30 min intro to Scratch

1. 30 min intro to Scratch A Quick-and-Dirty approach Leaving lots of exploration for the future. (5 hour lesson plan available) 30 min Scratch July 2009

2. Objectives of Scratch unit • Intro to visual programming environment • Intro to programming with multimedia • Story-telling | music-making | game-making • Intro to programming concepts objects and attributes sequence, repetition conditions, events, I/O For instructors 30 min Scratch July 2009

3. Secondary objectives • Increase student skills with computers • Increase student interest in programming • Student achievement on fun project • Learn Cartesian coordinates, distance computations, etc. 30 min Scratch July 2009

4. Computer scientists • Create solutions to problems using computers • Study information • Invent algorithms • Write programs to implement the algorithms • Reuse a lot of existing program and machine parts 30 min Scratch July 2009

5. Start scratch and let’s go! • Click on the cat icon • Or, find “scratch” under “Programs” • When home, download from www.scratch.mit.edu • Scratch programming environment comes up quickly 30 min Scratch July 2009

6. Click on the “Looks” button at the top left. 30 min Scratch July 2009

7. Major components • At right: the stage with sprite[s] or objects or actors • At left: operations and attributes for the sprites • Center: scripts or program[s] for the behavior[s] of the sprites • Your sprites are actors that you direct with your scripts 30 min Scratch July 2009

8. Let’s implement an algorithm to average two numbers • Make a variable “number1” (click and drag and set) • Make another one “number2” 30 min Scratch July 2009

9. Compute average first as sum • Make variable average • Drag a “set operation” to script area • Drag a + operation • Drag variables number1 and number2 to parameters • Click to execute 30 min Scratch July 2009

10. Average script as 4 operation sequence. Change the two numbers and click the sequence to execute the block again. 30 min Scratch July 2009

11. But Scratch computes with multimedia – color, sound, … • Can make cartoons • Can create stories • Can create video games 30 min Scratch July 2009

12. The “hello” script • Can do it in 57 languages – java, C++, … Scratch • Easy in Scratch: select “Looks” operations and drag the “hello operation” onto your center panel. • Then double click on this “lego block”: check your sprite behavior at the right Your very first Scratch program! 30 min Scratch July 2009

13. Make the cat 50% larger • Select “Looks” operations • Drag the “change size” operator into your script • Click and edit for a 50% change (increase) • Double click your one operation script • Did your cat sprite get 50% bigger? 30 min Scratch July 2009

14. Scripting a sequence of ops • Do ops in the following order by dragging operation blocks into a single connected block • Say hello • Move 200 steps forward • Grow 50% bigger • Make the “meow sound” 30 min Scratch July 2009

15. Some new operations • color change (Looks) • wait (Control) • move (Motion) 30 min Scratch July 2009

16. Starting a looped script 30 min Scratch July 2009

17. Exercise: write a script to • Make the cat move along a square path • Say “hi” at all four corners • Wait 3 seconds at each corner • Change color at all four corners • Double size when back to the original starting location. • Say “That’s all folks” when done. 30 min Scratch July 2009

18. Elements of Scratch: objects • Colors • Sounds • Locations in 2D space • Sprites • Costumes • Variables (to remember the state of things) • Events: that are broadcast for communication 30 min Scratch July 2009

19. Elements of Scratch: control • Sequence of operations • Loops or repetition • Detecting events (key or mouse pressed, sprites overlapping each other, sprites hitting edge of stage, sensor giving value) 30 min Scratch July 2009

20. Loop constructs in Scratch • Repeat N times • Repeat forever • Repeat forever if some condition exists (suppose I’m a sprite wandering about this lab until someone asks a question) 30 min Scratch July 2009

21. Conditions can be checked • Do something if sprite k hits sprite m • Do something if a certain key is pressed • Do something is some variable takes a certain value 30 min Scratch July 2009

22. Interacting with your sprite or story • Using mouse • Entering a character • Asking the user a question 30 min Scratch July 2009

23. Sprite follows the mouse Try changing the number of steps or the wait time. 30 min Scratch July 2009

24. Play and examine MadLib • Choose the “file” option at the top of the window • Choose “open”, then “examples” • Choose “stories” • Choose “MadLib” and then read the authors instructions • Click OK, wait for load, click green flag 30 min Scratch July 2009

25. About the MadLib story • How many actors (sprites)? • What is the role of the girl? • How are the answers you give 'remembered' and then used in later actions? • What is the role of the little whale? • What makes the little whale flip around? • What makes the big whale spout? 30 min Scratch July 2009

26. Sprites can interact with each other • Can detect when colors overlap in space • Can detect when sprites bump into edge of the stage • See “bouncing balls” example under Simulations under Examples • Interact with this simulation • Check out the rather complex scripts 30 min Scratch July 2009

27. Check out the break dance • Open examples; music and dance; break dance • How does break dancing begin? • What are the roles of the sprites? • What events are in the scripts? • What should happen when the boom box is clicked? 30 min Scratch July 2009

28. Experiment with Scratch as time permits • Try your own scripts: make moves, sounds, interactions in simple cases • Try the examples and learn what makes them work • Download Scratch on your own machine and experiment some more • Direct a story; or a simulation; or create a video game. 30 min Scratch July 2009