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StarLogoTNG 101

StarLogoTNG 101. Treasure Hunt Game Unit Lesson 9: Variables. Today’s Agenda. Review Mini-lesson on variables and new blocks Implement new game features Wrap-up. Review.

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StarLogoTNG 101

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  1. StarLogoTNG 101 Treasure Hunt Game Unit Lesson 9: Variables

  2. Today’s Agenda • Review • Mini-lesson on variables and new blocks • Implement new game features • Wrap-up

  3. Review • Whenever a moving enemy agent collides with a hazard, program the enemy to “hatch” a half size version of itself and have the child enemy head in a different direction from the parent. The hazard dies. • Whenever the moving enemy collides with a treasure, if the moving enemy is smaller than 1, it increases its size back to 1. The treasure dies. • Whenever the moving enemy collides with itself, program the enemy to “hatch” a new treasure. • Challenge: How can you use “random” so that the enemy only has a 50% chance of hatching a new treasure?

  4. Variables • What is a variable? (hint: what are some examples from math or science classes?) • A variable in programming is like a container that holds a value that can change. • The value can be a number, a boolean (true or false), or a string (characters like a word or phrase). 25 8 False True Hello Bye

  5. Variables • You’ve already used some variables such as score, xcor, and color. What are some other examples of already defined variables in StarLogo TNG? • Look in the Traits drawer. What type of variables are pen down?, pen up? and alive? How can you tell?

  6. Agent monitor window • If you click once on any agent in Spaceland, you bring up its monitor. Here you’ll see the current values of its already defined variables. • You can even change the values and immediately see the effect on that particular agent.

  7. Variables • You define (or create a container for) a variable using the blocks in the Variables drawer. • There are two kinds of variables: agent and shared. • If you define a shared variable, there is only one variable container for the whole game. • If you define an agent variable, every agent of a certain breed gets its own variable container.

  8. Shared vs. Agent • Shared variable • Agent Variable

  9. Variables: Practice 1 Classify each of the following variables as agent or shared: • Size • Xcor • Score • Breed

  10. Variables: Practice 2 How would you define variables for each of these purposes: • The number of treasures left in the game • The energy content of each bullet. • The number of “lives” that the player has • The number of bonus “speed boosts” that can be triggered by the player

  11. Setting the value of a variable • Set variable block found in My Blocks palette. • Shared variable only: Slider – can be adjusted by the user in the Runtime window.

  12. Setting the value of a variable • Typically, you want to set the starting value of each variable in the Setup block as a part of resetting the game. For agent variables, you can set the starting value as part of the Create-Do block or the Hatch-Do block. • When the game is running, you’ll change the variable as needed by using the set variable block with an expression or constant.

  13. Getting the value of a variable • You want to “get” the value of a variable as part of changing its value (see previous set variable example) or to compare it to another number as a way of making a decision. • To get the variable, go to the My Blocks palette and look inside the drawer of the canvas section where you declared the variable.

  14. Getting the value of a variable • So, in our example with the mana variable, the player collects “mana” and then can use mana to do special things like let the player move faster for a certain period of time.

  15. Monitor • Use the monitor block in the Setup and Run drawer to show the value of shared variables.

  16. Guided Programming • Open the current version of your “treasure game your initials.sltng” • Save next version • Define an agent number variable called “energy” in the thrown projectile section of the canvas. • When hatching the projectiles, set energy to 100. • In the Run (forever) block, in the projectile’s section, decrease the energy variable by 1. When the energy gets down to zero, the projectile dies.

  17. Guided Programming • Note the addition of the energy variable in the agent monitor window of a projectile agent.

  18. Brainstorm uses for Variables What other uses for variables can you think of for your game? Here are some ideas: • The number of treasures left in the game • The energy content of each bullet. • The number of “lives” that the player has • The number of bonus “speed boosts” that can be triggered by the player • Timer to track the “life” of certain agents or events

  19. Programming Activity • Implement a new game element that uses at least one variable. • Decide on the game element, consider which type of variable is most appropriate, and then follow the steps below. • Three basic steps to using a variable: • Define the variable • Initialize the variable (setup, create, hatch) • Use the variable (change it, compare it, etc.)

  20. Wrap Up • Describe your new game feature that uses one or more variables. • What worked? What didn’t work? • What challenges did you have? • What was fun? • What questions do you have? • What new game ideas do you have?

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