diff --git a/hangman/game.py b/hangman/game.py
index ddd76e6..577fd6e 100644
--- a/hangman/game.py
+++ b/hangman/game.py
@@ -1,23 +1,87 @@
 from .exceptions import *
+import random
 
 # Complete with your own, just for fun :)
-LIST_OF_WORDS = []
+LIST_OF_WORDS = ['cookies', 'cream', 'love', 'vinegar']
 
 
 def _get_random_word(list_of_words):
-    pass
+    if list_of_words == []:
+        raise InvalidListOfWordsException
+    else:
+        return random.choice(list_of_words)
 
 
 def _mask_word(word):
-    pass
+    if word == "":
+        raise InvalidWordException
+    else:
+        return len(word)*"*"
 
 
+def find_substring(string, substring):
+    """ 
+    Returns list of indices where substring begins in string
+    >>> find_substring('r', "rmotr")
+    [0, 4]
+    """
+    indices = []
+    index = -1  # Begin at -1 so index + 1 is 0
+    while True: 
+        # Find next index of substring, by starting search from index + 1
+        index = string.find(substring, index + 1)
+        if index == -1:  
+            break  # All occurrences have been found
+        indices.append(index)
+    return indices
+
 def _uncover_word(answer_word, masked_word, character):
-    pass
+    if character == "" or len(character) > 1 :
+        raise InvalidGuessedLetterException(Exception)
+    if len(masked_word) != len(answer_word):
+        raise InvalidWordException
+    if answer_word =="" or masked_word =="" :
+        raise InvalidWordException
+    #convert answer_word and character to lower case    
+    lower_character = str.lower(character)
+    lower_answer = str.lower(answer_word)
+    if lower_character not in lower_answer:
+        return masked_word  
+    #loop through list of indices of answer_word to replace characters
+    if lower_character in lower_answer:
+      indices=find_substring(lower_answer, lower_character)
+      for index in indices:
+        masked_word = masked_word[:index] + lower_character + masked_word[index + 1:]
+    return masked_word
+
 
 
 def guess_letter(game, letter):
-    pass
+
+    if game['remaining_misses']==0 or game['answer_word'] == game['masked_word']:
+        raise GameFinishedException
+    else:
+        #make game case insensitive by converting all strings to lower case
+        letter = str.lower(letter)
+        game['answer_word'] = str.lower(game['answer_word'])
+    
+        game['masked_word'] = _uncover_word(game['answer_word'], game['masked_word'], letter)
+    
+        if game['answer_word'] != game['masked_word']: 
+            game['previous_guesses'] += letter  
+    
+        if letter not in game ['answer_word']:
+            game['remaining_misses'] -= 1
+    
+        if game['remaining_misses']==0:
+            raise GameLostException 
+    
+        if game['answer_word'] == game['masked_word']:
+            raise GameWonException
+        
+        return game 
+    
+    
 
 
 def start_new_game(list_of_words=None, number_of_guesses=5):
diff --git a/one.txt b/one.txt
new file mode 100644
index 0000000..f3fd43f
--- /dev/null
+++ b/one.txt
@@ -0,0 +1,2 @@
+argparse==1.2.1
+wsgiref==0.1.2