[false, false, false, false, false],

    [false, false, false, false, false],

    [true, false, true, false, true],

    [false, false, false, false, false],

    [false, false, false, false, false]

  ];

function setup() {

  createCanvas(400, 400);

  stroke(255, 0, 0);

}

​

function draw() {

  drawGrid();

}

function mousePressed() {

  let col = int(mouseX / 80);

  let row = int(mouseY / 80);

  flipLight(row,col);

  if (isValid(row - 1, col) === true){

    flipLight(row - 1, col);

  }

}

function flipLight(r, c){

  /* your code here */

  grid[r][c] = !grid[r][c];

}

function isValid(r, c){

  /* your code here */

}

function drawGrid(){

  for (var r = 0; r < grid.length; r++)

    for (var c = 0; c < grid[r].length; c++) {

      let x = c * 80;

      let y = r * 80;

      if (grid[r][c] === false) 

        fill(0);

      else 

        fill(255);

      rect(x, y, 80, 80);

    }

}