(() => {
    function CountDown() {
      var count = 4,
      tmID,
      hit = Math.floor(Math.random()*10+1);
      areas = document.querySelectorAll("div"),
      button = document.getElementById("start"),
      infobox = document.getElementById("result");
      function countDown() {
          if (--count == 0) {
              infobox.innerHTML = "失敗…";
              infobox.setAttribute("class", "failure")
              for (let i of areas) {
                  if (i.textContent == hit) {
                      i.removeEventListener("click", stopCountDown, false);
                  }
              }
          } else {
              infobox.innerHTML = count + "秒前";
              tmID = setTimeout(countDown, 1000);
          }
      }
      function startCountDown() {
          tmID = setTimeout(countDown, 1000);
          button.removeEventListener("click", startCountDown, false);
          for (let i of areas) {
              if (i.textContent == hit) {
                  i.addEventListener("click", stopCountDown, false);
              }
          }
      }
      function stopCountDown() {
          clearTimeout(tmID);
          infobox.innerHTML = "成功!!";
          infobox.setAttribute("class", "success");
          areas.removeEventListener("click", stopCountDown, false);
      }
      button.addEventListener("click", startCountDown, false);
    }
    document.addEventListener("DOMContentLoaded", CountDown, false);
  })();