Grid based Games – Part 5.2: Towers

This post enhances the previous post by the ability of actually placing obstacles which somewhen may become towers.

Here is what we are going to create:

To have interaction with stage we will set up an EventListener for clicks. First of all we declare a variable named building and set its value according to the actual node. Therefore the mouseMoveHandler function has to be slightly changed:

var building = false;

function mouseMoveHandler ( event:MouseEvent )
{
	var actNode = getPos ( mouseX - size*0.5 , mouseY - size*0.5);
	with ( overlay.graphics )
	{
		clear();
		if ( actNode )
		{
			if ( actNode.blocked )
			{
				building = false;
				beginFill(0x990000, 0.5);
				lineStyle(1, 0x990000, 1);
				drawRect(actNode.x - size*0.5, actNode.y - size*0.5, size*2, size*2);
				endFill();
			}
			else
			{
				building = true;
				beginFill(0x009900, 0.5);
				lineStyle(1, 0x009900, 1);
				drawRect(actNode.x - size*0.5, actNode.y - size*0.5, size*2, size*2);
				endFill();
			}
		}
	}
}

We then add a new movieclip to draw what we have built and and again add the overlay to have it on top.

var buildMap:MovieClip = new MovieClip();
addChild(buildMap);
addChild(overlay);
stage.addEventListener(MouseEvent.CLICK, buildTower);

function buildTower ( event:MouseEvent )
{
	if ( building )
	{
		var actNode = getPos ( mouseX - size*0.5 , mouseY - size*0.5);
		with ( buildMap.graphics )
		{
			beginFill(0x000099, 1);
			lineStyle(1, 0xffffff, 1);
			drawRect(actNode.x - size*0.5, actNode.y - size*0.5, size*2, size*2);
			endFill();
		}
		var actArray = getNeighbors ( actNode );
		for each ( var nObj in actArray )
		{
			nObj.blocked = true;
		}
		actNode.blocked = true;
	}
}

By clicking a new rectangle is drawn to the buildMap on the actual node’s position and the node as well as its neighbors are blocked for further building.

function posToNode ( u, v )
{
	var nodeString = u + "." + v;
	var nodePos = posArray.indexOf(nodeString);
	if ( nodePos > -1 )
	{
		return ( nodeArray[nodePos] );
	}
	else
	{
		return null;
	}
}

posToNode does nothing more than concatenating u and v, looking it up in the posArray and returning the node. This is done for every adjacent node via the getNeighbors function:

function getNeighbors ( centerNode )
{
	var thisU = centerNode.u;
	var thisV = centerNode.v;
	var resultArray:Array = new Array();
	resultArray.push ( posToNode ( thisU - 1, thisV - 1 ) );
	resultArray.push ( posToNode ( thisU - 1, thisV ) );
	resultArray.push ( posToNode ( thisU - 1, thisV + 1 ) );
	resultArray.push ( posToNode ( thisU, thisV + 1 ) );
	resultArray.push ( posToNode ( thisU + 1, thisV + 1 ) );
	resultArray.push ( posToNode ( thisU + 1, thisV ) );
	resultArray.push ( posToNode ( thisU + 1, thisV - 1 ) );
	resultArray.push ( posToNode ( thisU, thisV - 1 ) );
	return resultArray;
}

With that we are now able to place obstacles on the playground. Placing is only possible on unblocked nodes.

Try it. What now? Yoho!

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One Response to Grid based Games – Part 5.2: Towers

  1. Pingback: Grid based games – Part 5.3: Pathfinding « YARR!cade.com LÞ the kegogrog blog

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