for (var b = 0; b < allBoxes.length; b++) {
    allBoxes[b].onclick = function() {

        this.innerHTML = "X";
        this.style.color = "#fe7bff";

  // Add some competition
        var ai = Math.floor((Math.random() * allBoxes.length) );
        console.log(ai); // Pattern of errors at certain indices?
        if (allBoxes[ai] === "") {
          allBoxes[ai].innerHTML = "O";
          allBoxes[ai].style.color = "#ffdb00";
        } else {
          "Y"; // When is "else" executed?
          allBoxes[ai].style.color = "#ffdb00";
        }