diff --git a/src/dndbuster/timer.py b/src/dndbuster/timer.py
index ceae7e2..92f538c 100644
--- a/src/dndbuster/timer.py
+++ b/src/dndbuster/timer.py
@@ -1,58 +1,81 @@
 import time
 
 
-class Timer:
+class SimpleTimer:
     def __init__(self) -> None:
-        self.start_seconds: float | None= None
-        self.pause_timer: Timer | None = None
+        self.start_seconds: float = 0
+        self.started = False
 
     def start(self) -> None:
         """
         Start time measurement
         """
-        self.start_seconds = self.current_time()
-
+        if not self.started:
+            self.start_seconds = self.current_time()
+            self.started = True
 
     def is_started(self) -> bool:
         """
         :return: Weather time measurement has been started.
         """
-        return self.start_seconds is not None
+        return self.started
+
+    def read(self) -> float:
+        """
+        Return measured time in seconds.
+        """
+        if self.started:
+            end_seconds = self.current_time()
+            delta = end_seconds - self.start_seconds
+            return delta
+        else:
+            raise ValueError(f'{self.__class__.__name__} has to be started before there is a time measurement.')
+
+    def reset(self) -> None:
+        self.started = False
+
+    @classmethod
+    def current_time(cls):
+        return time.time()
+
+
+class Timer(SimpleTimer):
+    def __init__(self) -> None:
+        super().__init__()
+        self.pause_timer = SimpleTimer()
 
     def pause(self) -> None:
         """
         Pause time measurement.
         """
-        self.pause_timer = Timer()
         self.pause_timer.start()
 
     def is_paused(self) -> bool:
         """
         :return: Weather time measurement is paused.
         """
-        return self.pause_timer is not None
+        return self.pause_timer.is_started()
 
     def resume(self) -> None:
         """
         Resumes time measurement.
         """
-        if self.pause_timer:
+        if self.is_paused():
             pause_delta = self.pause_timer.read()
             self.start_seconds += pause_delta
-            self.pause_timer = None
+            self.pause_timer.reset()
 
     def read(self) -> float:
         """
         Return measured time in seconds.
         """
-        end_seconds = self.current_time()
-        delta = end_seconds - self.start_seconds
+        delta = SimpleTimer.read(self)
 
         if self.is_paused():
             delta -= self.pause_timer.read()
 
         return delta
 
-    @classmethod
-    def current_time(cls):
-        return time.time()
+    def reset(self) -> None:
+        SimpleTimer.reset(self)
+        self.pause_timer.reset()