialize – To assign starting values.
• This is a set of code blocks for a
sprite. This block:
1. Executes when the green flag is pressed.
2. Moves the sprite to its starting point
3. Displays its initial costume (Picture1)
• There are several things you can
initialize in your scene.
• Most of them are in the
and
menus.
Incremental
• Incremental - increasing gradually by regular degrees or
additions.
• Always add and test small amounts of code at a time.
Assignment: Dance Party
• Dance party Assignment Requirements
1.
Sprites / Costumes – Select from one of these two options:
• Find a sprite (in Scratch or outside of Scratch) that has multiple
costumes.
• Take an existing sprite and modify it to have different costumes.
2.
Animate the sprite when the user clicks on it
• Move the sprite and change its costume.
3.
Play at least two notes each time the sprite changes costumes.
• Notes to be played at the same time must be in separate sets of
blocks.
• Review P. 49 of your Scratch Guide
• Everyone must have a unique project
Section 4
GAMES
Blocks for Games (Variables)
• Examples:
• health; moveSpeed; ammo; defensePoints
happiness (Sims); lives (old school games)
• Score Variable
• Initializing the Score
• Incrementing the Score
• Display/Hide Score
• See PP. 65 – 66 For More Information
Blocks for Games (Random)
• Very Useful:
•
•
•
•
Enemy appears in random place on screen.
Enemy starts with random # health points
Dice rolls for video Monopoly
Card drawn in a video card game
• Anybody Have an Example for us??:
• Sims
• Tetris
• Mario Kart
Blocks for Games (Visibility)
• The visibility of sprites
• Visible
• Invisible
• See PP. 65 – 66 For More Information
Blocks for Games (Timing)
• Timing Examples:
• Consistent game speed same on slow and
fast computers
• Change the image on the screen to display
the next frame of animation.
• See PP. 65 – 66 For More Information
Blocks for Games (Events)
• Event - an action or occurrence
detected by the program that may be
handled by the program.
• key press events – Code executes when
user clicks on the sprite.
• Initialization Event – Code that executes
when program is starting to run.
Green Flag
To Initialize Sprites and Variables
Blocks for Games (Comparisons)
• The player must not get a point unless
the Orange touches the Parrot without
touching the Cat sprite.
• Don’t increase the birdSpeed if it is
already moving at 15 or above.
• See PP. 65 – 66 For More Information
Blocks for Games (Collision Detection)
• Collision Detection – Detecting when one
sprite overlaps another sprite.
• If this sprite is touching specified sprite,
edge, or mouse-pointer.
• If this sprite is touching a specific color
• If a specified color on this sprite is touching
another color.
Games – Assignment (Make a
game)
• Review P 65 - 66 (blocks for games and collision detection)
Blocks for Games (Strings)
• I currently plan to wait to discuss
strings until we start working with
Python.
• See PP. 65 – 66 For More Information
Section 5
PROGRAMMING CONCEPTS
PROGRAMMING CONCEPTS
(How they relate to blocks)
• Decisions - Allows the program to compare two or more
values.
• Most programming languages use the "if" keyword.
• Loop – Repeat one or more commands until a condition is
met.
• Variable - Stores a value to be used later in the program.
• Random • Event - an action or occurrence detected by the program that
may be handled by the program.
• Etc.
Decision Structure
Scratch
Python
if mrStollsAge > 49:
print (‘You are old’)
if playerHealth < 10:
moveSpeed = 3
Sequential Structure
Scratch
Python
Print (‘Hello’)
moveSpeed = 3
xPosition = xPosition + 10
yPosition = yPosition + 10
Loops
Scratch
Python
while guessesTaken < 6:
Command
Command
etc.
while True:
command
command
etc.
Variables
Scratch
Python
Score = 17
birdCounter = 30
birdSpeed = 5
Random
Scratch
Numbers
Python
random.randint(1, 10)