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We used the Random class in SquareChase to generate random numbers. Since we will need to randomly generate pieces to add to the game board, we need an instance of Random in the GameBoard class.

The Texture2D (playingPieces) and the Rectangle (emptyPiece) will be passed in when the class is created and hold the sprite sheet used to draw the board and the location of the sheet's empty piece square.

The two constants and the boardSquares array provide the storage mechanism for the GamePiece objects that make up the 8x10 piece board. Note that since arrays start counting at 0 instead of 1, we use numbers for the width and height that are one lower than the actual number of board squares. This is a personal preference, but we will be doing a lot of looping over the items in the boardSquares array, and we can either add a -1 to all of the references to our width and height, or declare them as one item smaller to take zero-based arrays into account.

Finally, a list of Vector2 objects is declared that we will use to identify scoring pipe combinations. The List class is one of the .NET Framework's generic collection classes – classes that support the Of notation that we first saw when loading a texture for SquareChase. Each of the Collection classes can be used to store multiple items of the same type, with different methods to access the entries in the collection. We will use several of the Collection classes in our projects. The List class is much like an array, except that we can add any number of values at runtime, and remove values in the List, if necessary.

A Vector2 is a structure defined by the XNA framework that holds two floating point (single) values, X and Y. Together, the two values represent a vector pointing in any direction from an imaginary origin (0, 0) point. We will use Vector2 structures to represent the locations on our game board in Flood Control and off-setting all of our additional drawing based on this location.

Creating the game board

If we were to try to use any of the elements in the boardSquares array at this point, we would get a Null Reference exception, because none of the GamePiece objects in the array have actually been created yet.