Scheme Defender is a mimic of the classical game "Galaga", created in Racket. Just like many of our peers, both of us are interested in video games and thought it would be an excellent project to do. Not only did we want something that was challenging, but entertaining as well. Through the development of this project we learned a different approach to making various games through functional programming.
From the numerous libraries available to us in Racket we decided on using the following:
- 2htdp/image: Assist with displaying Images/Sprites
- 2htdp/universe: Assist with interactions between the user and program
- GUI: Creating a friendly to use interface
The player interacts within a field of objects, the ship, enemies, and missile projectiles. Each of the objects are manipulated via data abstraction. For instance, the player ship has a constant (y) coordinate while the user can change it's (x) coordinate with the right/left arrow keys. The (x) coordinate has +1/-1 to it making the player ship move right/left based on the keyboard input. The enemies that the player fights has a recursive procedure implemented that allows them to be spawned continuously until they defeat the player. They also move accordingly to the (x) & (y) coordinate plane.
Additional features include having a scoreboard to keep track of the how many enemy ships the player shot down, and possibly having sound effects from the play-sound library.
Our goal is to have a functioning program that will simulate a "Galaga" like game within the Racket language. This will be the result of combining various libraries in order to complete each component of the game. During the presentation we should be able to display a majority of the functions we planned on doing, such as moving an Image/Sprite, spawning enemies, and firing missiles.
When the project is finished, the game should be able to run based on user decided window size and difficulty, to appropriately create and destroy enemies, update the player's score appropriately, and write-out the final score to a list of high scores.
The first diagram is a prototype of what we expect the game to look like once we are done. The second diagram is the Architecture Diagram depicting how all of the parts of the prototype will interact with each other.
The player will be able to move left and right and shoot towards the enemy ships. The player's movement will be bounded by the edge of the window and will stop at the edge of the window. Any collision between the player and an enemy will end the game early. If the player destroys an enemy, the player's score will increase.
The enemy ships will continuously move down the screen and they will be destroyed if the player shoots them or they will stop being tracked after they move past the bottom of the screen. If the enemy moves past the bottom of the screen the player's score will decrease. Enemies will not spawn on top of other enemy ships and their starting locations will be spaced apart across the screen based on the width of the image.
We had the basic foundation of our project running:
- Getting our Images/Sprite to Display properly
- Keyboard inputs/movement for the Images/Sprite From this implementation we're able to build upon it even further.
Our secondary goal is implementing the follow:
- Window Collision
- Player/Enemies functioning
By the time of presentation we should have the previous goals implemented into the project, while finishing up our remaining one:
- Missile shooting/collision An additional feature we want to include is a scoreboard, displaying High Scores from the player.
For the first milestone, I found some base images for the player and enemies and got the images to display to the screen.
For the second milestone, I worked on getting the enemies to appear at the top of the screen in random locations. The enemies are contained in a list that the map will walk through and change the y-coordinate values of the images. The number of enemies starts at one enemy at level one and the amount of enemies increases by one every level. I used a map to increase the level and the speeds of missiles, enemies, the player, and the rate at which the enemies decide to proceed down the screen.
For the third milestone/Public Presentation, I will be worked on having a live score on the screen update as the player "destroys" an enemy or an enemy passes through the bottom of the screen. The game ends once an enemy has passed the bottom of the screen.
A small bug in the code that we found and couldn't figure out how to fix was that the missiles were not showing up properly. I thought this added a level of complexity and difficulty to the game, so we decided to make this a feature, not a bug.
After planning out our steps for completing the project we decided to split up the workload. The parts that I'll be working on are:
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Keyboard input/movement: Making the sprites move accordingly to the key you pressed. To accomplish this I plan on using the left/right arrow keys as the movement keys for the player spaceship.
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Window collision: Creating bounds within the display window that limits any Images/Sprites that we're using from going off the screen unless specified. Elaborating further form my Keyboard explanation, I decided to have boundaries from the display window.
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Missile shooting/collision: spawning missiles to "destroy" the enemy.
Fulfilling all parts of the plan would allow us to complete the project as intended from the start. However just like other teams, we expect to run into some obstacles while trying to accomplishing everything we need to do.
Overall we were able to accomplish most of what we intended to do, however as Tim mentioned we had a bug with having the missile to display properly.