var board = document
    .getElementsByClassName("memory-test")[0]
    .firstChild
    .children[1]
    .firstChild
    .children[1]
    .firstChild;

function triggerMouseEvent(node, eventType) {
  var clickEvent = document.createEvent('MouseEvents');
  clickEvent.initEvent(eventType, true, true);
  node.dispatchEvent(clickEvent);
}

function click(node) {
  triggerMouseEvent(node, "mousedown");
  triggerMouseEvent(node, "mouseup");
  triggerMouseEvent(node, "click");
}

var callback = (mutationList, observer) => {
  // check if the mutation is not the board changing size
  if (mutationList.length < board.childElementCount ** 2) {
    mutationList.forEach((mut) => {
      click(mut.target);
    })
  }
}
var ob = new MutationObserver(callback)

ob.observe(board, {
    attributes: true,
    childList: true,
    subtree: true,
  });