int[][]b=new int[4][4];
int pad=20,bs=100,len=pad*(b.length+1)+bs*b.length,score=0,dead=0;
void setup()
{
 size(500,500);
 restart();
 textFont(createFont("Courier",40));
}

void restart()
{
 b=new int[4][4];
 
 for(int i=0;i<4;i++)for(int j=0;j<4;j++)b[i][j]=0;
 
 score=dead=0;
 noStroke();
 spawn();

 }

void spawn(){
    ArrayList<Integer> xs=new ArrayList<Integer>(),ys=new ArrayList<Integer>();
    for(int j=0;j<b.length;j++)
    {
     for(int i=0;i<b[j].length;i++)
    {  
      if(b[j][i]==0)
      {
        xs.add(i);
        ys.add(j);
      }
    }
    }
    int rnd=(int)random(0,xs.size()),y=ys.get(rnd),x=xs.get(rnd);
    b[y][x]=random(0,1)<0.9?2:4;
    
}


void draw()
{
 background(255); 
  
  rectt(0,0,width,height,10,color(150));
  for(int j=0;j<b.length;j++)
  {
  for(int i=0;i<b[j].length;i++)
  {
    float x=pad+(pad+bs)*i;
    float y=pad+(pad+bs)*j;
    
    rectt(x,y,bs,bs,5,color(200));
     if(b[j][i]>0){
       float p=log(b[j][i])/log(2);
       rectt(x,y,bs,bs,5,color(255-p*255/11,p*255/11,0));
       textt(""+b[j][i],x,y+22,bs,bs,color(0),30,CENTER);
     }

} 
  }
  textt("score: "+score,10,5,100,50,color(0),10,LEFT);
  if(dead>0)
  {
    rectt(0,0,width,height,0,color(255,199)); 
    textt("Game Over ! Click to Restart",0,height/2,width,50,color(0),30,CENTER);
    if(mousePressed)restart();
  }
}

void rectt(float x,float y,float w,float h,float r,color c)
{
  
 fill(c);
 rect(x,y,w,h,r);
  
}

void textt(String t,float x,float y,float w,float h,color c,float s,int align)
{
 fill(c);textAlign(align);textSize(s);text(t,x,y,w,h); 
}

boolean gameover()
{
int[]dx={1,-1,0,0},dy={0,0,1,-1};
boolean out=true;

for(int i=0;i<4;i++)if(go(dy[i],dx[i],false)!=null)out=false;
  return out;
}


void keyPressed()
{
 if(dead==0)
 {
  int kC=keyCode,dy=(kC==UP?-1:(kC==DOWN?1:0)),dx=(kC==LEFT?-1:(kC==RIGHT?1:0));
  int[][]newb=go(dy,dx,true);
  
  
  
  if(newb!=null)
  {
    b=newb;
    spawn();
  }
  if(gameover())dead=1;
  
 }
  
}



int[][] go(int dy,int dx,boolean updateboard)
{
  int [][]bak=new int[4][4];
  for(int j=0;j<4;j++)    for(int i=0;i<4;i++)bak[j][i]=b[j][i];
    
  
  boolean moved=false;
  if(dx!=0 || dy!=0){
   int d=dx!=0?dx:dy;
   for(int perp=0;perp<b.length;perp++)
     for(int tang=(d>0?b.length-2:1); tang!=(d>0?-1:b.length); tang-=d){
       int y=(dx!=0?perp:tang),x=(dx!=0?tang:perp),ty=y,tx=x;
       if(bak[y][x]==0)continue;
       
       for(int i=(dx!=0?x:y)+d;i!=(d>0?b.length:-1);i+=d){
        int r=dx!=0?y:i,c=dx!=0?i:x;
        if(bak[r][c]!=0 && bak[r][c]!=b[y][x])break;
        if(dx!=0)tx=i;
        else ty=i;
        }
        if((dx!=0 && tx==x) || (dy!=0 && ty==y))continue;
        else if(bak[ty][tx]==b[y][x]){
         bak[ty][tx]*=2;
     
         if(updateboard)score+=bak[ty][tx];
          moved=true;  
       }
        else if((dx!=0 && tx!=x) || (dy!=0 && ty!=y))
        {
           bak[ty][tx]=bak[y][x];
           moved=true;
        }
        if(moved) bak[y][x]=0;
     }
     
   }
    
  return moved? bak:null;
}