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Lessons

    Aligns to:

    (Also available in WeScheme)

    Students define functions that control the movement of the target and danger in their games.

    Lesson Goals

    Students will be able to:

    • Apply the Design Recipe to create a function given the constraints of a word problem.

    • Explain the basics of animation.

    Student-Facing Lesson Goals

    • Let’s learn about animation.

    • Let’s use the Design Recipe to help us breakdown word problems that will get our game characters moving!

    Materials

    Key Points for the Facilitator

    • Encourage students to take their time in understanding why we want to fix update-danger and update-target.

    • Students might be confused as to how the animation is working. The make-game function at the bottom of the file has many inputs - including update-danger and update-target. make-game takes in all those inputs, including the functions we’ll write, and creates the interactive window that we see when we click the "Run" button!
    Glossary
    coordinate

    a number describing an object’s location

    design recipe

    a sequence of steps that helps people document, test, and write functions

    domain

    the type or set of inputs a function expects, i.e., the independent variable(s) that govern the output of the function

    function

    a relation from a set of inputs to a set of possible outputs, where each input is related to exactly one output

    range

    the type or set of outputs that a function produces, i.e., the dependent variable(s)

    🔗Animation 45 minutes

    Overview

    Students connect the behavior of functions with changing coordinate values, ultimately leading to animation.

    Launch

    • How does a flip-book animation work?

      • Each page of the book is slightly different, and the pages go so fast that the motion looks smooth.

    • Why do we see movement from still images?

      • Our eyes fill in the gaps between rapidly changing images.

    • How might this apply to our game?

      • If we change image coordinates a little bit at a time, they will appear to move.

    • Draw a number line on the board, running from 0 to 1000 (you can also lay tape on the floor, or use a tile floor as a coordinate plane!).

    • We are going to write a function, called update-target, that will be responsible for changing the x-coordinate of the TARGET location.
      Note: In our game, there is hidden code that will randomly generate the y-coordinate for where the TARGET enters the screen. Our update-target function will take in that coordinate, but won’t change it. For this role play, it will likely make the most sense to work with a y-coordinate of 0.

    • Before we write the function, let’s act it out!

    • Select a student volunteer to be TARGET and pick a starting location for our TARGET, eg. (300, 0) .

    • For this roleplay, we will have our update-target function move our TARGET left across the x-axis by 50 (pixels) each time the function is called.

      • When the TARGET hears "update target" followed by their current location, they take a step in the negative direction, moving left across the x-axis by 50 (pixels).

      • Make TARGET move by calling out the function and starting location, eg. update-target(300, 0).

      • Make TARGET move several more times by calling out the function and new location, eg. update-target(250, 0), etc.

    • Ask students: How could we change our update-target function to move the TARGET across the classroom more quickly?

      • We could have the TARGET move by more pixels each time, for example by 100 instead of 50.

    • What did you notice about the movement of TARGET? What was changing?

      • Answers will vary: they were moving horizontally, their x-coordinates were changing, they were moving one step at a time, etc.

    • If we want to write another function called update-danger and have it move the DANGER 50 pixels to the right, how will the function work?

      • It will take in the x and y-coordinate and add 50 to x.

    Investigate

    • Sign in to code.pyret.org (CPO) and open your saved Game Starter Files, or make a new copy.

    • Examine the update-danger function. Identify the Contract, and interpret what the function is currently doing.

    • Complete the first word problem on Danger and Target Movement.

    • Transfer the code to your Game Starter File.

    When students click the "Run" button, the working update-danger function should automatically move the DANGER image across the screen!

    • Complete the second word problem on Danger and Target Movement.

    • With your partner, transfer the code to your Game Starter File.

    • Click "Run" to see DANGER and TARGET move across the screen independently!

    Extension Activities

    Once students have successfully gotten update-target and update-danger working, they can change the functions to make the characters move in whichever direction and whatever speed they want to make the game the most fun to play! They should be sure to modify their purpose statements and examples if they change their functions.

    Synthesize

    Connecting the code to the underlying math is important - especially if you want to customize your game!

    • What part of the function controls the character’s speed?

    • What part of the function controls the character’s direction?

    • If you wanted the characters to move in 2 dimensions (diagonally, for example), would anything have to change about the Domain? What about the Range?

    These materials were developed partly through support of the National Science Foundation, (awards 1042210, 1535276, 1648684, 1738598, 2031479, and 1501927). CCbadge Bootstrap by the Bootstrap Community is licensed under a Creative Commons 4.0 Unported License. This license does not grant permission to run training or professional development. Offering training or professional development with materials substantially derived from Bootstrap must be approved in writing by a Bootstrap Director. Permissions beyond the scope of this license, such as to run training, may be available by contacting contact@BootstrapWorld.org.