Delivery Kid is a game with classic arcade gameplay. Deliver newspapers to all of the subscribers. Avoid hitting obstacles or the delivery kid will be fired. Break windows and topple garbage cans for bonus score. Are you good enough to complete deliveries through the entire week?
For this game, I am analyzing the gameplay of the source material and will attempt to implement that gameplay in a 3D world using Unity. I am documenting my thought process before I implement each component in order to capture all of the game’s rules in writing. First of all, I identified all of the objects in the game, and I implemented those objects with primitive 3D Unity objects..
Player – The player will be represented by an object with a capsule collider. The capsule collider will allow the player to smoothly move up ramps and other objects. The player will move forward in the world Z axis at a constant rate. If the user presses up on the controls, then the player will move faster. If the user presses down on the controls, the the player will move slower, but not completely stop. The camera will be parented to the player, so that the camera always follows the player.
The player will have a Rigidbody so that it responds to physics, and the X and Z rotation axes will be frozen.
The player starts with three lives. One life is deducted whenever the player collides with a house or enemy. The game is over when the player’s available lives falls below zero. The number of player lives will be displayed on the screen.
The player will have a Playmaker FSM with one state that controls the player movement, using the Get Axis Vector action which stores the user’s input into a Vector3 variable. The player’s location is then translated by that vector in world coordinates.
House – There will be various houses placed in a row on the right side of the bounding box. The objective will be to deliver newspaper to the target houses. Target houses will have a brighter color to differentiate them from the other houses. Each target house will have a mailbox. The house will initially be implemented with a box collider, with a short box trigger surrounding it for the yard. If the player fails to deliver the newspaper to the target house, then it will no longer be a target house on the next level.
Newspaper – The objective is to throw newspapers so that they land in the yard trigger area of the target houses. The player will throw newspapers in the negative X axis towards the houses by pressing an action button on the keyboard, gamepad, or mouse. Some force will need to be applied to the newspaper in the positive Z direction, since the majority of the screen is filled with the world in front of the player. The Z force could possibly be based on how fast the player is moving forward. Newspapers can also be used as weapons to stun enemy characters. The newspaper will contain a sphere collider.
The player starts with a stock of 10 newspapers. One is subtracted whenever a newspaper is thrown. The player cannot throw any newspapers when their stock is zero. The number of newspapers in the players stock will be displayed on the screen.
Newspaper Refill – The newspaper refill object will set the player’s stock back to 10 newspapers. Newspaper refills will appear randomly next to houses.
Mailbox – One mailbox will be available for each target house. Bonus points are awarded for landing a newspaper in the mailbox. The front of the mailbox will have a box trigger. When a newspaper enters the trigger, then the newspaper will stop moving by setting the kinematic value to true. The mailbox will also have a regular collider that surrounds the mailbox object.
LevelManager – There will be a set number of houses for each level. After the player passes the final house, the level is completed. The Level Manager will instantiate the player when the level starts. At the start of each level, the LevelManager will instantiate the Player object.
For the first level, the LevelManager will instantiate twenty houses. Ten random houses will subscribers and the other ten houses will be non-subscriber houses. The subscriber information will be stored in an array of booleans. During the game, another boolean array will track which houses have been delivered a paper. The index for that house will have their delivery set to true if a newspaper is delivered to the mailbox or delivery area. After the level, the subscriber array will be compared with the delivery array. Any subscriber who did not get a delivery will be set as a non-subscriber. The game is over if all houses become non-subscribers.
If the player successfully delivers newspapers to all of the houses that are subscribers, then the player will have a perfect delivery and one of the non subscriber houses will be chosen at random and converted to a subscriber house.
The level number will start at zero and increased by one after reaching the exit object. The level number corresponds with a day of the week, which will be displayed before the beginning of each level.
Enemies – Various types of enemies will try to attack the player. If an enemy collides with the player, then the player loses a life. When all player lives are lost the game is over.
Obstacles – When the player collides with an obstacle, they will lose one life. Unlike enemies, obstacles do no move. Below is a list of obstacles.
Trash Can – Originally 100 points; I think it should be 100 breakage points for unsubscriber
Fence – This could be a part of the house, but I decided to make it a separate non-moving object
Yard Sign – Another non moving object. It displays the house number which starts at 120 and decrements by one for every house.
Breakdancer and Radio – Stationary objects. Breakdancer stops spinning if hit with a newspaper
Brick Barbeque – Stationary object in yard.
Fire Hydrant – Stationary object that is always in the sidewalk.
Car – Cars move in the negative Z direction in world coordinates on the road at a constant velocity. Cars spawn at the end of the street at regular intervals. Cars also spawn at the second and third intersections at random intervals and move in the positive X direction.
Jackhammer Guy – Always spawns on the sidewalk or in the road.
Dog – The dog chases player if player gets too close. The dog move slightly slower than the player, giving the player the chance to escape.
Grates – Grates are always on the edge of the road next to the sidewalk.
Lot – The lot one is gameplay unit where one house resides. There will be a large plane representing the ground area that is not covered by the houses. The lot is the gameplay area where the player can move. The lot consists of the yard around the house, the sidewalk, and the road. This object has a plane collider to prevent the player from falling through the world. There are also two cubes spanning the length of the lot, which are placed on the left and right side side of the ground plane, which are required to keep the player from leaving the gameplay area. The mesh renderer and mesh filter are removed to keep the user from seeing the invisible walls.
Intersection – An intersection is a road that runs horizontally with no houses. There is an intersection at the start of the level, and then intersections after the fifth and tenth lot. The player will need to avoid cars in the second and third intersections. The intersection will also have left and right boundaries to prevent the player from leaving the gameplay area.
Exit – The exit is placed after the last house, and when the player collides with the exit the game will proceed to the level complete state. The exit is an invisible cube collider, and it must be big enough to completely block the player’s path to prevent the player from moving around it.
Score Points – Not an actual object in the world, but there will be a global variable which tracks the number of points that they player has accumulated. Below are the point values associated with various tasks.
Regular paper delivery: 100
Mailbox paper delivery: 250
Hit enemy (lawnmower) with newspaper: 100
Hit breakdancer: 350
A separate point value is kept for breakage bonuses. The breakage values are listed below.
Break window: 100
Break window combo: +25 for each additional window on same house (100 for first window, 125 for second window, 150 for third window, and so forth)
Kitty’s Adventure is a game developed in remembrance of Kitty. Kitty is lost in the maze and only you can help her escape! Guide Kitty to the exit of each maze. Every level is a uniquely generated maze configuration. As you complete the levels with Kitty, the maze complexity increases.
I began development by making a simple cat model in Blender. Next, I textured mapped my model by UV unwrapping the model, by mostly using the “Project from View” operation while selecting specific faces of my model. I exported the UV layout, and then I created the texture map in Gimp. I used the dropper tool get the fur color from a real photo of Kitty. I ended up adding a little more saturation to the colors, as the texture looked a little faded when mapped onto my model. I used the reflect modifier, so that I only had to model and texture map the left side of the body.
I created an armature for my model, with bones for the body, arms, legs, head, and tail. Then I created three animations for my character, which are standing, walking, and jumping.
Next, I created a simple maze in blender by scaling a plane object, and then subdividing it by 20. Then I selected all of the faces that would be walls, and then extruded those upwards by about 1.5 units. I downloaded a flower texture from CGTextures and mapped it as the wall texture.
In my Unity project, I imported my cat model and maze model. I made a capsule game object for the player, and parented the cat model to the Player game object. I used Playmaker for controlling the movement of Kitty with the Get Axis Vector and Translate actions, using “XZ” as the Map to Plane option. It is important to add a mesh collider to the maze model, otherwise Kitty will walk through the walls.
I created four scenes for this game. The “memory” splash screen shows a brief photo of Kitty that fades in and out. The Camera Fade In and Camera Fade Out actions accomplished that effect. However, I had to disable all of the GUIText and GUITexture objects after the fade out, otherwise you would see a flicker for a frame before the next scene is loaded.
I added the title screen last. It just displays the game’s title and waits for the user to press a mouse button to start the game. I added my Kitty model with the walk animation and I applied a constant rotation action to make Kitty spin. It doesn’t look very natural, so I may go back and modify it later.
The game scene is where the bulk of the gameplay occurs. I added entrance and exit objects, which are just cubes with triggers. The entrance really isn’t used now, but walking into the exit cube with transition the game to the final screen. It took me a little while to get the perfect height for the maze walls. If the walls are too tall, then you can’t see Kitty at times. If the walls are too low, then it makes the maze too easy to solve and looks unnatural (why wouldn’t you just step over the walls?).
I also wanted to use controls similar to a Mario 64 style game. Playmaker provides a Smooth Camera Follow action, but it makes the camera always stay behind the character, and only works well when using a control scheme where you press up to go forward, down to go backwards, and left and right to rotate. The control scheme I wanted to use is pressing up to go into the screen, down to go to out of the screen, and left and right to go to the sides of the screen. The camera would need to be set to the position of Kitty with an added offset and never rotate. I couldn’t parent the camera to the player game object, because it would have the camera turn wildly whenever the player’s rotation changed. When the walls were too tall, I would have problems of being able to see through some walls, since the camera was inside of the walls. Ensuring that the camera was always positioned above the top of the walls resolved this problem.
After Kitty reaches the exit, then it transitions to the final game over screen. I have a simple congratulations message with Kitty jumping up and down. At first, the player could still control Kitty on this screen, so I disabled the movement FSMs when the scene is loaded.
At this point, I had a working game, but it was not very complex and it used the same maze every time. I did some research, and I found that Prim’s algorithm can be used to generate mazes. I created a new test scene, just for programming the maze layout. I created a new object and attached a new PrimsMaze script to it. The script takes a game object (maze wall prefab) and the number of rows and columns to use in the maze. I found a good video explaining how to make a maze using Prim’s algorithm, so I wrote a C# script using the method described in the video.
The maze generation works pretty well. I set the exit to the last open space in the last row, although that really isn’t the most elegant solution and could result in problems if there are no open spots in the last row (my Unity editor crashed more than once due to not being able to find an open spot, resulting in losing all work since the last save). One nice thing about Playmaker is that it will detect and break out of infinite loops, however infinite loops in a script will result in the entire Unity editor hanging. There used to be a trick where you would attach the MonoDevelop editor to the Unity process and then change the variable causing the loop, but I couldn’t get that to work with the Visual Studio editor.
Now every time someone plays the game, they get a unique maze. The maze complexity also increases as the player completes the levels. I created a Playmaker global variable to hold the level number, which is incremented at the end of every stage. I recently discovered that Playmaker global variables are accessible from any scene, which is really helpful to keep data (like level number) persistent across scenes. I created a new function in my maze generation script, which has a switch statement that determines how many rows and columns to place in the maze based on the level number. After level six, it uses the default row and column values. I need to do some tests to see how many wall objects I can have before the game experiences slowdown.
There are a few more features I want to add to the Kitty’s Adventure game. Obviously, I need to add music and sound effects. I’ve also had the idea of adding paw prints on the ground as Kitty walks around the maze, which would be like breadcrumbs showing the areas where you have already been. There are plenty of obstacles that could be added to the maze. It would also be nice to have a timer showing how long it has taken to complete each maze.