Talking about The Impossible Line game, Actionscript 3, Flash, Game development and iOS.
As promised, here is the final prototype of The Impossible Line game.
In first step I showed you how to draw following mouse movement.
In second step I showed you how to create the collision radar.
In this big update I am introducing the remaining features:
* Goal: you now have to reach the green circle at the right of the stage.
* Death: happens when you hit a wall.
* Light powerup: in the original game you activate it with an icon, in this version you have to touch it to activate it. I am using the same principle seen in the second step to create the radar, together with some gradient fill to achieve quite the same effect you can see in the original game.
* Replay: once you win or lose the game, you can see the replay of your action. This is an amazing feature which can be done just recording player position at every frame by storing it into a vector, then moving the player according to vector values.
To make everything fit into a quite small and still readable full commented script, I removed some basic features introduce at step 1 such as drawing and rotating.
You should be able to add them by yourself in a matter of seconds. Here is the script:
package {
import flash.display.Sprite;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.display.GradientType;
import flash.geom.Matrix;
import flash.events.Event;
public class Main extends Sprite {
// Arrow is the name class you can find in the library containing the arrow image
private var arrow:Arrow=new Arrow();
// mousePoint is the actual point we are moving the mouse on
private var mousePoint:Point;
// Level is the name of the class you can find in the library storing levels
private var level:Level=new Level();
// Radar is the name of the class you can find in the library storing radar image
private var radar:Radar=new Radar();
// Light is the name of the class you can find in the librart storing light image
private var light:Light=new Light();
// Goal is the name of the class you can find in the librart storing goal image
private var goal:Goal=new Goal();
// lightCanvas is the sprite where we'll display the light
private var lightCanvas:Sprite=new Sprite();
// Boolean variable to see if we collected the light
private var hasLight:Boolean=false;
// vector to store all mouse movements
private var mouseVector:Vector.<Point>=new Vector.<Point>();
// Boolean variable to tell us if we shoud record mouse movements
private var recordMouse:Boolean=false;
// Boolean variable to tell us if we shoud play mouse movements
private var playMouse:Boolean=false;
public function Main() {
// adding the arrow in the upper left corner of the stage
addChild(arrow);
arrow.x=40;
arrow.y=40;
// adding the level to stage
addChild(level);
// adding the radar in the upper right corner of the stage
addChild(radar);
radar.x=600;
radar.y=40;
// placing the light in the middle of the stage
addChild(light);
light.x=320;
light.y=240;
// adding light canvas
addChild(lightCanvas);
// placing the goal in the right end of the stage
addChild(goal);
goal.x=600;
goal.y=240;
// at this time we only have to wait for the player to press the mouse button
stage.addEventListener(MouseEvent.MOUSE_DOWN,mousePressed);
// a listener to give a flickering effect to the light and record mouse movements
addEventListener(Event.ENTER_FRAME,update);
}
private function mousePressed(e:MouseEvent):void {
// the player pressed the mouse so we can start drawing - we don't need to wait for the player to press the mouse
stage.removeEventListener(MouseEvent.MOUSE_DOWN,mousePressed);
// now we must wait for the player to move or release mouse button
stage.addEventListener(MouseEvent.MOUSE_MOVE,mouseMoved);
stage.addEventListener(MouseEvent.MOUSE_UP,mouseReleased);
// saving mouse position
mousePoint=new Point(mouseX,mouseY);
// hiding the level;
level.visible=false;
// let's start recording mouse movements
recordMouse=true;
}
private function mouseMoved(e:MouseEvent):void {
var dx:Number=mouseX-mousePoint.x;
var dy:Number=mouseY-mousePoint.y;
// moving arrow Sprite according to such distances
arrow.x+=dx;
arrow.y+=dy;
// saving current mouse position;
mousePoint.x=mouseX;
mousePoint.y=mouseY;
// a couple of temporary variables
var rayAngle:Number;
// precision is the... precision of the radar system. I suggest a number which divides 360
var precision:Number=20;
// rayStep is the number of steps in pixels the raycast performs to find an obstacle
var rayStep:Number=1;
// default minimum distance is 50 pixels
var minDistance:Number=50;
// looping and looking for the closest point to the arrow
for (var i:Number=0; i<=precision; i++) {
// finding the i-th angle
rayAngle=2*Math.PI/precision*i;
// arrow radius is 16px. We are looking for obstacles closer than 50px. So we must see from 16 to 66
// the bigger rayStep, the faster and less accurate the process
for (var j:Number=16; j<=66; j+=rayStep) {
// here we go, looking for obstacles
if (level.hitTestPoint(arrow.x+j*Math.cos(rayAngle),arrow.y+j*Math.sin(rayAngle),true)) {
// we found it!!
minDistance=Math.min(j-16,minDistance);
break;
}
}
}
// updating radar size;
radar.width=minDistance;
radar.height=minDistance;
// you hit the wall = game over
if (minDistance<1) {
mouseVector.push(new Point(arrow.x,arrow.y));
level.visible=true;
stage.removeEventListener(MouseEvent.MOUSE_MOVE,mouseMoved);
stage.removeEventListener(MouseEvent.MOUSE_UP,mouseReleased);
removeChild(lightCanvas);
removeChild(radar);
recordMouse=false;
playMouse=true;
}
// checking the collision between the arrow and the light, if we still did not pick up the light
if (! hasLight) {
var arrowToLightX:Number=arrow.x-light.x;
var arrowToLightY:Number=arrow.y-light.y;
// 676 = (16 (arrow radius) + 10 (light radius))^2
if (arrowToLightX*arrowToLightX+arrowToLightY*arrowToLightY<676) {
// you got light powerup!!
hasLight=true;
removeChild(light);
}
}
else {
// do you remember the radar? Things are quite similar for the light, we only want more precision
lightCanvas.graphics.clear();
lightCanvas.graphics.lineStyle(0,0xffffff,0);
var mtx:Matrix = new Matrix();
mtx.createGradientBox(232,232,0,arrow.x-116,arrow.y-116);
// we are drawing a gradient this time;
lightCanvas.graphics.beginGradientFill(GradientType.RADIAL,[0xffffff,0xffffff],[0.5,0],[0,255],mtx);
precision=60;
for (i=0; i<=precision; i++) {
rayAngle=2*Math.PI/precision*i;
for (j=16; j<=116; j+=rayStep) {
if (level.hitTestPoint(arrow.x+j*Math.cos(rayAngle),arrow.y+j*Math.sin(rayAngle),true)) {
break;
}
}
if (i==0) {
// moving the graphic pen if it's the first point we find
lightCanvas.graphics.moveTo(arrow.x+j*Math.cos(rayAngle), arrow.y+j*Math.sin(rayAngle));
}
else {
// or drawing if it's not the first point we find
lightCanvas.graphics.lineTo(arrow.x+j*Math.cos(rayAngle), arrow.y+j*Math.sin(rayAngle));
}
}
lightCanvas.graphics.endFill();
}
// checking the collision with the goal;
var arrowToGoalX:Number=arrow.x-goal.x;
var arrowToGoalY:Number=arrow.y-goal.y;
// 1296 = (16 (arrow radius) + 20 (goal radius))^2
if (arrowToGoalX*arrowToGoalX+arrowToGoalY*arrowToGoalY<1296) {
// great! you won!
mouseVector.push(new Point(arrow.x,arrow.y));
level.visible=true;
stage.removeEventListener(MouseEvent.MOUSE_MOVE,mouseMoved);
stage.removeEventListener(MouseEvent.MOUSE_UP,mouseReleased);
removeChild(lightCanvas);
removeChild(radar);
recordMouse=false;
playMouse=true;
}
}
private function mouseReleased(e:MouseEvent):void {
// the player released the mouse. Stop drawing and let's wait for mouse press
stage.removeEventListener(MouseEvent.MOUSE_MOVE,mouseMoved);
stage.removeEventListener(MouseEvent.MOUSE_UP,mouseReleased);
stage.addEventListener(MouseEvent.MOUSE_DOWN,mousePressed);
}
private function update(e:Event):void {
// just flickering the light
lightCanvas.alpha=0.5+Math.random()*0.5;
// recording mouse position
if (recordMouse) {
mouseVector.push(new Point(arrow.x,arrow.y));
}
// playing mouse position
if(playMouse){
var currentPoint:Point=mouseVector.shift();
arrow.x=currentPoint.x;
arrow.y=currentPoint.y;
if(mouseVector.length==0){
removeEventListener(Event.ENTER_FRAME,update);
}
}
}
}
}
And this is the result:
Move the white circle to the green circle avoiding white walls and looking at the red radar. Get the yellow circle to turn on the light. Refresh once you win or die.
Download the source code. Next time, I am going to show you how to port it to iPad using Starling.
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