// 2D Array of objects
Cell[][] grid;

// Number of columns and rows in the grid
int cell_width = 40;

int width;
int height;

int cols;
int rows;

void setup() {
  colorMode(RGB);
  width = displayWidth;
  height = displayHeight;
  size(width,height);
  cols = width / cell_width;
  rows = height / cell_width;
  grid = new Cell[cols][rows];
  for (int i = 0; i < cols; i++) {
    for (int j = 0; j < rows; j++) {
      // Initialize each object
      grid[i][j] = new Cell(i*cell_width,j*cell_width,cell_width,cell_width);
    }
  }
}

void draw() {
  background(255);
  // The counter variables i and j are also the column and row numbers and 
  // are used as arguments to the constructor for each object in the grid.  
  for (int i = 0; i < cols; i++) {
    for (int j = 0; j < rows; j++) {
      // Oscillate and display each object
      grid[i][j].oscillate();
      grid[i][j].display();
    }
  }
}

// A Cell object
class Cell {
  // A cell object knows about its location in the grid as well as its size with the variables x,y,w,h.
  float x,y;   // x,y location
  float w,h;   // width and height
  float red;
  float green;
  float blue;
  float transparent;

  // Cell Constructor
  Cell(float tempX, float tempY, float tempW, float tempH) {
    x = tempX;
    y = tempY;
    w = tempW;
    h = tempH;
    red = random(255);
    transparent = random(255);
    makeGray();
  } 
  
  // Oscillation means increase angle
  void oscillate() {
    if(mousePressed == true) {
      if(mouseX > x && mouseX < (x + h * 2) && mouseY > y && mouseY < (y + w * 2)) {
        red = 200;
        green = 50;
        blue = 0;
      }
    }
    transparent += 0.7;
    if(transparent > 255) {
      transparent = 0;
      red = random(255);
      makeGray();
    }
  }

  void display() {
    stroke(255);
    fill(red, green, blue, transparent);
    rect(x,y,w,h); 
  }
  
  void makeGray() {
    green = red;
    blue = red;
  }
}