celly bunches[];
int cellmax = 200;
int celln;
BImage source;
int bottom[];

void addcell(int x, int y, color col) { 
  if ( celln == cellmax ) { 
    cellmax = cellmax << 1;
    celly temp[] = new celly[cellmax];
    System.arraycopy( bunches, 0, temp, 0, bunches.length );
    bunches = temp;
  }
  bunches[celln++] = new celly ( x, y, col );
}

void setup() { 

size ( 80, 360 );
bunches = new celly[cellmax];
background(#000000);
source = loadImage("bush.jpg");
image ( source, 0, 0 );
bottom = new int[source.width];
for ( int i = 0 ; i < source.width; i++ ) { 
  bottom[i] = source.height-1;
}
}

boolean gempty( int x, int y ) { 
  if ( source.get( x, y ) == #000000 ) return true;
  return false;
}

void loop()  { 
  //if ( mousePressed ) { 
  if ( celln < width * source.height ) { 
    for ( int j = 0 ; j < width/4 ; j++ ) { 
      int rx = int( random(width));
      int ry = bottom[rx]--;
      if ( ry >= 0 ) { 
        addcell (rx, ry, source.get( rx, ry ) ) ;
        source.set( rx, ry, #000000 );
      }
  //}
    }
  }
  if ( celln > 0 ) { 
    for ( int i = 0 ; i < celln; i++ ) { 
//      bunches[int( random(celln-1))].behave();
      bunches[i].behave();
    }
  }

}

class celly { 
  int x;
  int y;
  color col;
  celly ( int x, int y, color col ) { 
    this.x = x;
    this.y = y;
    this.col = col;
    set( x, y ,col );
  }
  
  void behave() { 
    //fall down
    
    if ( y < mouseY ) { 
      if ( empty( 0, 1 ) ) { 
        if ( empty( 1, 1 ) || empty( -1, 1 ) ) { 
          move ( 0, 1 ); return; 
        }
      }
    }
    else { 
      int xr = int( random ( -2, 2 ));
      if ( empty ( xr, 1 ) ) {  
        move ( xr, 1 ); return;
      } 
    }
    
    if ( empty ( 1, 0 ) && empty ( 1, 1 ) && empty ( 1, 2 ) ) { move( 1, 2 ); return ; } 
    if ( empty ( -1, 0 ) && empty ( -1, 1 ) && empty ( -1, 2 ) ) { move( -1, 2 ); return ; } 
     
    if ( empty ( 0, -1 ) ) { 
      if ( mouseY < y ) { 
          if ( mouseX > x ) { 
            if ( empty( 1, 0  ) ) { move ( 1, 0 ); return; } 
            if ( empty( 1, -1 ) ) { move ( 1, -1 ); return; } 
          }
          else if ( mouseX < x ) { 
            if ( empty( -1, 0 ) ) { move ( -1, 0); return; } 
            if ( empty( -1, -1 ) ) { move ( -1, -1 ); return; } 
          }
      }
    }
    if ( y <= mouseY ) { 
      if ( full( 1, 0 ) && full ( -1, 0 ) && full ( 0, -1 ) /* && full ( 1,-1 ) && full ( -1, -1 )*/ ) { 
        int yd = 0;
        while ( yd < y && full ( 0, -yd ) ) yd++;
        if ( yd != y ) move ( 0, -yd );
      }   
    }
    if ( !empty ( 0, -1 ) ) { 
      int up = -1;
      while ( up > -x && !empty ( 0, up ) && brightness ( look ( 0, up ) ) < brightness ( col ) ) up--;
      if ( up > -x && empty ( 0, up ) ) { 
        move ( 0, up );
        return;
      }
    }
//    if ( full ( 0 , 1 ) ) { 
//      if ( red(look(0,1)) < red( look(0,0)) ) swap ( other ) ;  
//    }
  }
  
  
  
  void move(int dx, int dy) { 
    int px = max( 0, min( width-1 , x+dx) );
    int py = max( 0, min( height-1, y+dy ) );
    set(x, y, #000000 );
    x = px;
    y = py;
    set(x, y, col);
  }
  
  void swap(celly other) { 
    int tx = other.x;
    int ty = other.y;
    other.x = x;
    other.y = y;
    x = tx;
    y = ty;
    set( other.x, other.y, other.col );
    set( x, y, col );
  }
  
  color look( int dx, int dy ) { 
    int px = max( 0, min( width-1 , x+dx) );
    int py = max( 0, min( height-1, y+dy ) );
    return get(px, py);
  }
  
  boolean full ( int dx, int dy ) { return !empty(dx,dy); }
  boolean empty( int dx, int dy ) { 
    if ( x + dx < 0 || x + dx >= width ) return false;
    if ( y + dy < 0 || y + dy >= height ) return false;
    if ( look(dx, dy) == #000000  ) return true;
    return false;
  }
  
}