2D grid array question

Processing Coding Questions
16

This what I’ve got now. The entire grid increments as a whole. The clue: [x+1][y], I can’t figure out how (where) to add the +1 / -1 to cell index so as to move individual cells.

I think(?) something sh’d be added to the void keyReleased() code block, but am not sure what.

// 2D Grid Array of Button objects
Button [][] myButtons;

// Number of columns and rows in the grid
int num = 10;
int cols = num, rows = cols;

color background = color (random(255), random(255), random(255));

void setup() {
  size(500, 500);

  int x = (width/num)/2, y = x;

  myButtons = new Button[cols][rows];
  for (int i = 0; i < cols; i++) {
    for (int j = 0; j < rows; j++) {
      // Initialize each object
      myButtons[i][j] = new Button (x+ i*(width/cols), y+ j*(height/rows), 
        color (random(255), random(255), random(255)), // random colors
        color (random(255), random(255), random(255)), // new random colors when mouseOver
        (width/num));
    }
  }
}

void draw() {

  background(background);


  for (int i = 0; i < cols; i++) {
    for (int j = 0; j < rows; j++) {
      myButtons[i][j].mouseOver();
      myButtons[i][j].display();
    }
  }
}
void keyReleased() {

  for (int i = 0; i < cols; i++) {
    for (int j = 0; j < rows; j++) {
      myButtons[i][j].keyPressed();
    }
  }
}

//////////////////////////////

class Button {
  float x, y;
  color colRect;
  color colRect2;

  float sz;
  boolean off = true; // button starts in OFF position

  Button ( 
    float tempX, float tempY, 
    color tempColor, color tempColor2, float tempSz) {

    x = tempX;
    y = tempY;

    colRect = tempColor;
    colRect2 = tempColor2;

    sz = tempSz;
  }

  void display() {
    if (off) {
      fill (colRect);
      noStroke();
    } else {
      fill (colRect2);
      noStroke();
    }

    rectMode(CENTER);
    rect(x, y, sz, sz);
  }

  void mouseOver() {

    if (mouseX > x - sz/2 && 
      mouseX < x + sz/2 &&
      mouseY > y - sz/2 &&
      mouseY < y + sz/2) {

      off = false;
    } else {
      off = true;
    }
  }

  void keyPressed() {

    if (key == CODED) {
      if (keyCode== UP) {
        y = y+1;
      } else if (keyCode== DOWN) {
        y = y-1;
      } else if (keyCode== LEFT) {
        x = x-1;
      } else if (keyCode== RIGHT) {
        x = x+1;
      }
    }
  }
}