CS 1102 (A12) Homework 2: The Fire Fighter Game

Assignment Goals

• To make sure you can write programs using combinations of lists and structures.
• To practice using the design recipe to organize a nontrivial program.

This homework continues using the graphics framework introduced in Lab 1.

Remember to follow the Expectations on Homework when preparing your solutions, including the academic honesty policy.

The Assignment

Your job is to write a simple interactive game in which the player drops water from a plane onto fires on the ground; the goal of the game is to put out all of the fires by dropping enough water on them. A sample appears to the right. The plane flies continuously back and forth across the screen (i.e., the plane is always moving, regardless of what the player does). The player can change the direction of the plane by pressing the left and right arrow keys. The player can also drop water from the plane by pressing the down arrow key. Each fire has an intensity: when a drop of water hits a fire, the intensity decreases. As a fire burns without water hitting it, its intensity increases. A fire is extinguished when its intensity reaches zero. You will build this game using the same image.ss and universe.ss teachpacks used in Lab 1. If you need more documentation, see Worlds and the Universe. Work in the "Beginning Student with List Abbreviations" language level. (See drop-down menu in lower left corner of DrRacket window.)

• A data definition for a "world", which is a single data structure containing all of the logical information that makes up the current configuration of the game (including the plane, fires, water drops and their component information).

  Do not assume the same number of fires for every playing of the game. You should be able to change the number of fires simply by changing the definition of INITWORLD (see below). You do not, however, need to write code to automatically generate a random number or placement of fires for each game play (as this will make writing test cases difficult).

• Include all data definitions needed to write your overall world data definition. Function templates are required for all data definitions.

• A function draw-world that consumes a world and produces a graphical scene of that world, using place-image and empty-scene as you did in lab. (Hint: Notice that the place-image function produces a scene, so you can nest calls to place-image to put multiple objects into a single scene.)

• A function update-world that consumes a world and produces a world reflecting what happens when no key is pressed (i.e., the plane continues to move, the water continues to fall, etc.).

• A function process-keys that consumes a world and a key-event (symbol) and produces a new world with changes based which key has been pressed.

Once you have these functions, you will run your game using these built-in functions (as you did in lab):

(big-bang INITWORLD
          (on-draw draw-world)
          (on-tick update-world)
          (on-key process-keys))

You must decide what other functions to implement as part of writing the required functions listed above. However, we expect you to follow the design-recipe strategy used in class in which one function uses one template to operate on one data definition. You may bend this rule for posn's nested within other structures (i.e., you don't need a separate function just to process the posn), but not for other data types you define. Also, if a function consumes two defined data types, pass one one argument directly to a helper function that uses that type's template to operate on it. If you don't follow this design recipe, this assignment will take you far longer than necessary. You'll also lose substantial points in the grading.

Strategy

If you and your partner prefer to work separately, work out and agree on the data definitions first, then proceed to work on the rest of the code (together or independently).

Implement the game in stages, not all at once. Start with a simple version that lets the user change the direction of the plane's movement, but has no fires or water. Once you have that working, add the water drops and get them to fall. Once that is working, add the fires. Get the fires to decrease in intensity when water hits them, then get them to increase in intensity when no water falls on them.

You will get more credit for a fully-working solution to part of the game than for a non-working solution to the whole game. You should have the game working at least through water drops falling for a passing grade on this assignment.

Hints and FAQs

• You will be graded primarily on the structure of your code, not on efficiency. Don't worry about efficiency. Your computations to check whether a water drop has hit a fire need to be reasonable, but do not need to be exact (i.e., don't waste time on getting these expressions correct down to the pixel). If the resulting game play looks plausible, we won't care about the precise formula you used.

• You may simply specify a stop-when (see lab) function to stop the game when all fires are extinguished. You do not need to add fancy screen graphics with the result of the game; you will not get extra points for doing so (though you are welcome to do this if you want).

• You may use whatever images you wish for the pieces of the game (the ones we used are below; feel free to use them or plain circles and rectangles if you prefer). We used the circle function provided in the teachpacks to draw the water drops, e.g.,

  (circle 5 "solid" "blue")

  and the different sized fire images for different ranges of intensity of fires.

• You do not need to reverse the image of the plane when it reverses direction or do anything fancy with the graphics. No extra points for fancy graphics work!

• You do not need test cases for functions that return scenes, but you do need test cases for all other functions.

• Remove extinguished fires from the world: certain aspects of the game will be much easier to program if you do this.

• Increase the intensity of the fire at a much lower rate than you decrease it (or the game becomes unplayable). Our prototype increased intensity at 1/100 the rate of lowering it, for example. You will want to use numbers with decimal points, rather than just integers for this.

Our Images

What to Turn In

Grade your own homework according to General Grading Guidelines before you hand it in!

Turn in a single file hwk2.rkt containing all code and documentation for this assignment. Make sure that both students' names are in a comment at the top of the file.