Lesson 4: Shapes and Randomization
Overview
In this lesson students continue to develop their familiarity with Game Lab by manipulating the width and height of the shapes they use to draw. The lesson kicks off with a discussion that connects expanded block functionality (e.g. different sized shapes) with the need for more block inputs, or "parameters". Students learn to draw with versions of ellipse()
and rect()
that include width and height parameters. They also learn to use the background()
block. At the end of the progression students are introduced to the randomNumber()
block. Combining all of these skills students will draw a randomized rainbow snake at the end of the lesson.
Purpose
This lesson gives students a chance to slightly expand their drawing skills while continuing to develop general purpose programming skills. They will need to reason about the x-y coordinate plane, consider the order of their code, and slightly increase their programs' complexity. The randomNumber()
block is important for the next lesson where students learn to store values using variables. This lesson should be focused primarily on skill-building. If students are able to complete the rainbow snake independently, then they have the skills they'll need for the coming lessons.
Assessment Opportunities
-
Use and reason about drawing commands with multiple parameters
See level 7 in Code Studio.
-
Generate and use random numbers in a program
See level 11 in Code Studio.
Agenda
Warm Up (5 min)
Activity (40 min)
Wrap Up (5 min)
View on Code Studio
Objectives
Students will be able to:
- Use and reason about drawing commands with multiple parameters
- Generate and use random numbers in a program
Preparation
- Review the level sequence in Code Studio
Vocabulary
- Parameter - An extra piece of information passed to a function to customize it for a specific need
Introduced Code
Teaching Guide
Warm Up (5 min)
Shapes of Different Sizes
Discussion Goal
Goal: This discussion introduces the vocabulary word "parameter" and also helps motivate their use. Students will be seeing versions of the ellipse()
and rect()
block in this lesson that have additional parameters, as well as the randomNumber()
block which has two parameters. Students may say they want inputs for the size of the shapes, their color, etc. During this conversation tie the behaviors the students want to the inputs the block would need. For example, if you want circles to be a different size the block will need an input that lets the programmer decide how large to make it.
Prompt: Our ellipse
and rect
blocks each have two inputs that control where they're drawn - the x and y position. If you wanted these commands to draw a wider variety of rectangles and ellipses, what additional inputs might you need to give these blocks? What would each additional input control?
Discuss: Students should brainstorm ideas silently, then share with a neighbor, then discuss share out with the whole class. Record ideas as students share them on the board.
Remarks
This was a good list of ideas. If we want our blocks to draw shapes in different ways they'll need more inputs that let us tell them how to draw. The inputs or openings in our blocks have a formal name, parameters, and today we're going to be learning more about how to use them.
Activity (40 min)
Programming Images
Transition: Move students onto Code Studio
Share: If some students have taken extra time to work on their projects, give them a chance to share their more complex rainbow snakes. Focus conversation on which parameters students are manipulating or randomizing to create their drawings.
Wrap Up (5 min)
Journal
Prompt: Have students reflect on their development of the five practices of CS Discoveries (Problem Solving, Persistence, Creativity, Collaboration, Communication). Choose one of the following prompts as you deem appropriate.
-
Choose one of the five practices in which you believe you demonstrated growth in this lesson. Write something you did that exemplified this practice.
-
Choose one practice you think you can continue to grow in. What’s one thing you’d like to do better?
-
Choose one practice you thought was especially important for the activity we completed today. What made it so important?
- Lesson Overview
- Student Overview
- New Shapes
- 2
Student Instructions
Rectangle Size
These rect
blocks have two more parameters that you can use to control the size. Notice that the noStroke()
block turns off the stroke (border) for shapes.
Do This
Student Instructions
Do This
- Write code that makes an orange ellipse behind the green one.
- Don't worry about the exact size as long as the green ellipse is entirely inside the orange one.
Student Instructions
Background
Sometimes you'll want to fill the entire screen with a color. For that, you can use background
. It covers everything on the screen with the color you choose.
Do This
- Run the code to see
background
work. - Change the background from yellow to orange.
Challenge: There is a purple square that is covered up by the background. Can you change the order of the code so you can see both the purple and blue squares?
Student Instructions
Background
background()
will draw on top of everything already in your drawing, so it's important to think about the order of your code.
Do This
- Use
background()
to make a "black" background behind the green circle.
Student Instructions
Debug - Using 4 Parameters
This program uses the four parameter version of rect()
and ellipse()
to draw a simple scene.
Do This
- Debug this program and correct the error so that the grass extends across the entire bottom.
- Hint: You only have to change one number. Which parameter makes your rectangle (the grass) wider?
Assessment Opportunities
Use arguments to change the way a method or command runs.
Extensive Evidence
The programmatic drawing appears exactly as it does in the example.
Convincing Evidence
The programmatic drawing is approximately the same as that in the picture, and the cloud's width and height have been changed.
Limited Evidence
The cloud's height, width, or position has been changed, but it may not be wider than it is tall, or it may be moved to somewhere else on the screen.
No Evidence
No changes have been made to the code, or the changes are unrelated to the instructions.
Student Instructions
Debug - Using 4 Parameters
Now that the grass is working, let's add a cloud to the sky. Unfortunately, it looks a little funny right now.
Do This
- Debug this program to make the cloud wider than it is tall, like in the image.
- Hint: You'll need to change two parameters. Which ones set your cloud's width and height?
- Shapes and Parameters
- Student Overview
- More Parameters
- 9
Student Instructions
Random Numbers
randomNumber()
chooses a random number between a minimum and maximum value. You can use this code instead of writing in the specific number. If you make your drawings with random numbers it will look a little bit different every time you run your program.
Do This
- Run the program several times to see how it works.
- Change the numbers inside
randomNumber
and run the code again a few times to see what changes.
Student Instructions
Random Numbers
Here's the same sun from last time. Right now only the x-coordinate is random, but you can make the y-coordinate random, too.
Do This
- Use
randomNumber()
for the ellipse's Y parameter so the circle is drawn in a random Y position, too. - As long as your circle is appearing at random X and Y positions, you can move on.
Assessment Opportunities
Generate and use random numbers in a program, use arguments to change the way a method or command runs.
Extensive Evidence
All circles have reasonable horizontal positions, different colors, and appear at random vertical positions, and some circles have a random size.
Convincing Evidence
All circles have reasonable horizontal positions, different colors, and appear at random vertical positions
Limited Evidence
At least one student-created circle has a new color, appears at a random vertical position, and has a different horizontal position than any others.
No Evidence
No student produced circles, or any new circles share a color or horizontal position with circles produced by the original code.
Student Instructions
Rainbow Snake
This program draws a very rare breed of rainbow snake. To make the snake draw differently every time you'll need to use random numbers.
Do This
- Run the program several times to see how the starter code works.
- Add at least three new different colored circles to your rainbow snake.
- Use
randomNumber()
to make the rest of the snake's body move up and down like the first three.
Challenge: Can you make size of some of the circles random, too?
- Random Numbers
- Student Overview
- Levels
- Extra
Student Instructions
Free Play
Use what you've learned to create whatever you like. When you're finished, you can click to send your creation to a friend, or to send it to your Projects Gallery.
Standards Alignment
View full course alignment
CSTA K-12 Computer Science Standards (2017)
AP - Algorithms & Programming
- 2-AP-13 - Decompose problems and subproblems into parts to facilitate the design, implementation, and review of programs.
- 2-AP-17 - Systematically test and refine programs using a range of test cases.
- 2-AP-19 - Document programs in order to make them easier to follow, test, and debug.