exercise 2.1 balloons

[Densou]

Below is my solution for exercise 2.1, balloons.

//code by Densou
//email: tzdensou@gmail.com

Balloon[] balloons= new Balloon[10];

void setup(){
size(600,400);
smooth();
for(int i=0; i<balloons.length;i++){
balloons[i]= new Balloon(i);
}

}

void draw(){
background(200,40,60);

for(int i=0; i<balloons.length;i++){
balloons[i].render();
balloons[i].update();
balloons[i].checkCollision();
}

}

class Balloon{
//v for velocity
//f for acceleration of flotage
//r for acceleration of resistance
//l for location
//a for total acceleration
//wind force
PVector v, f, l, a, wind;
//w,h:size of this balloon
//stringl:string length
//sw: string swing range
//maxV stands for the max velocity a balloon can reach--
//when gracity and flotage get balance
float w,h, maxV,stringl,sw;
//covenient for array
int array;
//color of each balloon
color c;

Balloon(int array_){
v= new PVector(0,0);
//f= new PVector(0,-0.02);
//f minus 0.01, in case acceleration too small
f= new PVector(0,random(0.02)-1-0.01);
maxV= 2.5;
w=random(15)+30;
h=random(10)+w1.2;
//l= new PVector(width/2,height);
l = new PVector(random(width),random(height/2)+height*.5);
stringl=80.0;
sw=40;
array=array_;
c=color(random(150)+100,random(150)+100,random(150)+100);
//c=color(array%3150,(array+2)%3150,(array+1)%3*150);
}

void update(){
wind= new PVector((noise(1,frameCount/200)-0.5)*0.04,(noise(2,frameCount/200)-0.5)*0.01);
a=PVector.add(f,wind);//use static function here, otherwise a increases.
//println(a.x,a.y);
v.add(a);
l.add(v);
//println(v.y);
v.limit(2.2);
//if(v.y>maxV ){
// v.y=maxV;
//}else if(v.y<-maxV){
// v.y=-maxV;
//}
}

void render(){
pushMatrix();
translate(l.x,l.y+h/2);
//swinging string
stroke(242,192,86);
strokeWeight(1);
noFill();
float t=frameCount/500.0;
bezier(
0,0,
0,noise(1,array,t)*stringl-stringl/2,
noise(2,array,t)*sw-sw/2,noise(3,array,t)stringl0.6,
noise(4,array,t)*sw-sw/2,noise(5,array,t)*stringl
);

//balloon ball
//fill(220,30,100);
fill(c);
noStroke();
//ellipse(l.x,l.y,w,h);
ellipse(0,-h/2,w,h);
popMatrix();

}

void checkCollision(){
if(l.y<h/2){
v.y=v.y*-0.8;
f.y=f.y0.8;
if(v.y<0.02 && -0.02<v.y){
v.y=0;
f.y=0;
l.y=h/2;
}
}
//println(v.y);
if(l.x<w/2 || l.x>width-w/2){
v.x=v.x-0.6;
}
}
}