Project 3: Ants Vs. SomeBees

The bees are coming!
Create a better soldier
With inherit-ants.


In this project, you will create a tower defense game called Ants Vs. SomeBees. As the ant queen, you populate your colony with the bravest ants you can muster. Your ants must protect their queen from the evil bees that invade your territory. Irritate the bees enough by throwing leaves at them, and they will be vanquished. Fail to pester the airborne intruders adequately, and your queen will succumb to the bees' wrath. This game is inspired by PopCap Games' Plants Vs. Zombies ®.

This project combines functional and object-oriented programming paradigms, focusing on the material from Chapter 2.5 of Composing Programs. The project also involves understanding, extending, and testing a large program with many related parts.

This project includes several files, but all of your changes will be made to the first one. You can download all of the project code as a zip archive. The game logic of Ants Vs. SomeBees. A suite of tests for the project. Graphics for Ants Vs. SomeBees. General functions for displaying simple two-dimensional animations. Utility functions for CS 61A. Utility functions for grading.
img A directory of images used by the graphical version of the game.


This is a two-week project. You'll work in a team of two people, person A and person B. In each part, you will do some of the work separately and some together with your partner. For example, if a problem is marked A1, then it is a solo problem for person A. Both partners should read, think about, and understand the solution to all questions. Feel free to help each other on the solo questions. If you choose to work on the whole project alone, you must complete all questions yourself.

Start early! The amount of time it takes to complete a project (or any program) is unpredictable. Ask for help early and often -- the TAs and lab assistants are here to help. You are not alone!

The only file that you are required to edit is You do not need to modify any other files to complete the project.

Core Concepts

A game of Ants Vs. SomeBees consists of a series of turns. In each turn, new bees may enter the ant colony. Then, new ants are placed. Finally, all insects (ants, then bees) take individual actions: bees sting ants, and ants throw leaves at bees. The game ends either when a bee reaches the ant queen (you lose), or the entire bee flotilla has been vanquished (you win).

The Colony. The colony consists of several places that are chained together. The exit of each Place leads to another Place.

Placing Ants. There are two constraints that limit ant production. Placing an ant uses up some amount of the colony's food, a different amount for each type of ant. Also, only one ant can occupy each Place.

Bees. When it is time to act, a bee either moves to the exit of its current Place if no ant blocks its path, or stings an ant that blocks its path.

Ants. Each type of ant takes a different action and requires a different amount of food to place. The two most basic ant types are the HarvesterAnt, which adds one food to the colony during each turn, and the ThrowerAnt, which throws a leaf at a bee each turn.

The Code

Most concepts in the game have a corresponding class that encapsulates the logic for that concept. For instance, a Place in the colony holds insects and connects to other places. A Bee stings ants and advances through exits.

The game can be run in two modes: as a text-based game or using a graphical user interface (GUI). The game logic is the same in either case, but the GUI enforces a turn time limit that makes playing the game more exciting. The text-based interface is provided for debugging and development.

The files are separated according to these two modes. knows nothing of graphics or turn time limits. All graphical elements are specified in and It is possible to complete this project without ever reading the graphics files.

To start a text-based game, run


To start a graphical game, run


When you start the graphical version, a new window should appear:

In the starter implementation, you have unlimited food and your ants only throw leaves at bees in their current Place. Try playing a game anyway! You'll need to place a lot of ThrowerAnts (the second type) in order to keep the bees from reaching your queen.

The game has several options that you will use throughout the project, which you can view with --help.

python3 [|] [OPTIONS]
    Run the Ants vs. SomeBees project.

    -h, --help      Prints this help message
    -t, --ten       Start with ten food
    -f, --full      Loads a full layout and assault plan
    -w, --water     Loads a full layout with water
    -i, --insane    Loads a difficult assault plan

You have also been provided a testing file that runs a series of unit tests for the project. To test your project, you can run

python3 -v

This command runs all of the unit tests along with any doctests in The optional -v generates more verbose output. You can also run tests for individual questions:

python3 -q 2
python3 -q A5

If you would like to learn more about Python's built-in unit testing framework, read the documentation of the unittest module. Most problems have associated tests. Make sure that the tests for each problem pass before moving on.

Phase 1

Both Partners

Problem 1 (0 pts). Answer the following questions with your partner after you have read the entire file. If you cannot answer these questions, read the file again.

  1. Which method in which class runs a game? (the answer is not run, because run is not a method)!
  2. The Hive, a subclass of Place, is the starting location of the bees. Unlike most instances of Place, the Hive class does not have an exit. Explain how and when Bees leave the Hive.
  3. Explain the mechanism in the code by which the places in the colony are laid out. How do you modify the code to produce more places?
  4. What is the significance of an Insect's armor attribute? What happens when armor reaches 0?

Problem 2 (2 pts). Add food costs and implement harvesters. Currently, there is no cost for deploying any type of Ant, and so there is no challenge to the game. You'll notice that Ant starts out with a base food_cost of 0. Override this value in each of the subclasses listed below with the correct costs.

Class Food Armor

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Now there's no way to gather more food! To fix this issue, implement the HarvesterAnt class. A HarvesterAnt is a type of Ant that adds one food to the total as its action.

Try playing the game again. Once you have placed a HarvesterAnt, you should accumulate food each turn. Vanquishing the bees using the default game setup is now possible.

Problem 3 (1 pts). Add code to the Place constructor that tracks entrances. Right now, a Place keeps track only of its exit. We would like a Place to keep track of its entrance as well. A Place needs to track only one entrance.

However, simply passing an entrance to a Place constructor will be problematic; we will need to have both the exit and the entrance before we can create a Place! (It's a chicken or the egg problem.) To get around this problem, we will keep track of entrances in the following way instead. The Place constructor should specify that:

Person A: Water and Fire

Problem A4 (2 pts). Add water to the colony. Currently there are only two types of places, the Hive and a basic Place. To make things more interesting, we're going to create a new type of Place called Water.

Only an ant that is watersafe can be deployed to a Water place. In order to determine whether an Insect is watersafe, add a new attribute to the Insect class named watersafe that is False by default. Since bees can fly, make their watersafe attribute True, overriding the default.

Now, implement the add_insect method for Water. First call Place.add_insect to add the insect, regardless of whether it is watersafe. Then, if the insect is not watersafe, reduce the insect's armor to 0 by invoking reduce_armor. Do not copy and paste code. Try to use methods that have already been defined and make use of inheritance to reuse the functionality of the Place class.

Once you've finished this problem, play a game that includes water. To access the mixed_layout that includes water, add the --water option (or -w for short) when you start the game.

python3 --water

Problem A5 (3 pts). Implement the FireAnt. A FireAnt has a special reduce_armor method: when the FireAnt's armor reaches zero or lower, it will reduce the armor of all Bees in the same Place as the FireAnt by its damage attribute (defaults to 3).

Class Food Armor

4 1

Hint: If you iterate over a list, but change the contents of that list at the same time, you may not see all the elements. As the Python tutorial suggests, "If you need to modify the list you are iterating over, you must iterate over a copy." Remember that damaging a bee may cause it to be removed from its place.

Once you've finished implementing the FireAnt, give it a class attribute implemented with the value True. This attribute tells the game that you've added a new type of Ant.

After implementing FireAnt, be sure to test your program by playing a game or two! A FireAnt should destroy any co-located Bees when it dies. To start a game with ten food, use --ten.

Person B: Extended Range

Problem B4 (2 pts). Implement the nearest_bee method for the ThrowerAnt class. In order for a ThrowerAnt to attack, it must know which bee it should hit. The provided implementation will only hit bees in the same Place. Your job is to fix it so that a ThrowerAnt will throw_at the nearest bee in front of it that is not still in the Hive.

The nearest_bee method returns a random Bee from the nearest place that contains bees. Places are inspected in order by following their entrance attributes.

After implementing nearest_bee, a ThrowerAnt should be able to throw_at a Bee in front of it that is not still in the Hive. Make sure that your ants do the right thing! To start a game with ten food, use --ten.

Problem B5 (3 pts). Now that the ThrowerAnt has been completed, implement two subclasses of ThrowerAnt.

Neither of these specialized throwers can throw_at a Bee that is exactly 3 Places away. Placing a single one of these (and no other ants) should never win a default game.

Class Food Armor

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To implement these behaviors, modify the nearest_bee method to reference min_range and max_range attributes, and only return a bee that is in range.

For the base class, ThrowerAnt, set min_range to 0 and max_range to 10. Then, implement the subclasses LongThrower and ShortThrower with appropriately constrained ranges and correct food costs.

Set the implemented class attribute of LongThrower and ShortThrower to True.

Try playing a game with your newly implemented ants. Be sure that they do what you expect them to! You can try running with the --full option to go up against a full swarm of bees in a multi-tunnel layout, and add --insane if you want a real challenge! If the bees are too numerous to vanquish, you might need to create some new ants in Phase 2.

Phase 2

Person A: Seen and Unseen

Problem A6 (1 pts). We are going to add some protection to our glorious AntColony by implementing the WallAnt, which is an ant that does nothing each turn (already the default action of the Ant class). A WallAnt is useful because it has a large armor value.

Class Food Armor

4 4

Problem A7 (3 pts). Implement the NinjaAnt, which damages all Bees that pass by, but is never seen.

Class Food Armor

6 1

A NinjaAnt is not able to be attacked by a Bee because it is hidden, nor does it block the path of a Bee that flies by. To implement this behavior, first modify the Ant class to include a new class attribute blocks_path that is True by default. Set the value of blocks_path to False in the NinjaAnt class.

Second, modify the Bee's method blocked to return False if either there is no Ant in the Bee's place or if there is an Ant, but its blocks_path attribute is False. Now Bees will just fly past NinjaAnts.

Finally, we want to make the NinjaAnt damage all Bee's that fly past. Implement the action method in NinjaAnt to reduce the armor of all Bees in the same place as the NinjaAnt by 1, overriding the default action method inherited from Ant. Make sure that you override and use the inherited damage variable.

For a challenge, try to win a default game using only HarversterAnt and NinjaAnt.

Person B: By Land and Sea

Problem B6 (1 pts). Currently there are no ants that can be placed on Water. Implement the ScubaThrower, which is a subclass of ThrowerAnt that is more costly and watersafe, but otherwise identical to its base class.

Class Food Armor

5 1

Placing a ScubaAnt in Water should not cause it to die.

Problem B7 (3 pts). We will now implement the new offensive unit called the HungryAnt, which will eat a random Bee from its place, instantly killing the Bee. After eating a Bee, it must spend 3 turns digesting before eating again.

Class Food Armor

4 1

To implement, give HungryAnt a time_to_digest class attribute that holds the number of turns that it takes all HungryAnts to digest (default to 3). Also, give each HungryAnt an instance attribute digesting that counts the number of turns it has left to digest (default is 0, since it hasn't eaten anything at the beginning).

Now we implement the action method of the HungryAnt to check if it's digesting; if so, decrement its digesting counter. Otherwise, eat a random Bee in its place (killing the Bee and restarting the digesting timer).

Both Partners

Problem 8 (5 pts). Implement the BodyguardAnt. Right now, our ants are quite frail. We'd like to provide a way to help them last longer against the onslaught of the bees. Enter the BodyguardAnt.

Class Food Armor

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A BodyguardAnt differs from a normal Ant because it can occupy the same Place as another ant. When a BodyguardAnt is added to the same Place as another ant, it shields the other ant and protects it from damage. Attacks should damage the BodyguardAnt first and only hurt the protected ant after the BodyguardAnt has perished.

A BodyguardAnt has an instance attribute ant that stores the ant contained within the bodyguard. It should start off as None, indicating that no ant is currently being protected. Give BodyguardAnt a contain_ant method that takes an Ant argument and sets the ant instance attribute to that argument.

Now, change your program so that a BodyguardAnt and another Ant can simultaneously occupy the same Place:

  1. Add an Ant.container class attribute that indicates whether an ant can contain another. For all Ants except BodyguardAnt, container should be False. The BodyguardAnt.container attribute should be True.
  2. We also need to give Ants a new method, can_contain, that takes an other ant as an argument and returns True if and only if:
    1. This ant is a container.
    2. This ant does not already contain another ant.
    3. The other ant is not a container.
  3. Right now, if we attempt to put a second ant in a Place, the add_insect method of the Place class will immediately cause an error. Change add_insect so that the Place contains the container ant and the container ant contains the other ant:

Almost done! Just a few more things to do.

  1. If a BodyguardAnt containing another ant is removed, then the ant it is containing should be placed where the BodyguardAnt used to be. Update the remove_insect method in the Place class accordingly.
  2. The last step is to make sure that ants that are contained by BodyguardAnts still perform their action. Override the action method for BodyguardAnt accordingly.

Problem 9 (5 pts). Implement the QueenAnt. The queen is a waterproof ScubaThrower that inspires her fellow ants through her bravery. Whenever the queen throws a leaf, she also doubles the damage of all other ants in the same tunnel with her, including any ants protected by a bodyguard. Once any ant's damage has doubled, it cannot be doubled again.
Class Food Armor

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However, with great power comes great responsibility. The Queen is governed by three special rules:

  1. If a bee ever enters the place occupied by the queen, then the bees immediately win the game. The game ends even if the queen is protected by a bodyguard. The bees also win if any bee reaches the end of a tunnel where the queen normally would reside.

    In AntColony.simulate, the bees win the game whenever len(self.queen.bees) > 0, where self is the ant colony. Normally, the queen attribute of an AntColony is an instance of a Place. As part of the action of a QueenAnt, the colony.queen should be replaced by a new object, a QueenPlace. A QueenPlace has a bees property method that evaluates to the list of all bees that are either in the original colony.queen location or the place of the QueenAnt.

    You should not have to change the implementation of AntColony.simulate or manipulate the location of bees in any special way. You may assume that a colony.queen attribute will be used for only one purpose: to check whether len(self.queen.bees) > 0. Thus, a QueenPlace instance does not need to support other Place methods, such as add_insect.

  2. There can be only one true queen. Any queen beyond the first one is an impostor and should die immediately (its armor reduced to 0) upon taking its first action, without doubling any ant's damage or throwing anything. Impostor queens should not affect the colony's queen attribute. You can detect impostor queens by counting the number of times that an instance of a QueenAnt has been constructed, using a class attribute. Any QueenAnt beyond the first one created is an impostor. You should not have to search through the colony places to find other queens.

  3. The true (first) queen cannot be removed. Attempts to remove the queen should have no effect (but should not cause an error). You will need to modify the remove_insect method of Place to enforce this condition.

Some suggestions:

Extra Credit (2 pts). Implement two final thrower ants that do no damage, but instead replace the action method of a Bee instance that they throw_at with a new method that alters the Bee's behavior for some duration.

We will be implementing two new ants that subclass ThrowerAnt.

Class Food Armor

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In order to complete the implementations of these two ants, you will need to set their class attributes appropriately and implement the following three functions:

Make sure to test your code! Your code should be able to apply multiple effects on a target (each new effect applies on top of whatever action method the bee already has at that point, and the target returns to the previous action when the new one runs out).

You are now done with the project! If you weren't able to vanquish the bees' insane-mode assault plan before, do your new ants help? Add some water or design your own layout to keep things interesting.

Acknowledgments: Tom Magrino and Eric Tzeng developed this project with John DeNero. Jessica Wan contributed the artwork. Joy Jeng and Mark Miyashita invented the queen ant. Many others have contributed to the project as well!