diff --git a/Course3/Lab4/validations.py b/Course3/Lab4/validations.py
index b18de65a2e..79d493eb04 100644
--- a/Course3/Lab4/validations.py
+++ b/Course3/Lab4/validations.py
@@ -2,23 +2,68 @@
 
 import re
 
+
+
 def validate_user(username, minlen):
+
     """Checks if the received username matches the required conditions."""
+
     if type(username) != str:
+
         raise TypeError("username must be a string")
+
     if minlen < 1:
+
         raise ValueError("minlen must be at least 1")
-    
+
+
+
     # Usernames can't be shorter than minlen
+
     if len(username) < minlen:
+
         return False
+
+
+
     # Usernames can only use letters, numbers, dots and underscores
-    if not re.match('^[a-z0-9._]*$', username):
+
+    if not re.match(r'^[a-zA-Z0-9._]*$', username):
+
         return False
+
+
+
     # Usernames can't begin with a number
+
     if username[0].isnumeric():
+
+        return False
+
+
+
+    # Usernames can't begin with . or _
+
+    if username[0] in ['.', '_']:
+
         return False
+
+
+
     return True
 
 
 
+
+
+# Test cases
+
+print(validate_user("blue.kale", 3))    # True
+
+print(validate_user(".blue.kale", 3))   # False
+
+print(validate_user("red_quinoa", 4))   # True
+
+print(validate_user("_red_quinoa", 4))  # False
+
+