diff --git a/countdown.js b/countdown.js
new file mode 100644
index 0000000..c5b9184
--- /dev/null
+++ b/countdown.js
@@ -0,0 +1,23 @@
+function CountDown() {
+    var count = 4, tmID,infobox = document.getElementById("start"),seiko = document.getElementById("atari"),kekka = document.getElementById("info");
+    function countDown() {
+	if (--count == 0) {
+	    kekka.innerHTML = "ぼかーん";
+	} else {
+	    kekka.innerHTML = count + "秒前";
+	    tmID = setTimeout(countDown, 1000);
+	}
+    }
+    function startCountDown() {
+	tmID = setTimeout(countDown, 1000);
+	infobox.removeEventListener("click", startCountDown, false);
+	seiko.addEventListener("click", stopCountDown, false);
+    }
+    function stopCountDown() {
+	clearTimeout(tmID);
+	seiko.innerHTML = "正解!よくわかったね";
+	seiko.removeEventListener("click", stopCountDown, false);
+    }
+    infobox.addEventListener("click", startCountDown, false);
+};
+document.addEventListener("DOMContentLoaded", CountDown, false);