diff --git a/src/game/typing/lib/extract_word_manager.js b/src/game/typing/lib/extract_word_manager.js
index 17645f8..75585b0 100644
--- a/src/game/typing/lib/extract_word_manager.js
+++ b/src/game/typing/lib/extract_word_manager.js
@@ -1,8 +1,8 @@
 function ExtractWordManager() {
-	this.init();
+	this.initVariables();
 }
 
-ExtractWordManager.prototype.init = function() {
+ExtractWordManager.prototype.initVariables = function() {
 	this.koreanWordList = [];
 	this.koreanWordList[0] = koreanBasicWordList;
 	this.koreanWordList[1] = koreanLeftUpperWordList;
@@ -27,29 +27,74 @@ ExtractWordManager.prototype.init = function() {
 }
 
 
-ExtractWordManager.prototype.getWord = function(wordLevel, wordLength) {
-	if(isKoreanTypingApp())
-		return this.getKoreanWord(wordLevel, wordLength);
-	else
-		return this.getEnglishWord(wordLevel, wordLength);
+ExtractWordManager.prototype.isValidWordForLevel = function(word, difficultyForLevel) {
+	// console.log("word : " + word);
+	// console.log("difficultyForLevel : " + difficultyForLevel);
+	if(word == "")
+		return false;
+
+	var wordLength = word.length;
+
+	if(difficultyForLevel == ExtractWordManager.DIFFICULTY_EASY) {
+		var maxWordLength = 0;
+
+		if(isKoreanTypingApp()) {
+			maxWordLength = ExtractWordManager.DIFFICULTY_EASY_KOREAN_WORD_LENGTH;
+		} else {
+			maxWordLength = ExtractWordManager.DIFFICULTY_EASY_ENGLISH_WORD_LENGTH;
+		}
+
+		if(wordLength <= maxWordLength)
+			return true;
+		else
+			return false;
+	} else {
+		var minWordLength = 0;
+
+		if(isKoreanTypingApp()) {
+			minWordLength = ExtractWordManager.DIFFICULTY_EASY_KOREAN_WORD_LENGTH;
+		} else {
+			minWordLength = ExtractWordManager.DIFFICULTY_EASY_ENGLISH_WORD_LENGTH;
+		}
+
+		if(wordLength > minWordLength)
+			return true;
+		else
+			return false;
+	}
+
+}
+
+ExtractWordManager.prototype.getWord = function(wordLevel, difficultyForLevel) {
+	// console.log("wordLevel : " + wordLevel);
+	// console.log("difficultyForLevel : " + difficultyForLevel);
+	var word = "";
+	var wordLength = 0;
+	var count = 0;
+	while(word == "" || !this.isValidWordForLevel(word, difficultyForLevel)) {
+		if(isKoreanTypingApp())
+			word = this.getRandomWord(this.koreanWordList[wordLevel]);
+		else
+			word = this.getRandomWord(this.englishWordList[wordLevel]);
+
+		// console.log(word);
+		count++;
+		if(count > 100) {
+			console.log("warning : infinity loop!!!");
+			return "???";
+		}
+	}
+	return word;
 }
 
 ExtractWordManager.prototype.getRandomWord = function(wordList) {
-	var index = Math.floor(Math.random() * wordList.length);
-	return wordList[index];
+	var randomIndex = Math.floor(Math.random() * wordList.length);
+	return wordList[randomIndex];
 }
 
 
-ExtractWordManager.prototype.getKoreanWord = function(wordLevel, wordLength) {
-	return this.getRandomWord(this.koreanWordList[wordLevel]);
-}
-
-ExtractWordManager.prototype.getEnglishWord = function(wordLevel, wordLength) {
-	return this.getRandomWord(this.englishWordList[wordLevel]);
-}
-
 ExtractWordManager.prototype.removeWord = function(wordLevel, word) {
-	console.log("remove : " + wordLevel + ", " + word);
+	// console.log("remove : " + wordLevel + ", " + word);
 }
 
 
@@ -183,3 +228,12 @@ ExtractWordManager.ENGLISH_LETTER_RIGHT = [
 	"h", "j", "k", "l",
 	"n", "m"
 ];
+
+
+
+
+ExtractWordManager.DIFFICULTY_EASY		= 0;
+ExtractWordManager.DIFFICULTY_HARD		= 1
+
+ExtractWordManager.DIFFICULTY_EASY_KOREAN_WORD_LENGTH	= 2;
+ExtractWordManager.DIFFICULTY_EASY_ENGLISH_WORD_LENGTH	= 3;
\ No newline at end of file
diff --git a/src/game/typing/word_flyingsaucer/flyingsaucer.js b/src/game/typing/word_flyingsaucer/flyingsaucer.js
index 0cbfad0..69d6458 100644
--- a/src/game/typing/word_flyingsaucer/flyingsaucer.js
+++ b/src/game/typing/word_flyingsaucer/flyingsaucer.js
@@ -48,7 +48,7 @@ function FlyingSaucer(lineIndex) {
 FlyingSaucer.prototype.initVariables = function() {
 	this.isActivated = false;
 	this.wordLevel = 0;
-	this.wordLength = 0;
+	this.difficultyForLevel = 0;
 	this.standardScore = 0;
 	this.speed = FlyingSaucer.DEFAULT_SPEED;
 	this.jetStatus = FlyingSaucer.JET_STATUS_HIGH;
@@ -190,8 +190,12 @@ FlyingSaucer.prototype.moveInitialPos = function() {
 
 FlyingSaucer.prototype.startAttack = function() {
 	this.wordLevel = this.gameLevelManager.getWordLevel();
-	this.wordLength = this.gameLevelManager.getWordLength(this.wordLevel);
-	this.word = this.extractWordManager.getWord(this.wordLevel, this.wordLength);
+	this.difficultyForLevel = this.gameLevelManager.getDifficultyForLevel();
+	// console.log("====");
+	// console.log("this.wordLevel : " + this.wordLevel);
+	// console.log("this.difficultyForLevel : " + this.difficultyForLevel);
+	this.word = this.extractWordManager.getWord(this.wordLevel, this.difficultyForLevel);
+	// console.log("this.word : " + this.word);
 	this.setWord(this.word);
 	this.standardScore = this.gameLevelManager.getStandardScore(this.wordLevel, this.speed);
 	// console.log(this.standardScore);
diff --git a/src/game/typing/word_flyingsaucer/game_level_manager.js b/src/game/typing/word_flyingsaucer/game_level_manager.js
index 4d186c2..495ea46 100644
--- a/src/game/typing/word_flyingsaucer/game_level_manager.js
+++ b/src/game/typing/word_flyingsaucer/game_level_manager.js
@@ -1,15 +1,19 @@
 function GameLevelManager() {
 	this.wordLevel = 0;
-	this.wordLength = GameLevelManager.MIN_WORD_LENGTH;
-	this.clearPoint = 0.1;
+
+	this.clearedWordCountForLevel = [0, 0, 0, 0, 0];
+
+	this.difficultyForLevelList = [];
+	for(var i = 0; i < GameLevelManager.MAX_WORD_LEVEL; i++)
+		this.difficultyForLevelList[i] = ExtractWordManager.DIFFICULTY_EASY;
 }
 
 GameLevelManager.prototype.getWordLevel = function() {
 	return this.wordLevel;
 }
 
-GameLevelManager.prototype.getWordLength = function() {
-	return this.wordLength;
+GameLevelManager.prototype.getDifficultyForLevel = function() {
+	return this.difficultyForLevelList[this.wordLevel];
 }
 
 GameLevelManager.prototype.getStandardScore = function(wordLevel, speed) {
@@ -18,31 +22,58 @@ GameLevelManager.prototype.getStandardScore = function(wordLevel, speed) {
 
 
 GameLevelManager.prototype.clearWord = function(wordLevel, landingRatio) {
-	console.log("wordLevel : " + wordLevel);
-	console.log("landingRatio : " + landingRatio);
-	if(this.wordLevel == GameLevelManager.MAX_KOR_WORD_LEVEL || wordLevel < this.wordLevel) {
-		this.wordLength++;
+	// console.log("====");
+	// for(var i = 0; i < this.difficultyForLevelList.length; i++) {
+	// 	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);
 		return;
 	}
 
-	if(landingRatio < GameLevelManager.LEVEL_UP_LANDING_RATIO) {
-		this.wordLength++;
+	if(wordLevel < this.wordLevel || landingRatio < GameLevelManager.LEVEL_UP_LANDING_RATIO) {
+		this.increaseClearedWordCountForLevel(wordLevel);
 		return;
 	}
 
 	this.goNextWordLevel();
 }
 
+GameLevelManager.prototype.increaseClearedWordCountForLevel = function(wordLevel) {
+	this.clearedWordCountForLevel[wordLevel]++;
+
+	var difficulty = this.difficultyForLevelList[wordLevel];
+	var clearedWordCount = this.clearedWordCountForLevel[wordLevel];
+	var clearedWordCountForNextLevel = GameLevelManager.CLEARED_WORD_COUNT_FOR_NEXT_LEVEL[difficulty];
+
+	// console.log("=============");
+	// console.log("difficulty : " + difficulty);
+	// console.log("clearedWordCount : " + clearedWordCount);
+	// console.log("clearedWordCountForNextLevel : " + clearedWordCountForNextLevel);
+
+	if(difficulty == ExtractWordManager.DIFFICULTY_EASY
+		&& clearedWordCount >= clearedWordCountForNextLevel) {
+
+		this.difficultyForLevelList[wordLevel] = ExtractWordManager.DIFFICULTY_HARD;
+		// console.log("level[" + wordLevel + "] : difficulty -> HARD");
+	}
+}
+
 GameLevelManager.prototype.goNextWordLevel = function() {
-	console.log("goNextWordLevel");
 	this.wordLevel++;
-	this.wordLength = 1;
+	console.log("goNextWordLevel to " + this.wordLevel);
 }
 
 
-GameLevelManager.LEVEL_UP_LANDING_RATIO			= 0.7;
+GameLevelManager.LEVEL_UP_LANDING_RATIO			= 0.9;
 GameLevelManager.WARNING_LANDING_RATIO			= 0.1;
 
-GameLevelManager.MAX_KOR_WORD_LEVEL		= 5;
+GameLevelManager.MAX_WORD_LEVEL		= 6;
 
-GameLevelManager.MIN_WORD_LENGTH		= 2;
\ No newline at end of file
+GameLevelManager.CLEARED_WORD_COUNT_FOR_NEXT_LEVEL		= [5, 6, 7, 8, 9, 10];
+
+GameLevelManager.KOREAN_WORD_LENGTH		= [2, 3];
+GameLevelManager.ENGLISH_WORD_LENGTH	= [3, 6];;
\ No newline at end of file
diff --git a/src/web/client/word_flyingsaucer.html b/src/web/client/word_flyingsaucer.html
index af8b658..2d2d559 100644
--- a/src/web/client/word_flyingsaucer.html
+++ b/src/web/client/word_flyingsaucer.html
@@ -74,7 +74,7 @@
 		<script src="../../game/typing/word_list/korean_right_lower.js"></script>
 		<script src="../../game/typing/word_list/korean_left_upper_double.js"></script>
 		<script src="../../game/typing/word_list/korean_right_upper_double.js"></script>
-		<script src="../../game/typing/word_list/korean_word.js"></script>
+		<!-- <script src="../../game/typing/word_list/korean_word.js"></script> -->
 
 		<script src="../../game/typing/word_list/english_basic.js"></script>
 		<script src="../../game/typing/word_list/english_left_lower.js"></script>
@@ -82,7 +82,7 @@
 		<script src="../../game/typing/word_list/english_right_lower.js"></script>
 		<script src="../../game/typing/word_list/english_right_upper.js"></script>
 		<script src="../../game/typing/word_list/english_second_finger.js"></script>
-		<script src="../../game/typing/word_list/english_word.js"></script>
+		<!-- <script src="../../game/typing/word_list/english_word.js"></script> -->
 
 		<!-- Shoot down! flyingsaucer : source files -->
 		<script src="../../game/typing/lib/typing_content_bg.js"></script>