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Wee Dig Dug: Design


The game is designed similar to a Model-View-Controller (MVC) framework. This architecture is a common way of designing applications with a User Interface. A MVC framework works in the following way:

  • Each component is responsible for a particular task, and only that component is allowed to perform that task.
  • The Model is the internal representation of the application, and it is responsible to maintain the state of the application at any time.
  • The View is the GUI. It works by reading the Model and displaying the graphical representation of the model on the screen.
  • The Controller is the component that is responsible for listening to user input and updating the model accordingly.
  • MVC components interact with each other the following way:

TODO: Insert MVC image

Controller (controller.s)

The Controller mainly contains interrupt handlers, and it is also the entry point for the game. In is, we do the following:

  • Initialize timer and timer match registers for periodic interrupts.
  • Listen for UART0 interrupt, read the keystrokes and perform the corresponding action
  • Listen for External Interrupt Button press and PAUSE the game.

The controller is a relatively small component, responsible mainly for updating the Model via subroutines exposed by the Model.

Model (model.s)

The Model maintains the internal representation of the board and triggers View updates. It exposed routines that allows the Controller to trigger updates on the Model.


The Model consists of an "array" (created using the FILL directive) of size $19 \times 15$ bytes, each byte representing a grain of sand.

The Model also consists of DCD tables to hold information of sprites. These tables are structured similar to C structs. They look like this:

	DCD [0-18]	; Holds X coordinate of the sprite
	DCD [0-14]	; Holds Y coordinate of the sprite
	DCD {1,4}	; Holds Number of lives the sprite has
	DCD [0-3]	; Code for direction the sprite is moving/facing
	DCD [0-18]	; Previous X coordinate of sprite
	DCD [0-14]	; Previous Y coordinate of sprite
	DCD [0-18]	; Original X position (to reset when respawning)
	DCD [0-14]	; Original Y position

There are also staticaly defined regions of memory that keep track of the various states the game could possibly be in, for example, PAUSE, GAME_OVER. The Model is also responsible for keeping track of other variables of the game, such as, LEVEL, HIGH_SCORE, CURRENT_SCORE and TIME.


Operations that are defined by the Model are:

  • Initialize and reset model.
  • Move sprites and update entire model.
  • Handle and detect collisions.
  • Get if sand exists at given (x,y) coordinate on the board.
  • Clear sand at given coordinate (x,y).
  • Toggle game states (BEGIN_GAME,PAUSE, GAME_OVER, RUNNING).
  • Update individual sprites.
  • Spawn sprites.

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