diff --git a/webgames/__main__.py b/webgames/__main__.py
index 3ba2cf6..31a100e 100644
--- a/webgames/__main__.py
+++ b/webgames/__main__.py
@@ -1,7 +1,7 @@
 import sys
 import json
 from uuid import UUID
-from datetime import datetime
+from datetime import datetime, UTC
 
 import jinja2
 from bottle import Bottle, abort, request, redirect, static_file
@@ -14,7 +14,12 @@ from webgames.game import GameState
 
 
 app = Bottle()
-app.jinja_env = jinja2.Environment(loader=jinja2.FileSystemLoader('templates'))
+app.jinja_env = jinja2.Environment(
+    loader=jinja2.FileSystemLoader('templates'),
+    extensions=[
+        'jinja2.ext.loopcontrols'
+    ]
+)
 
 
 @app.get('/')
@@ -129,7 +134,7 @@ def get_player_game_play(player_id: str, game_id: str):
     game = api.get_game(gameid)
     if game.state == GameState.LOBBY:
         game.begin({}, baseurl=f'{urlbase}/')
-    duration = str(datetime.utcnow() - game.start)
+    duration = str(datetime.now(UTC) - game.start)
     return game.render(app.jinja_env, player, duration)
 
 
@@ -144,7 +149,7 @@ def post_player_game_play(player_id: str, game_id: str):
         game.begin(options=request.forms, urlbase=f'{urlbase}/')
     else:
         game.process_action(playerid, request.forms)
-    duration = str(datetime.utcnow() - game.start)
+    duration = str(datetime.now(UTC) - game.start)
     return game.render(app.jinja_env, player, duration)
 
 #@app.error(404)
diff --git a/webgames/game.py b/webgames/game.py
index a7502d1..2b1dd05 100644
--- a/webgames/game.py
+++ b/webgames/game.py
@@ -2,7 +2,7 @@ from typing import Any, Dict, List
 
 from enum import Enum
 from uuid import uuid4, UUID
-from datetime import datetime
+from datetime import datetime, UTC
 
 from webgames.puzzle import Puzzle
 
@@ -10,6 +10,7 @@ from webgames.sudoku_puzzle import Sudoku
 from webgames.set_puzzle import SetPuzzle
 from webgames.carcassonne import Carcassonne
 from webgames.go import GoPuzzle
+from webgames.mastermind import Mastermind
 from webgames.player import Player
 from webgames.human import HumanID
 
@@ -47,7 +48,7 @@ class Game:
     def begin(self, options, urlbase) -> None:
         if self._state != GameState.LOBBY:
             raise RuntimeError(f'Can\'t start a game in {self._state} state')
-        self._start = datetime.utcnow()
+        self._start = datetime.now(UTC)
         self._state = GameState.RUNNING
         self._puzzle.begin(options, urlbase)
 
@@ -55,8 +56,8 @@ class Game:
         if self._state == GameState.FINISHED:
             raise RuntimeError(f'Can\'t start a game in {self._state} state')
         if not self._start:
-            self._start = datetime.utcnow()
-        self._end = datetime.utcnow()
+            self._start = datetime.now(UTC)
+        self._end = datetime.now(UTC)
         self._state = GameState.FINISHED
 
     def process_action(self, player: UUID, action) -> None:
diff --git a/webgames/sudoku_puzzle.py b/webgames/sudoku_puzzle.py
index 6351ec4..7b805d1 100644
--- a/webgames/sudoku_puzzle.py
+++ b/webgames/sudoku_puzzle.py
@@ -1,6 +1,7 @@
 from typing import Any, Dict
 
 from uuid import UUID
+from datetime import datetime, UTC
 
 from sudokugen.solver import solve, NoSolution
 from sudoku_manager import Sudoku as SudokuManager
@@ -120,13 +121,13 @@ class SudokuPuzzle(Puzzle):
             value = None
         else:
             value = int(v)
-        
+
         puzzle = self._puzzles[player]
         if puzzle.solved:
             raise RuntimeError(f'Can\'t process a game action for a solved puzzle')
         puzzle.process_action(action)
         if puzzle.solved:
-            duration = datetime.utcnow() - self._start
+            duration = datetime.now(UTC) - self._start
             self._scores.append({
                 'player': player,
                 'duration': duration