diff --git a/src/game/lib/text/score_text.js b/src/game/lib/text/score_text.js
index 3632d32..cd6d7f9 100644
--- a/src/game/lib/text/score_text.js
+++ b/src/game/lib/text/score_text.js
@@ -9,6 +9,11 @@ function ScoreText(x, y, score) {
 	else if(scoreValue < 0)
 		Phaser.Text.call(this, game, x, y, NumberUtil.numberWithCommas(score), ScoreText.DEFAULT_TEXT_FONT);
 
+	if(this == undefined) {
+		this.destroy();
+		return;
+	}
+
 	this.anchor.set(0.5);
 	this.inputEnabled = false;
 
diff --git a/src/game/typing/word_flyingsaucer/flyingsaucer.js b/src/game/typing/word_flyingsaucer/flyingsaucer.js
index 69d6458..5ae505c 100644
--- a/src/game/typing/word_flyingsaucer/flyingsaucer.js
+++ b/src/game/typing/word_flyingsaucer/flyingsaucer.js
@@ -190,7 +190,7 @@ FlyingSaucer.prototype.moveInitialPos = function() {
 
 FlyingSaucer.prototype.startAttack = function() {
 	this.wordLevel = this.gameLevelManager.getWordLevel();
-	this.difficultyForLevel = this.gameLevelManager.getDifficultyForLevel();
+	this.difficultyForLevel = this.gameLevelManager.getDifficultyForLevel(this.wordLevel);
 	// console.log("====");
 	// console.log("this.wordLevel : " + this.wordLevel);
 	// console.log("this.difficultyForLevel : " + this.difficultyForLevel);
@@ -205,6 +205,9 @@ FlyingSaucer.prototype.startAttack = function() {
 }
 
 FlyingSaucer.prototype.checkInputText = function(inputText) {
+	if(!this.isActivated)
+		return;
+
 	// console.log("inputText : " + inputText);
 	// console.log("this.wordText : " + this.wordText);
 	this.wordText.clearColors();
@@ -237,6 +240,9 @@ FlyingSaucer.prototype.getLandingRatio = function(inputText) {
 }
 
 FlyingSaucer.prototype.checkWord = function(inputText) {
+	if(!this.isActivated)
+		return;
+
 	// console.log("inputText : " + inputText);
 	// console.log("this.wordText : " + this.wordText);
 
@@ -260,7 +266,8 @@ FlyingSaucer.prototype.explode = function(inputText) {
 	this.explodeEmitter.y = this.y;
 	this.explodeEmitter.start(true, 1000, null, 100);
 
-	this.timerEvent = game.time.events.add(Phaser.Timer.SECOND, this.startAttack, this);
+	var randomDelayTime = Phaser.Timer.SECOND + Math.random() * Phaser.Timer.SECOND;
+	this.timerEvent = game.time.events.add(randomDelayTime, this.startAttack, this);
 }
 
 FlyingSaucer.prototype.plusScore = function(inputText) {
@@ -277,6 +284,9 @@ FlyingSaucer.prototype.crash = function() {
 }
 
 FlyingSaucer.prototype.destroy = function() {
+	if(this.timerEvent)
+		game.time.events.remove(this.timerEvent);
+
 	this.setActive(false);
 	this.setWord("");
 }
diff --git a/src/game/typing/word_flyingsaucer/game_level_manager.js b/src/game/typing/word_flyingsaucer/game_level_manager.js
index 495ea46..3c7b2a4 100644
--- a/src/game/typing/word_flyingsaucer/game_level_manager.js
+++ b/src/game/typing/word_flyingsaucer/game_level_manager.js
@@ -9,11 +9,12 @@ function GameLevelManager() {
 }
 
 GameLevelManager.prototype.getWordLevel = function() {
-	return this.wordLevel;
+	var randomLevel = Math.floor(Math.random() * (this.wordLevel + 1));
+	return randomLevel;
 }
 
-GameLevelManager.prototype.getDifficultyForLevel = function() {
-	return this.difficultyForLevelList[this.wordLevel];
+GameLevelManager.prototype.getDifficultyForLevel = function(wordLevel) {
+	return this.difficultyForLevelList[wordLevel];
 }
 
 GameLevelManager.prototype.getStandardScore = function(wordLevel, speed) {
@@ -27,15 +28,23 @@ GameLevelManager.prototype.clearWord = function(wordLevel, landingRatio) {
 	// 	console.log("difficultyForLevelList[" + i + "] : " + this.difficultyForLevelList[i]);
 	// }
 
-	// console.log("wordLevel : " + wordLevel);
-	// console.log("landingRatio : " + landingRatio);
-	if(this.wordLevel == GameLevelManager.MAX_WORD_LEVEL || wordLevel < this.wordLevel) {
-		this.increaseClearedWordCountForLevel(wordLevel);
+	console.log("wordLevel : " + wordLevel);
+	console.log("landingRatio : " + landingRatio);
+
+	this.increaseClearedWordCountForLevel(wordLevel);
+
+	if(this.wordLevel == GameLevelManager.MAX_WORD_LEVEL) {
+		console.log("*** no more higher word level");
 		return;
 	}
 
-	if(wordLevel < this.wordLevel || landingRatio < GameLevelManager.LEVEL_UP_LANDING_RATIO) {
-		this.increaseClearedWordCountForLevel(wordLevel);
+	if(wordLevel < this.wordLevel) {
+		console.log("*** already goNextLevel");
+		return;
+	}
+
+	if(landingRatio < GameLevelManager.LEVEL_UP_LANDING_RATIO) {
+		console.log("*** not enough ratio");
 		return;
 	}
 
@@ -43,7 +52,12 @@ GameLevelManager.prototype.clearWord = function(wordLevel, landingRatio) {
 }
 
 GameLevelManager.prototype.increaseClearedWordCountForLevel = function(wordLevel) {
-	this.clearedWordCountForLevel[wordLevel]++;
+	this.clearedWordCountForLevel[wordLevel] += 1;
+
+	// console.log("====");
+	// for(var i = 0; i < this.clearedWordCountForLevel.length; i++) {
+	// 	console.log("clearedWordCountForLevel[" + i + "] : " + this.clearedWordCountForLevel[i]);
+	// }
 
 	var difficulty = this.difficultyForLevelList[wordLevel];
 	var clearedWordCount = this.clearedWordCountForLevel[wordLevel];
@@ -58,7 +72,7 @@ GameLevelManager.prototype.increaseClearedWordCountForLevel = function(wordLevel
 		&& clearedWordCount >= clearedWordCountForNextLevel) {
 
 		this.difficultyForLevelList[wordLevel] = ExtractWordManager.DIFFICULTY_HARD;
-		// console.log("level[" + wordLevel + "] : difficulty -> HARD");
+		console.log("level[" + wordLevel + "] : difficulty -> HARD");
 	}
 }
 
@@ -68,7 +82,7 @@ GameLevelManager.prototype.goNextWordLevel = function() {
 }
 
 
-GameLevelManager.LEVEL_UP_LANDING_RATIO			= 0.9;
+GameLevelManager.LEVEL_UP_LANDING_RATIO			= 0.7;
 GameLevelManager.WARNING_LANDING_RATIO			= 0.1;
 
 GameLevelManager.MAX_WORD_LEVEL		= 6;