Talking about Plants Vs Zombies game, Actionscript 3, Flash and Game development.
After a little pause, here we go with the 5th step of the tutorial.
In this step we’ll fix a bug which allowed plants to fire even if there isn’t any enemy coming from the right side, when there’s at least one enemy on the left side, and we’ll see zombies attacking the plants.
First, let me explain some changes: during previous steps, zombiesArray array was used only to count the number of zombies walking in each row. This information isn’t enough for us to know whether the zombies are on the left or on the right side of each plant, so from now on zombiesArray is an array of arrays filled with the names of the zombies walking in each row.
You’ll understand this feature better when we’ll discuss the source code.
To make zombies attack plants, we must stop them once they are on the same tile the plant is placed on.
Let’s see the source code:
package {
import flash.display.Sprite;
import flash.utils.Timer;
import flash.events.TimerEvent;
import flash.events.MouseEvent;
import flash.events.Event;
import flash.text.TextField;
public class Main extends Sprite {
//
// arrays to store game field information
//
private var plantsArray:Array;// plants placed in the game field
private var zombiesArray:Array;//zombies placed in the game field
//
// timers
//
private var flowersTimer:Timer=new Timer(5000);// timer to make flowers fall down
private var zombieTimer:Timer=new Timer(5000);// timer to make zombies come in
//
// containers
//
private var sunContainer:Sprite=new Sprite();// container for all suns
private var plantContainer:Sprite=new Sprite();// container for all plants
public var bulletContainer:Sprite=new Sprite();// container for all bullets
private var zombieContainer:Sprite=new Sprite();// container for all zombies
private var overlayContainer:Sprite=new Sprite();// container of all overlays
//
// actors
//
private var movingPlant:plantMc;// plant the player can drag on game field
private var selector:selectorMc;// the selector square to show the playere where he's going to place the plant
//
// other variables
//
private var money:uint=0;// amout of money owned by the player
private var moneyText:TextField=new TextField ;// dynamic text field where to show player's money
private var playerMoving:Boolean=false;// Boolean variable to tell us if the player is moving a plant (true) or not (false)
private var totalZombies:uint=0;//total amount of zombies placed in game
public function Main():void {
setupField();// initializes the game
drawField();// draws the game field
fallingSuns();// initializes the falling suns
addPlants();// initialized the plants
addZombies();// initializes the zombies
addEventListener(Event.ENTER_FRAME,onEnterFrm);
}
//
// game field setup. arrays to store plants and zombies information are created
//
private function setupField():void {
plantsArray=new Array();
zombiesArray=new Array();
for (var i:uint=0; i<5; i++) {
plantsArray[i]=new Array();
zombiesArray[i]=new Array();
for (var j:uint=0; j<9; j++) {
plantsArray[i][j]=0;
}
}
}
//
// showing the amount of money
//
private function updateMoney():void {
moneyText.text="Money: "+money.toString();
}
//
// game field drawing and children hierarchy management
//
private function drawField():void {
var fieldSprite:Sprite=new Sprite();
var randomGreen:Number;
addChild(fieldSprite);
fieldSprite.graphics.lineStyle(1,0xFFFFFF);
for (var i:uint=0; i<5; i++) {
for (var j:uint=0; j<9; j++) {
randomGreen=(125+Math.floor(Math.random()*50))*256;
fieldSprite.graphics.beginFill(randomGreen);
fieldSprite.graphics.drawRect(25+65*j,80+75*i,65,75);
}
}
addChild(sunContainer);
addChild(plantContainer);
addChild(bulletContainer);
addChild(zombieContainer);
addChild(overlayContainer);
overlayContainer.addChild(moneyText);
updateMoney();
moneyText.textColor=0xFFFFFF;
moneyText.height=20;
}
//
// zombies initialization
//
private function addZombies():void {
zombieTimer.start();
zombieTimer.addEventListener(TimerEvent.TIMER,newZombie);
}
//
// adding a new zombie
//
private function newZombie(e:TimerEvent):void {
var zombie:zombieMc=new zombieMc();// constructs the zombie
totalZombies++;
zombieContainer.addChild(zombie);// adds the zombie
zombie.zombieRow=Math.floor(Math.random()*5);// chooses a random row where to place the zombie
zombie.name="zombie_"+totalZombies;//gives a name to the zombie
zombiesArray[zombie.zombieRow].push(zombie.name);// adds the zombie in the row-th row
zombie.x=660;// places the zombie on the board, outside the stage to the right
zombie.y=zombie.zombieRow*75+115;
}
//
// suns initialization
//
private function fallingSuns():void {
flowersTimer.start();
flowersTimer.addEventListener(TimerEvent.TIMER, newSun);
}
//
// adding a new sun
//
private function newSun(e:TimerEvent):void {
var sunRow:uint=Math.floor(Math.random()*5);// random row
var sunCol:uint=Math.floor(Math.random()*9);// random column
var sun:sunMc = new sunMc();// constructs the sun
sun.buttonMode=true;// makes the mouse change shape when over the plant
sunContainer.addChild(sun);// adds the sun
sun.x=52+sunCol*65;// places the sun in the proper column
sun.destinationY=130+sunRow*75;// definines the sun y destination point
sun.y=-20;// places the sun out to the upper side of the stage
sun.addEventListener(MouseEvent.CLICK,sunClicked);// listener to be triggered when the sun is clicked
}
//
// handling clicks on suns
//
private function sunClicked(e:MouseEvent):void {
e.currentTarget.removeEventListener(MouseEvent.CLICK,sunClicked);// removes the CLICK listener
money+=5;// makes the player earn money (5)
updateMoney();// updates money text
var sunToRemove:sunMc=e.currentTarget as sunMc;// defines which sun we need to remove
sunContainer.removeChild(sunToRemove);// removes the sun
}
//
// building the plant toolbar (only 1 plant at the moment)
//
private function addPlants():void {
var plant:plantMc=new plantMc();// constructs a new plant
overlayContainer.addChild(plant);// adds the plant
plant.buttonMode=true;// makes the mouse change shape when over the plant
plant.x=90;
plant.y=40;
plant.addEventListener(MouseEvent.CLICK,onPlantClicked);// listener to be triggered once the plant is clicked
}
//
// handling clicks on plants
//
private function onPlantClicked(e:MouseEvent):void {
// let's see if the player has enough money (10) to afford the plant and isn't currently dragging a plant
if (money>=10&&! playerMoving) {
money-=10;// pays the plant
updateMoney();// updates money text
selector=new selectorMc();// constructs a new selector
selector.visible=false;// makes the selector invisible
overlayContainer.addChild(selector);// adds the selector
movingPlant=new plantMc();// constructs a new moving plant
movingPlant.addEventListener(MouseEvent.CLICK,placePlant);// lister to be triggered once the moving plant is clicked
overlayContainer.addChild(movingPlant);// adds the moving plant
playerMoving=true;// tells the script the player is actually moving a plant
}
}
//
// placing the plant on the game field
//
private function placePlant(e:MouseEvent):void {
var plantRow:int=Math.floor((mouseY-80)/75);
var plantCol:int=Math.floor((mouseX-25)/65);
// let's see if the tile is inside the game field and it's free
if (plantRow>=0&&plantCol>=0&&plantRow<5&&plantCol<9&&plantsArray[plantRow][plantCol]==0) {
var placedPlant:plantMc=new plantMc();// constructs the plant to be placed
placedPlant.name="plant_"+plantRow+"_"+plantCol;// gives the plant a name
placedPlant.fireRate=75;// plant fire rate, in frames
placedPlant.recharge=0;// plant recharge. When recharge is equal to fireRate, the plant is ready to fire
placedPlant.isFiring=false;// Boolean value to tell if the plant is firing
placedPlant.plantRow=plantRow;// plant row
plantContainer.addChild(placedPlant);// adds the plant
placedPlant.x=plantCol*65+57;
placedPlant.y=plantRow*75+115;
playerMoving=false;// tells the script the player is no longer moving
movingPlant.removeEventListener(MouseEvent.CLICK,placePlant);// removes the CLICK listener from the draggable plant
overlayContainer.removeChild(selector);// removes the selector
overlayContainer.removeChild(movingPlant);// removes the plant itself
plantsArray[plantRow][plantCol]=1;// updates game array adding the new plant
}
}
//
// core function to be executed at every frame. The whole game is managed here
//
private function onEnterFrm(e:Event):void {
var i:int;
var j:int;
//
// plants management
//
for (i=0; i0) {
// let's scan through all zombies
for (j=0; j0; j++) {
var targetZombie:zombieMc=zombieContainer.getChildByName(zombiesArray[currentPlant.plantRow][j]) as zombieMc;// gets the j-th zombie
// if the zombie is on the right of the plant
if (targetZombie.x>currentPlant.x) {
var bullet:bulletMc=new bulletMc();// constructs a new bullet
bulletContainer.addChild(bullet);// adds the bullet
bullet.x=currentPlant.x;
bullet.y=currentPlant.y;
bullet.sonOf=currentPlant;// sets the bullet as a son of the current plant
currentPlant.recharge=0;// the plant must recharge
currentPlant.isFiring=true;// the plant is firing
break;// exits the j for loop
}
}
}
}
// let's see if the plant has to recharge
if (currentPlant.recharge650) {
firingPlant.isFiring=false;// the plant is not longer firing
bulletContainer.removeChild(movingBullet);// removes the bullet
} else {
for (j=0; j8||plantsArray[movingZombie.zombieRow][zombieColumn]==0) {
movingZombie.x-=0.5;// moves each zombie left by 1/2 pixels
} else {
// the zombie attacks!!
var attackedPlant:plantMc=plantContainer.getChildByName("plant_"+movingZombie.zombieRow+"_"+zombieColumn) as plantMc;
attackedPlant.alpha-=0.01;// drains plant energy
// let's see if the plant died
if (attackedPlant.alpha<0) {
plantsArray[movingZombie.zombieRow][zombieColumn]=0;//removes the plant from the array
plantContainer.removeChild(attackedPlant);//removes the plant Display Object from Display List
}
}
}
//
// suns management
//
for (i=0; i=0&&plantCol>=0&&plantRow<5&&plantCol<9) {
selector.visible=true;// shows the selector
selector.x=25+plantCol*65;
selector.y=80+plantRow*75;
} else {
selector.visible=false;// hide the selector
}
}
}
}
}
In setupField function note how zombiesArray becomes an array of arrays, with one element for each row:
private function setupField():void {
plantsArray=new Array();
zombiesArray=new Array();
for (var i:uint=0; i<5; i++) {
plantsArray[i]=new Array();
zombiesArray[i]=new Array();
for (var j:uint=0; j<9; j++) {
plantsArray[i][j]=0;
}
}
}
Then in newZombie function in zombiesArray we push the name of the zombie in the appropriate element according to zombie's row:
private function newZombie(e:TimerEvent):void {
var zombie:zombieMc=new zombieMc();// constructs the zombie
totalZombies++;
zombieContainer.addChild(zombie);// adds the zombie
zombie.zombieRow=Math.floor(Math.random()*5);// chooses a random row where to place the zombie
zombie.name="zombie_"+totalZombies;//gives a name to the zombie
zombiesArray[zombie.zombieRow].push(zombie.name);// adds the zombie in the row-th row
zombie.x=660;// places the zombie on the board, outside the stage to the right
zombie.y=zombie.zombieRow*75+115;
}
Now the whole process of determining if a plant can fire is a bit changed:
if (currentPlant.recharge==currentPlant.fireRate&&! currentPlant.isFiring) {
// let's see if there are zombies in the same row of the plant
if (zombiesArray[currentPlant.plantRow].length>0) {
// let's scan through all zombies
for (j=0; j0; j++) {
var targetZombie:zombieMc=zombieContainer.getChildByName(zombiesArray[currentPlant.plantRow][j]) as zombieMc;// gets the j-th zombie
// if the zombie is on the right of the plant
if (targetZombie.x>currentPlant.x) {
var bullet:bulletMc=new bulletMc();// constructs a new bullet
bulletContainer.addChild(bullet);// adds the bullet
bullet.x=currentPlant.x;
bullet.y=currentPlant.y;
bullet.sonOf=currentPlant;// sets the bullet as a son of the current plant
currentPlant.recharge=0;// the plant must recharge
currentPlant.isFiring=true;// the plant is firing
break;// exits the j for loop
}
}
}
}
We are now scanning zombie by zombie in the same row the plant is placed on, looking for a zombie on the right of the plant (line 214).
Zombies now can attack with these simple lines:
var zombieColumn:int;
for (i=0; i8||plantsArray[movingZombie.zombieRow][zombieColumn]==0) {
movingZombie.x-=0.5;// moves each zombie left by 1/2 pixels
} else {
// the zombie attacks!!
var attackedPlant:plantMc=plantContainer.getChildByName("plant_"+movingZombie.zombieRow+"_"+zombieColumn) as plantMc;
attackedPlant.alpha-=0.01;// drains plant energy
// let's see if the plant died
if (attackedPlant.alpha<0) {
plantsArray[movingZombie.zombieRow][zombieColumn]=0;//removes the plant from the array
plantContainer.removeChild(attackedPlant);//removes the plant Display Object from Display List
}
}
}
We see if there is a plant on the same tile the zombie is walking on, and if true the zombie stops walking and starts draining plant's life (alpha channel in this case).
This is the result:
You should know how to play. Try to get your plant killed by a zombie.
Download the source code. Next time, it will be interesting to describe attack waves and show real energy bars.
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