Introduction to Computer Science with Scratch and App Inventor

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User Controlled Sprites and Branching When you click the import button, a box will open that lets you navigate through the library of backgrounds. Pick one that you like and click OK to make it the new background on your stage. To go back to working on your script for your sprite, you just click on the sprite in the sprite list. Click here to go back to your sprite For both sprites and backgrounds, you aren’t limited to the options in the Scratch library. You can also draw your own sprites, modify existing sprites, or import drawing/photo files from your computer. We will see how to do this in later lessons. Up until now, all of our sprite’s actions have been controlled by move blocks. However, in a game, we’ll want the user to be able to move the sprite around using the keyboard. In order to be able to do this, we need to learn a new control block first: The if block implements a BRANCHING control structure. Branching lets us choose to do something, only if certain conditions are met. We do this all of the time in real life. For example, we might say if it is raining, take an umbrella outside. This means that when the condition “it is raining” is true, we should take an umbrella outside with us. We will use branching in programming in much the same way. mbrace Game Development Workbook Page 12
To use an if block to control the movement of the sprite, we first have to think about what conditions we want to test. Let’s use the standard arrow keys as our conditions. This means we want to test the following conditions: If the up arrow is pressed, we want the sprite to move up the stage (this is a positive change in the y value of the sprite’s location) If the down arrow is pressed, we want the sprite to move down the stage (this is a negative change in the y value of the sprite’s location) If the left arrow is pressed, we want the sprite to left on the stage (this is a negative change in the x value of the sprite’s location) If the right arrow is pressed, we want the sprite to right on the stage (this is a positive change in the x value of the sprite’s location) Let’s look at our if block again. Next to the word “if” you’ll see a diamond shaped opening. This is where the condition will go. The action to do if the condition is true goes inside the block. condition to check goes here action to do if condition is true goes here Where do we get the conditions? There are several different types of blocks that can go into the condition spot. All blocks that can go in a condition spot will be diamond-shaped, just like the opening in the if block. One place to get condition blocks is the sensing menu. Blocks on the sensing menu let us check for events like: Mouse events: when the user clicks the mouse (you can also get the location of the mouse arrow on the screen) Keyboard events: when the user pushes a button on the keyboard (here we are interested in capturing specific keys – the arrow keys – but you can capture any key you want) When two objects on the screen are touching each other We will use the sensing menu throughout our game, so it is useful to become familiar with the available blocks. mbrace Game Development Workbook Page 13
Page 1 and 2: Introduction to Computer Science wi
Page 3 and 4: LESSON 1: Getting Started with Scra
Page 5 and 6: I decided to pick a dinosaur. You c
Page 7 and 8: The direction that your sprite move
Page 9 and 10: Let’s add some yellow wait blocks
Page 11: Changing the Background on the Stag
Page 15 and 16: Costumes and Animation Now that you
Page 17 and 18: Other useful blocks are the say and
Page 19 and 20: ? Now we know how to tell when the
Page 21 and 22: Here is one script that works. To m
Page 23 and 24: After you create a variable, you wi
Page 25 and 26: Winning, Losing, and Game Play Our
Page 27 and 28: You might have noticed that when th
Page 29 and 30: Click the checkbox next to timer to
Page 31 and 32: Scratch Review Now you have built y
Page 33 and 34: App Inventor Interface The App Inve
Page 35 and 36: The first thing that we will do is
Page 37 and 38: To add the mole to our program, we
Page 39 and 40: Your Blocks Editor Screen should lo
Page 41 and 42: We know that our X and Y locations
Page 43 and 44: Our mole shows up in the emulator,
Page 45 and 46: The last thing we need is the value
Page 47 and 48: Team Project Worksheet We have lear

Introduction to Computer Science with Scratch and App Inventor

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