diff --git a/generals/agents/agent.py b/generals/agents/agent.py
index 84453ad..06842d3 100644
--- a/generals/agents/agent.py
+++ b/generals/agents/agent.py
@@ -1,7 +1,7 @@
-from abc import abstractmethod
+from abc import ABC, abstractmethod
 
 
-class Agent:
+class Agent(ABC):
     """
     Base class for all agents.
     """
diff --git a/generals/gui/event_handler.py b/generals/gui/event_handler.py
index 4c6d1f1..0fb29e2 100644
--- a/generals/gui/event_handler.py
+++ b/generals/gui/event_handler.py
@@ -1,7 +1,7 @@
 import pygame
 from enum import Enum
 from pygame.event import Event
-from abc import abstractmethod
+from abc import ABC, abstractmethod
 
 from .properties import Properties
 from generals.core import config as c
@@ -45,7 +45,7 @@ def __init__(self):
         super().__init__()
 
 
-class EventHandler:
+class EventHandler(ABC):
     def __init__(self, properties: Properties):
         """
         Initialize the event handler.
@@ -56,6 +56,11 @@ def __init__(self, properties: Properties):
         self.properties = properties
         self.mode = properties.mode
 
+    @property
+    @abstractmethod
+    def command(self) -> Command:
+        raise NotImplementedError
+
     def handle_events(self) -> Command:
         """
         Handle pygame GUI events
@@ -105,7 +110,11 @@ def handle_mouse_event(self):
 class ReplayEventHandler(EventHandler):
     def __init__(self, properties: Properties):
         super().__init__(properties)
-        self.command = ReplayCommand()
+        self._command = ReplayCommand()
+
+    @property
+    def command(self) -> ReplayCommand:
+        return self._command
 
     def handle_key_event(self, event: Event) -> ReplayCommand:
         match event.key:
@@ -135,7 +144,11 @@ def handle_mouse_event(self) -> None:
 class GameEventHandler(EventHandler):
     def __init__(self, properties: Properties):
         super().__init__(properties)
-        self.command = GameCommand()
+        self._command = GameCommand()
+
+    @property
+    def command(self) -> GameCommand:
+        return self._command
 
     def handle_key_event(self, event: Event) -> GameCommand:
         raise NotImplementedError
@@ -147,7 +160,11 @@ def handle_mouse_event(self) -> None:
 class TrainEventHandler(EventHandler):
     def __init__(self, properties: Properties):
         super().__init__(properties)
-        self.command = TrainCommand()
+        self._command = TrainCommand()
+
+    @property
+    def command(self) -> TrainCommand:
+        return self._command
 
     def handle_key_event(self, event: Event) -> TrainCommand:
         if event.key == Keybindings.Q.value:
diff --git a/generals/gui/gui.py b/generals/gui/gui.py
index 531fda8..40e3c92 100644
--- a/generals/gui/gui.py
+++ b/generals/gui/gui.py
@@ -3,7 +3,7 @@
 
 from generals.core.game import Game
 from .properties import Properties
-from .event_handler import TrainEventHandler, GameEventHandler, ReplayEventHandler
+from .event_handler import TrainEventHandler, GameEventHandler, ReplayEventHandler, ReplayCommand
 from .rendering import Renderer
 
 
@@ -37,7 +37,7 @@ def tick(self, fps=None):
         command = handler.handle_events()
         if command.quit:
             quit()
-        if self.properties.mode == "replay":
+        if isinstance(command, ReplayCommand):
             self.properties.update_speed(command.speed_change)
             if command.frame_change != 0 or command.restart:
                 self.properties.paused = True