NotPeggle

A simple Peggle clone done as a school project.

Dev Guide

Architecture

Overall, NotPeggle can be split into three components, LevelDesigner, Game and Services. As the name suggests, LevelDesigner is responsible for the level editor and its subcomponents, Game is responsible for the actual game and its engines and Services is responsible for utility static methods that the other two depend on.

Level Designer

LevelDesigner follows the MVC pattern, comprising mainly a model component and a view(-controller) component.

View

The view component comprises of controllers and view objects.

The LevelViewController is responsible for:

• initialising the controls on the screen such as the buttons and text field,
• updating the Model based on input from other view and
• creating, changing or removing PegView, BlockView UI objects based on those updates.

The SaveTableViewController is responsible for:

• displaying all saved levels from the application document directory
• removing unneeded saves (done through Storage) based on user input
• relaying a chosen save file back to the LevelViewController to be loaded.

PegView is the view representation of a Peg. and BlockView is the counterpart for Block.

Model

The model component comprises (from top-level to bottom) the Model struct, the Peg and Block struct, and the Point struct. Model is composed of all Peg and Block instances in the board at any point in time, and has operations for querying and inserting/deleting objects.

LevelObject is a protocol that defines collision detection for objects in the Model, and Peg and Block serves as its conforming structs.

A Peg is represented simply as a circle with a Point indicating its center radius, and color.

A Block is represented as a rectangle with a Point as its center, its width and height and its angle offset.

A Point represents a pair of x, y-coordinates in a 2D plane.

Logic Flow in LevelDesigner

To examine the relationship between components in LevelDesigner, we will examine what happens when a user selects the blue peg button and taps on the board to add a new blue peg to the level.

The following sequence diagram shows the processes involved in adding a new blue peg.

1. Upon receiving a tap event on the blue PegModeButton, the view controller is set to add blue pegs to the board.
2. Upon receiving another tap event on the board, it creates a new blue Peg at the location of the tap
3. It adds the new peg to the model.
4. It then loads data from the model to the view, which includes displaying a new blue peg on the screen.

The following object diagrams show the state of the programme during the execution of said processes.

1. In the initial state, let's have a board that already has 2 pegs present, both of which are displayed (represented by the PegView objects).
2. The events of the sequence event takes place and newPeg is created and added to the model.
3. The view controller detects that the change and creates the newView object to represent the extra peg and display it.

Game

Game is structured in an MVC fashion, with GameEngine serving as the model controlling the state of objects within the game, and the GameViewController updating the model and then updating the view based on observed changes to the model.

View

The View component comprises both the view objects and the GameViewController. GameViewController is responsible for:

• Initialising the engine from existing level data
• Running the game loop
• Conveying user input to the engine
• Rendering view objects in each loop to match the data in the engine
• Popping itself off the view stack when the user leaves the game

The view objects comprise the GamePegView, GameBlockView and CannonBallView, which are, as their names suggests, the game representation of the pegs, blocks and cannon ball as displayed in the UI.

Physics

Before we introduce the engine, one must understand the physics engine it is built upon. The Physics component comprises the PhysicsWorld and PhysicsObject. The PhysicsWorld represents the physics engine housing all PhysicsObject instances. It primarily updates the positions of every object, after which it resolves any collisions between them.

PhysicsObject represents an abstract 2D object that is affected by physics and has operations for updating position and velocity and declarations for collision handling.

It is concretely subclassed by PhysicsBlock and PhysicsBall, which represents an oriented-bounding box and circle in 2D space.

The physics component also includes several convenient blueprints for generic objects such as an immovable circle (StationaryObject or a bouncy ball affected by gravity (GravBouncingBall).

Engine

The Engine component comprises GameEngine, PowerUpManager and their respective game objects and power-ups.

GameEngine handles game logic, it houses the pegs and cannon ball and updates their position through the physics engine. It is also responsible for controlling the launch of the cannon.

PowerUpManager is a component under GameEngine that handles the selection and activation of power-ups when triggered by a green peg being hit.

GamePeg, GameBlock and CannonBall both subclass the PhysicsObject so they may be stored in the physics engine and updated by it.

Logic Flow in Game

To illustrate the relationship between Game components in action, we shall examine how the game updates the position of the cannon ball in its flight in the below sequence diagramme.

As we can see, at each step, the display calls GameViewController.refresh(). This cues the view controller to call GameEngine to reload its data. The engine then calls on PhysicsWorld to update the states of all objects within it, which includes the cannon ball location. After the cannon ball's location has been updated, the engine then tells the observing view controller to update its sprites, during which the latter updates the cannon ball position and other sprites on the screen for the user to see.

Services

Services houses utility structs such as:

• Storage - handles persistence
• ModelViewConverter - provides functions for translating UI elements into model counterparts and vice versa
• ModelGameConverter - provides functions for translating level designer structs into its game engine counterparts and vice versa
• Constants - information shared by both model and UI.

Patterns used

NotPeggle makes heavy use of the MVC pattern and observer/delegate patterns for relaying information between objects.

There is also heavy use of the adapter pattern to minimise dependency between components such as the converter structs found in Services.

Rules of the Game

Please write the rules of your game here. This section should include the following sub-sections. You can keep the heading format here, and you can add more headings to explain the rules of your game in a structured manner. Alternatively, you can rewrite this section in your own style. You may also write this section in a new file entirely, if you wish.

Cannon Direction

Please explain how the player moves the cannon.

To use the cannon, the player must first aim the cannon, then fire a round.

Simply drag your finger over the playing area (with the beach background) to your intended target. The cannon will automatically point directly at that location. Be warned! The cannon will not account for gravity when turning, that is on you to figure out.

When you are ready to fire, hit the button that says "LAUNCH". The launch button also shows the number of shots you have left. Firing the cannon causes that number to decrement by 1, and the cannon immediately launches a ball towards wherever you aimed at. Aim carefully before you do, because if you run out of shots too soon you lose!

The launch button is disabled when your previously-fired round has not yet left the screen, or when the game has already ended. However, you can continue to aim the cannon wherever you like in preparation for the next shot.

Win and Lose Conditions

Please explain how the player wins/loses the game.

When you start a level, the game calculates the minimum score you must obtain in order to win. This score is calculated by the number of pegs you have multiplied by 100. The player must aim to hit this goal by hitting pegs every turn. The scoring system is as follows:

1. Blue - 100 points
2. Green - 100 points
3. Orange - 200 points.

You win so long you hit the minimum score within your allocated shots.

If you run out of shots before you hit the minimum score, you lose!

And don't try to start a game without any pegs, if none are found the game will leave you a nasty message.

If your ball is stuck, don't worry, after around 10 seconds the game should remove the ball and any pegs the ball had hit up to the point of removal, and will be taken as if the ball had fallen out of the area.

Power-Ups

Green pegs are worth as much as blue pegs in points, but they activate power-ups when hit. The two power-ups are Space Blast and Spooky Ball (or rather their clones). Hitting green pegs cause them to activate in order with Space Blast first, then Spooky Ball, then Space Blast again, so on so forth. Power-ups can be activated multiple times in one round so long the ball continuously hits green pegs.

Space Blast

Space Blast causes pegs in the vicinity of the green peg to be highlighted instantly, effectively allowing you to score lots of points with a single hit.

Spooky Ball

Spooky Ball gives the ball an extra life, respawning it back at the top when after it falls through the ground. Its effect does not stack, i.e. activating Spooky Ball multiple times will not grant the cannon ball anymore respawns while until it has fallen out of the game area and has respawned.

That said, be careful not to get stuck! Since it would be meaningless to drop the ball vertically back down to where it was stuck originally, the ball will be removed, regardless of whether you had the perk active.

Level Designer Additional Features

Peg Rotation

Please explain how the player rotates the pegs.

There is a grey button labelled "ROTATE OR RESIZE" next to the erase button. When you tap on it, it will be highlighted. That is your cue that you can now freely rotate pegs and blocks as you wish.

Simply tap on the object you have in mind and a pop up will appear. The labels above the sliders are self-explanatory (I hope). Simply drag the slider labelled "Rotation" until you are satisfied. The slider supports full 360 degrees clockwise movement. While rotation is supported for pegs, you obviously won't see a problem since pegs are completely round and uniform.

Do note that for blocks, if the rotating block starts to clash with the borders or another object, the slider will not allow you to continue. Move the block out of the way if you want to continue.

When you are done, simply tap anywhere that is not a peg or a button to close the menu.

If you tap on another button (e.g. to add blue pegs) while the rotation menu is still open, do not fret, you can still make last minute adjustments to the current object before tapping out.

Peg Resizing

Please explain how the player resizes the pegs.

Similar to rotations, tapping on a peg with the "ROTATE OR RESIZE" button active will bring up the menu with labelled sliders. For pegs, you can adjust their diameter, and for blocks you can adjust their width and height.

Resizing is done about the center, i.e. the object grows outwards along its local axis.

Similarly to rotating objects, the slider will not progress if there is an obstacle in the way of your growing object. Move it to a place clear of obstacles to continue.

Likewise, you can still make last minute adjustments when you tap on a button while the resizing menu is open.

Bells and Whistles

Please write all of the additional features that you have implemented so that your grader can award you credit.

None lol

Tests

If you decide to write how you are going to do your tests instead of writing actual tests, please write in this section. If you decide to write all of your tests in code, please delete this section.

Refer to the testing plan in PS2 and PS3 for rough overview of past tests.

As for new additions, we will focus mainly on collision detection between rotated rectangles, and between circles and rotated rectangles. While needed in both the level designer and physics engine, only the level designer Model implementation has unit tests due to the minimal differences and time constraints.

Due to trigonometry and floating point precision, it is not easy to come up with extensive unit tests, hence this is backed up with manual testing.

For collision resolution, due to it being a lot more complicated to predict than detection for rectangles for the reasons above, this is done entirely manually.

Items to manually test:

1. [Level Designer] Placing blocks
   1. Adapt PS2 test cases for testing placement validity, delete and drag functionality for blocks
2. [Level Designer] Collision detection for blocks
   1. Requirements: blocks in assorted orientation (e.g. axis-aligned, pointing up or down), pegs
   2. For any block, a peg should not be able to intersect any point
   3. For any block, it should not be able to be dragged into intersection with another block
   4. For any block, it should not be able to be dragged into intersection with another peg
   5. For any block, it should not be able to be dragged into crossing the boundaries of the game area
3. [Level Designer] Rotation and resizing of pegs and blocks
   1. Adapt PS2 test cases for testing UIButton selection state for the rotation/resize button
   2. Resizing pegs:
      1. Tapping a peg with the button enabled should create a popup with only a "Size"and "Rotation" slider.
      2. Sliding the size slider for a peg should expand it or contract it until it reaches the end.
      3. If there are other objects or boundaries in the way of the peg, the slider should stop moving and the peg stop growing.
      4. Resized peg should have collision detection that reflects the changed shape (i.e. objects should not be able to clip with an enlarged peg or be blocked by a shrunk unobstructive peg)
   3. Rotating pegs:
      1. Slider should move as expected with no visible change to the peg view.
   4. Resizing block:
      1. Tapping a block with the button enabled should create a popup with a "Height", "Width"and "Rotation" slider. If the block was directly created, the width slider should be away from the minimum position.
      2. Similar behavior in 3.2.2 and 3.2.4 should be observed when tinkering with block sizes.
   5. Rotating block:
      1. Resizing a block after rotating should preserve its shape (i.e. its should not be distorted or grow towards the wrong axes)
      2. Rotated block should meet the collision requirements in part 2.
   6. Testing popup closure:
      1. Requirements: rotate/resize button selected, popup open after tapping an object
      2. Tapping anywhere that is not a button (text field included) and object should close the popup
      3. Tapping on another object should close the popup and reopen one that reflects the new object's state
      4. Popup should remain open when selecting a button such as the blue button
         1. Even with another mode selected the object can still be manipulated in the popup
         2. Tapping outside closes the popup and reverts to expected behavior for said mode in 3.6.4.1
      5. Resetting, saving or selecting a load save should close the popup.
4. [Level Designer] Preloaded saves
   1. Clicking load button should show at least 3 saves, the top being prefixed with "[DEFAULT]"
   2. Selecting, adding objects and re-saving one should create a new entry instead of overwriting.
   3. Adding the "[DEFAULT]" prefix to the save created in 4.2. should create a new save with the same name instead of overwriting.
   4. The first three saves in the list should not be able to be deleted.
5. [Game] Transfer of objects from Level Designer to Game
   1. Adapt PS3 test cases to ensure blocks and pegs created (and manipulated like in part 3) are correctly shown on the screen
6. [Game] Win/Lose
   1. Starting a game with no pegs on the screen gives you a popup with a hostile message
      1. Launch button should be greyed out
   2. Scoring:
      1. The denominator of the score should be equal to number of pegs times 100.
      2. Hitting a peg multiple times should not cause the score to increase after it had already done so
   3. Winning:
      1. When you hit the score limit the game should congratulate you with a popup
      2. Launch button is greyed out so you can only go back to the level designer
      3. Outstanding pegs are untouched until you leave the game
   4. Losing:
      1. When the ball disappears and there are no more shots left (launch button indicator) game should show you a hostile message if the score limit is not reached.
7. [Game] Collision resolution between cannon ball and blocks
   1. Requirements: all sorts of blocks of different orientation, at least one peg to allow the game to start
   2. Ball should bounce in a believable fashion.
8. [Game] Removal of stuck cannon balls
   1. Requirement: Several saves with pits to trap the ball. These include:
      • Trapping between border and peg
      • Trapping between border and block
      • Trapping between blocks
      • Trapping between pegs
   2. When a ball has been stuck (or micro-bounces off blocks) for around 10 seconds it will be deleted and all highlighted pegs removed
   3. If the game condition is reached in part 6 the game ends
9. [Game] Power-up activation
   1. Requirement: Several green pegs surrounded lightly by nearby pegs, at least 3-4
   2. Hitting the first green peg should cause nearby pegs to light up
      1. Score of nearby pegs should be added to the score counter at the bottom
   3. Hitting the second one (or by effect of 9.2) should not cause nearby pegs to light up
      1. If the ball falls through it should respawn at the top moving in the same direction as it was when it fell
   4. Hitting the third should show similar reaction to 9.2, and so on so forth.
   5. If 4 green pegs are hit in a single run, the ball only respawns once when it falls out of the game area
   6. If the ball is stuck after hitting the second green peg, the ball is removed as in part 8 without respawn.

Reflection

I think I had designed my code well enough in theory, at least for the scope of PS1-4, even though there were other things I could have done better. Namely, I was stuck using type checking and switch statements instead of polymorphing by inheritance and protocol conformance. Type checking as we all know is not extensible, to change something would likely mean to change a lot of methods, breaking the open-closed principle.

However, to my chagrin I quickly realised that even using protocol conformance could not improve my code quality. For example, if I were to have my pegs and blocks in a level designer conform to a LevelObject protocol, it would be fine and dandy until you realise that you want to store them in a set. In that case you now need LevelObject to inherit Hashable only to realise that now you need to type erase and can no longer form heterogeneous sets of just LevelObjects. Because of that I still wound up having to forgo the benefits of polymorphism that I would have had in Java (if you look at my code for the Model you'll see two sets for both Peg and Block).

Similarly for handling collisions, because the same thing reacts differently when the colliding object is different, it is on the collidee to check the type and decide its next course of action. As such, it seems that there were much that I could not help with.

While I did have to add new fields and change up the internals of some components (e.g. adding a radius component to Peg where previously it was all fixed), I was surprised that the damage (amount of code rework) was well contained within the component and rarely crossed over into other parts, even between sister groups within the same supergroup. This is probably because I had used the adapter pattern with utility structs to disrupt the dependencies between packages (e.g. LevelDesigner.View is completely separate from LevelDesigner.Model due to the ModelViewConverter bridging the gap). As such, I only really needed to change the adapter structs after changing the rest of the affected sub-component.