Students will be able to...
- Demonstrate the difference between sprite and global variables
- Explain how cloning and prototyping simplify working with numerous similar sprites in the same program
- Create prototype sprites and clones of the prototype sprite
- Explain the difference between a "master" sprite and a "clone" sprite
- Do Now 5.2: Star Wars Troopers
- Lab 5.2 handout (Lots of Balls) (Download in Word) (Link to PDF)
- Test out the lab on student machines before class-- cloning in SNAP! can bring the web browser to a crawl on some machines
| Duration | Description |
|---|---|
| 5 minutes | Welcome, attendance, bell work, announcements |
| 15 minutes | Introductory discussion |
| 30 minutes | Lots of Balls lab |
| 15 minutes | Debrief and wrap-up |
- Introductory discussion
- Show students a brief video demonstrating space invaders (https://youtu.be/437Ld_rKM2s?t=15)
- Ask students to think about how we create all the “invaders”?
- Answer with current knowledge: make one invader sprite, and copy it many times while adjusting the copies as necessary
- Ask what might go wrong or be bad about this approach
- If anything in an invader changes, it will need to be changed many times
- Lots of sprites clogging up the program that are all basically doing the same thing - Introduce cloning as the automated way of doing the manual copying
- Demonstrate how to create a clone using
- Point out that clones inherit all aspects of the "master" or "prototype" sprite, including scripts
- Emphasize the importance of using
to ensure clones don't duplicate out of control
- Ask students to think about how we create all the “invaders”?
- Activity
* Students should complete the "Lots of Balls" lab
- This lab will largely duplicate the code shown in the lecture part of the lesson-- that's OK
- Students should focus on ensuring they are differentiating between "master" sprites and "clone" sprites, and that the stage is serving as the main "driver" for the program
- Advanced students can attempt to assign properties to clones (color, size, etc.) so that not all clones look alike. To do this, they will need to use a global variable to temporary hold the value that can be "claimed" by the clone.
- Struggling students should focus on just creating a single clone from the prototype and not worry about creating multiple clones.