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Barb Ericson

Georgia Institute of Technology

June 2008

Creating a Simple Game in Alice

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Objectives

• Show how to create a simple game in Alice– Creating methods in Alice– Creating a field or property of an object– Creating a variable– Using a while loop– Creating a Boolean function– Creating a comment

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Things to Consider

• All objects in an Alice movie or game must be created before the game starts– you can make them invisible to start

• click on properties and set the opacity to 0

– you can also hide objects by moving them under the ground

• move down some amount

• You can update a field (property) in an object to track if it has been clicked on

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Click the Zombie Game• While the user hasn't won hide

the zombie and after some random amount of time between 1-3 seconds have it pop up in a random place.

• If the user clicks on the zombie increment the number of hits and when it reaches 5 let the user know s/he won

• If the user doesn't click on the zombie within 1 second hide it again

• Add instructions at the beginning to let the user know how to play– and then make them invisible

after some amount of time

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Set-up the World

• Click on File -> New World

• Select the Template tab

• Click on the grass world– click on open

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Add Objects to the World

• Click the add objects button at the bottom of the scene

• Scroll to the City category and click on City

• Add some Buildings by dragging out some building clusters

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Add the Zombie

• Click on Local Gallery to get back to the list of categories

• Open the People category

• Scroll over to Zombie and add one to the world

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Hide the Zombie

• Create a method to hide the zombie– Click on zombie in the

object tree– Click on methods in

the details window– Click the create new

method button– name the method hide

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The hide method

• Click on propertiesin the detail window

• Drag out opacity = 1 (100%)

• Put it in the hide method

• Change the opacity to 0 (0%)

• Click on methods• Pull out zombie move

down 2 meters

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Create the pop up method

• Click on methods• Click the create new

method button• name the method

popUp– move the zombie

randomly– move the zombie up

above the ground– make the zombie

visible

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Move the zombie randomly

• Start by dragging out zombie move tiles– one for each of left, right,

forward, and backward

• Click on world in the object tree to select it

• Click on functions in the details window

• Drag out random number and drop it on the 1 meter– select 0 for min and 2 for

the maximum

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Add a comment

• You can add a comment to explain what you are doing in English

• Drag a // tile from the bottom of the method editing window to where you wish to place the comment– Click on the down arrow– Select other– Type in the comment

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Showing the zombie

• Click on zombie in the object tree to select it

• Click on methods in the details window

• Drag out a zombie move tile– select up 2 meters

• Click on properties in the details window

• Drag out opacity = 0– change to 1 (100%)

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Adding a property (field)

• We need to store the number of hits on this zombie

• Click on the properties tab

• Click the create new variable button

• name the variable numHits– set the value to 0

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Increment the number of hits

• If the user clicks on the zombie we want to add 1 to the number of hits so far

• Create a method that does this– It should be a new zombie method

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Respond to mouse click on zombie

• In the events window click the create new event button– select When the

mouse is clicked on something

• Change the anything to the zombie (the entire zombie)

• Change the nothing to zombie incrementHits

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Method to run the game

• Click on world in the object tree

• Select methods• Pull up a while tile

from the bottom of the editor window– select true

• Click on functions– drag out a < b and

drop it on true• select 1 and 1

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While number of hits < 5

• Click on zombie in the object tree

• Click on properties– drag out numHits = 0

and drop on the first 1

• Change the second 1 to 5– click on other and

enter 5

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Hide and wait a random amount of time

• Click on methods• Drag out hide• Drag up a wait tile

from the bottom of the editor window– select 1 second

• Click on world in the object tree– click on functions– drag out random

number and drop on the 1 second

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pop up and wait for 1 second

• Drag out a zombie popUp

• Drag up a wait tile and select 1 second

• Try it out!– What happens after

you click on the zombie 5 times?

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Tell the user s/he won

• Add some 3D text that tells the user she or he won– Click on File and then on

Add 3D Text– Type in the text

• you can change the font

• Place it where you want it to appear– Click on add objects to get

to the mouse controls– Click on done when done

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Make the text invisible to start

• Click on the text in the object tree

• Click on properties– Modify opacity to 0

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When the user wins show the text

• Drag out opacity = 0 to the method– change to 1 (100%)

• Play the game!

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Speeding things up

• All animation takes 1 second by default– you can change this

using the more…

• Make the zombie move up or down and become visible and invisible at the same time– use a do together from

the bottom of the editor window

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Add instructions

• Create 3D text that tells the user what to do in the game

• When the game starts wait for 1 second– then make the text

invisible• can set isShowing to

false

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Show the number of hits

• Create 3D text that says Hits and one that says 0

• Click on the 0 in the object tree– Click on properties– Drag out text = 0

• select default string

• Use the mouse controls to position the text– Click on Add Objects to

see the mouse controls• when done click on done

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World incrementHits method

• Add an incrementHits method to the world– call the zombie

incrementHits method– click on 0 then properties

• drag out text = 0– select default string

• replace the default string with the what as string function in the world to convert the number to a string

• choose expressions and pick zombie numHits as what to convert

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Change when mouse clicked

• Modify then when mouse is clicked on the zombie to call the world's incrementHits method

• Try it!

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Other Ideas• Have the zombie play a sound when hit

– modify zombie incrementHits method– use play sound in methods

• you can also record your own sounds– click on properties for the zombie– click on the + next to Sounds– and record a sound and name it

• Count the number of times the zombie has appeared• Add a way to lose

– maybe it will only run till it appears 10 times– maybe add a timer and a time limit– maybe add other objects that if you click on these you lose

• Make the amount of time you give the user to click on the zombie a random amount from 0.5 to 1 second

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Summary

• Alice can be used to create simple 3D games

• Concepts covered– creating methods– creating a property (field)– creating a variable– using a while loop– creating a comment