Creating the Color Drop Casual Puzzle Game - The Essential Guide to Flash Games - page 338

The TileSheet ( ts ) was created and passed to Block by ColorDrop . Block does not own its own
TileSheet , which means we don't have to create multiple versions of the TileSheet for each
Block and waste memory. Alternatively, we could have made tileSheet a static class variable.
However, we think that passing in the value for the tileSheet helps keep the Block class a bit
more universal and reusable. As well, it keeps us from having to write any code to determine if
tileSheet exists yet and if it needs to be initialized as a class variable.
The next thing we need to do is determine the tile from the sheet that will represent this Block 's
color. Since the color is stored in blockColor , and the values of the Block.BLOCK_COLOR_XXX static
constants represent the order of the colors on the tile sheet, we can easily calculate which tile will
represent this Block like so: tile = blockColor;
Finally, we call the constructor of BlitSprite with the code super(tileSheet, [tile], 0) . The
first parameter is the TileSheet , which we have already described. The second parameter is an
array of tile indexes for this instance to animate through. Since our Blocks do not animate, we
simple put a single value in the array (the value of tile ). The third parameter is the index of the
starting tile in the tiles array. Since we only have one tile, the index is 0 .
We also need to have this Block fire off a MouseEvent if the player clicks it, so we add a
MOUSE_DOWN event that will call the function onMouseDownListener . We also set buttonMode and
useHandCursor to true , so when the mouse pointer rolls over the Block , we will prompt to the user
to click with a recognizable hand cursor. Finally, we call startFalling to have the Block start
moving down the screen.
public function Block(color:Number,tileSheet:TileSheet,row:Number,col:Number,

endY:Number,speed:Number) {

blockColor = color;
this.row = row;
this.col = col;
isFalling = false;
isFading = false;
var tile:Number = blockColor;
super(tileSheet, [tile], 0);
this.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDownListener, false, 0, true);

this.buttonMode = true;
this.useHandCursor = true;
startFalling(endY,speed);
}

The startFalling function is the first link in developing this game into a drop-style game where
blocks fall into place. The heart of the function is the speed and fallEndY instance variables. The
distance between the starting y position of the Block (set by Game) and fallEndY should be
evenly divisible by speed, but it does not have to be. If it is, the Blocks will fall into place
smoother, but the gameplay won't be affected. We set the isFalling variable to true so that
update and render functions will process the Block movement when they are called by Game .
public function startFalling(endY:Number,speed:Number):void {
this.speed = speed;
fallEndY = endY;
isFalling = true;
}
The startFade function is called by ColorDrop to start the Block fading from the screen when the
level ends. The fade is stopped by setting the isFading Boolean to true . The fadeValue passed