int WIDTH=799;
int HEIGHT=490;
float ECOL=0.9;
float EDRAG=0.999;
float EG=0.0;
int N;
int NS;
//long CT=0;
int ITT=5;

float[] PX = new float[4];
float[] PY = new float[4];
float[] PX_OLD = new float[4];
float[] PY_OLD = new float[4];

int STICKA[] = new int[5];
int STICKB[] = new int[5];
float STICKLENGTH[] = new float[5];


boolean RUNNING=true;
boolean FRICTION=false;
boolean GRAVITY=true;

void setup() {
  size(800, 550, P2D);
  reset();
}

void draw() {

background(0,0,0,0);
noFill();
stroke(255);
rect(0,0,WIDTH,HEIGHT);

renderbuttons();
//if(CT++>3000) {reset(); RUNNING=false;} //fuze

if (RUNNING) {
updatepoints();

for (int i=0;i<ITT;i++) {
updatesticks();
constrainpoints();
}


}

if (mousePressed && (mouseButton == LEFT) && RUNNING) {nickmouse();}
renderpoints();

}

void renderpoints() {

 
stroke(164,164,164); 
fill(32,32,160);
beginShape();
vertex(PX[0],PY[0]);  
vertex(PX[1],PY[1]);  
vertex(PX[3],PY[3]);  
vertex(PX[2],PY[2]);
vertex(PX[0],PY[0]); 
endShape();
  
}

void updatesticks() {
for (int i=0;i<NS;i++) {
  float dx,dy, dist, diff, percent, offx, offy;
  dx=PX[STICKA[i]]-PX[STICKB[i]];
  dy=PY[STICKA[i]]-PY[STICKB[i]];
  dist=sqrt((dx*dx)+(dy*dy));
  diff=STICKLENGTH[i]-dist;
  percent=diff/dist/2;
  offx=dx*percent;
  offy=dy*percent;
  
  PX[STICKB[i]]-=offx;
  PX[STICKA[i]]+=offx;
  PY[STICKB[i]]-=offy;
  PY[STICKA[i]]+=offy;
}
}


void constrainpoints() {
 
 float VX,VY;

for (int i=0;i<N;i++)
{

  
  VX=(PX[i]-PX_OLD[i])*EDRAG;
  VY=(PY[i]-PY_OLD[i])*EDRAG;


if (PX[i]>WIDTH) 
 {
   PX[i]=WIDTH;
   PX_OLD[i]=(PX[i]+(VX*ECOL));
 }
 else if (PX[i]<0)
  {
    PX[i]=0;
    PX_OLD[i]=(PX[i]+(VX*ECOL));
  }
  
  if (PY[i]>HEIGHT) 
 {
   PY[i]=HEIGHT;
   if(FRICTION) {PX_OLD[i]=PX[i];}
   PY_OLD[i]=(PY[i]+(VY*ECOL));
 }
 else if (PY[i]<0)
  {
    PY[i]=0;
    PY_OLD[i]=(PY[i]+(VY*ECOL));
  }
  
} 

}




void updatepoints() {
 
 float VX,VY;

for (int i=0;i<N;i++)
{
 

  
  VX=(PX[i]-PX_OLD[i])*EDRAG;
  VY=(PY[i]-PY_OLD[i])*EDRAG;

  
  PX_OLD[i]=PX[i];
  PY_OLD[i]=PY[i];
  PX[i]+=VX;
  PY[i]+=VY;
  PY[i]+=EG;

} 

}

void reset() {


  
   N=4;NS=5;
   four();
   STICKA[0]=0;STICKB[0]=1;STICKLENGTH[0]=calclength(0,1);
   STICKA[1]=0;STICKB[1]=2;STICKLENGTH[1]=calclength(0,2);
   STICKA[2]=1;STICKB[2]=3;STICKLENGTH[2]=calclength(1,3);
   STICKA[3]=2;STICKB[3]=3;STICKLENGTH[3]=calclength(2,3);
   STICKA[4]=0;STICKB[4]=3;STICKLENGTH[4]=calclength(0,3);
 

RUNNING=false;
CT=0;
}

void twothree() {
float MX,MY, randr, randangle;
MX=random(120,WIDTH-120);
MY=random(120,300);
randr=random(60,100);

PX[0]=coox(MX,MY,randr,0);
PY[0]=cooy(MX,MY,randr,0);
PX_OLD[0]=PX[0]+(random(-150,150)/10);
PY_OLD[0]=PY[0]+(random(-150,150)/10);

PX[1]=coox(MX,MY,randr,500);
PY[1]=cooy(MX,MY,randr,500);
PX_OLD[1]=PX[1]+(random(-50,50)/10);
PY_OLD[1]=PY[1]+(random(-50,50)/10);

randangle=random(100,400);
PX[2]=coox(MX,MY,randr,randangle);
PY[2]=cooy(MX,MY,randr,randangle);
PX_OLD[2]=PX[2]+(random(-50,50)/10);
PY_OLD[2]=PY[2]+(random(-50,50)/10);
}

void four() {
float MX,MY, randr, randangle, opp, leftv, rightv;
MX=random(120,WIDTH-120);
MY=random(120,300);
randr=random(60,100);
opp=random(400,600);
leftv=random(100,opp-100);
rightv=random(opp+100,900);

PX[0]=coox(MX,MY,randr,0);
PY[0]=cooy(MX,MY,randr,0);
PX_OLD[0]=PX[0]+(random(-150,150)/10);
PY_OLD[0]=PY[0]+(random(-150,150)/10);

PX[3]=coox(MX,MY,randr,opp);
PY[3]=cooy(MX,MY,randr,opp);
PX_OLD[3]=PX[3]+(random(-50,50)/10);
PY_OLD[3]=PY[3]+(random(-50,50)/10);

PX[1]=coox(MX,MY,randr,leftv);
PY[1]=cooy(MX,MY,randr,leftv);
PX_OLD[1]=PX[1]+(random(-50,50)/10);
PY_OLD[1]=PY[1]+(random(-50,50)/10);

PX[2]=coox(MX,MY,randr,rightv);
PY[2]=cooy(MX,MY,randr,rightv);
PX_OLD[2]=PX[2]+(random(-50,50)/10);
PY_OLD[2]=PY[2]+(random(-50,50)/10);


}


float calclength(int p1, int p2) {
float dx2,dy2;
dx2=pow(PX[p1]-PX[p2],2);
dy2=pow(PY[p1]-PY[p2],2);
return sqrt(dx2+dy2);
}

void renderbuttons() {
  textSize(16);
  textAlign(CENTER, CENTER);
  stroke(164,164,164);
  String label;
  
  if(RUNNING) {fill(128,110,0); label="RESET";} else {fill(100,100,100); label="Start";}
  rect(0,510,100,30,4);
  fill(255);
  text(label,50,525);
  
  if(GRAVITY) {fill(128,110,0); label="Gravity"; EG=0.5;} else {fill(100,100,100); label="No Gravity"; EG=0.0;}
  rect(110,510,100,30,4);
  fill(255);
  text(label,160,525);
  
  if(FRICTION) {fill(128,110,0); label="Friction";} else {fill(100,100,100); label="No Friction"; }
  rect(220,510,100,30,4);
  fill(255);
  text(label,270,525);
 
}

void mouseClicked() {
 if ( mouseY>=510 && mouseY<=540 && mouseX>0 && mouseX<100) {RUNNING=!RUNNING; if(!RUNNING) {reset();}}
 if ( mouseY>=510 && mouseY<=540 && mouseX>110 && mouseX<210) {GRAVITY=!GRAVITY;}
 if ( mouseY>=510 && mouseY<=540 && mouseX>220 && mouseX<320) {FRICTION=!FRICTION;}

}

void nickmouse() {


  if (mouseX<WIDTH && mouseY<HEIGHT) { //are we in range
    float dist;
  
    for(int i=0;i<N;i++)
     {
       dist=sqrt(((mouseX-PX[i])*(mouseX-PX[i]))+((mouseY-PY[i])*(mouseY-PY[i])));
       if (dist<=30) {
       //  noFill();
       //  stroke(255);
       // ellipse(PX[i],PY[i],10,10);
        PX[i]=mouseX;PY[i]=mouseY;
        PX_OLD[i]=PX[i];PY_OLD[i]=PY[i];
       } 
   
     }
  }
} 




float coox(float cx, float cy, float r, float t) {
// calculate x coordinate of point on circle t/1000 of 2PI around
return cx+(r*sin(t*TWO_PI/1000));
}

float cooy(float cx, float cy, float r, float t) {
// calculate x coordinate of point on circle t/1000 of 2PI around
return cy+(r*cos(t*TWO_PI/1000));
}