diff --git a/timer.py b/timer.py
index d01d7e7..e626c0f 100755
--- a/timer.py
+++ b/timer.py
@@ -1,23 +1,24 @@
 #!/bin/env python3
 import datetime
-from tkinter import Tk, CENTER, Label
+from tkinter import Tk, CENTER, Label, font
 import click
 import typing as t
 
 DELTA_SECONDS = "+%Ss"
 DELTA_MINUTES = "+%Mm"
 DELTA_HOURS = "+%Hh"
-HOURS = "%H:%M"
+TIME_TODAY = "%H:%M"
 DATETIME_FORMAT = [
     "%Y-%m-%d",
     "%Y-%m-%dT%H:%M:%S",
     "%Y-%m-%d %H:%M:%S",
     "%Y-%m-%d %H:%M",
-    HOURS,
+    TIME_TODAY,
     DELTA_HOURS,
     DELTA_MINUTES,
     DELTA_SECONDS,
 ]
+FONT = "Liberation Sans"
 
 
 class DateTime(click.DateTime):
@@ -36,7 +37,7 @@ class DateTime(click.DateTime):
                     return datetime.datetime.now() + datetime.timedelta(
                         hours=int(value[1:-1])
                     )
-            if format == HOURS:
+            if format == TIME_TODAY:
                 return datetime.datetime.combine(
                     datetime.datetime.now().date(),
                     datetime.datetime.strptime(value, format).time(),
@@ -46,37 +47,89 @@ class DateTime(click.DateTime):
             return None
 
 
-def start_app(end_date):
-    root = Tk()
-    root.geometry("300x100+200+200")
-    root.configure(background="#000")
-    timer_label = Label(root, text="", font=("Arial", -100), fg="#fff", bg="#000")
-    timer_label.pack()
-    timer_label.place(relx=0.5, rely=0.5, anchor=CENTER)
+class Timer:
+    def __init__(self, end_date):
+        self.end_date = end_date
+        self.update()
 
-    def format_delta(t):
-        days, remainder = divmod(t.total_seconds(), 60 * 60 * 24)
+    def update(self):
+        self.delta = self.end_date - datetime.datetime.now()
+
+    def calc_delta(self):
+        days, remainder = divmod(self.delta.total_seconds(), 60 * 60 * 24)
         hours, remainder = divmod(remainder, 3600)
         minutes, seconds = divmod(remainder, 60)
+        return int(days), int(hours), int(minutes), int(seconds)
+
+    @classmethod
+    def get_format(cls, days, hours, minutes, seconds):
         if days == 0:
             if hours == 0:
                 if minutes == 0:
-                    return f"{int(seconds):02d}"
-                return f"{int(minutes):02d}:{int(seconds):02d}"
-            return f"{int(hours):02d}:{int(minutes):02d}:{int(seconds):02d}"
-        return f"{int(days):02d}:{int(hours):02d}:{int(minutes):02d}:{int(seconds):02d}"
+                    return "{seconds:02d}"
+                return "{minutes:02d}:{seconds:02d}"
+            return "{hours:02d}:{minutes:02d}:{seconds:02d}"
+        return "{days:02d}:{hours:02d}:{minutes:02d}:{seconds:02d}"
+
+    def __str__(self):
+        days, hours, minutes, seconds = self.calc_delta()
+        return self.get_format(days, hours, minutes, seconds).format(
+            days=days, hours=hours, minutes=minutes, seconds=seconds
+        )
+
+
+current_size = {
+    "format": Timer.get_format(9, 9, 9, 9),
+    "height": 800,
+    "width": 800,
+}
+
+
+def start_app(end_date):
+    timer = Timer(end_date)
+    root = Tk()
+    root.geometry("300x100+200+200")
+    root.configure(background="#000")
+    font_instance = font.Font(font=(FONT, -100))
+    timer_label = Label(root, text="", font=font_instance, fg="#fff", bg="#000")
+    timer_label.pack()
+    timer_label.place(relx=0.5, rely=0.5, anchor=CENTER)
+    fixed_font_instance = font.Font(font=(FONT, -100))
 
     def resize(_):
-        ratio = root.winfo_width() / 1920
-        timer_label.configure(font=("Chicago", int(ratio * -200)))
+        global current_size
+        try:
+            next_size = {
+                "format": timer.get_format(
+                    *(99 if x else 0 for x in timer.calc_delta())
+                ),
+                "height": root.winfo_height(),
+                "width": root.winfo_width(),
+            }
+            if current_size != next_size:
+                next_font_height = int(
+                    min(
+                        root.winfo_height(),
+                        (
+                            root.winfo_width()
+                            / fixed_font_instance.measure(next_size["format"])
+                        )
+                        * 250,
+                    )
+                )
+                font_instance.config(size=next_font_height)
+                timer_label.configure(font=font_instance)
+                current_size = next_size
+        except ZeroDivisionError:
+            pass
 
     def update():
-        delta = end_date - datetime.datetime.now()
-        if delta.total_seconds() < 0:
+        timer.update()
+        if timer.delta.total_seconds() <= 0:
             timer_label.configure(text="Now")
             timer_label.config(fg="red")
         else:
-            timer_label.configure(text=format_delta(delta))
+            timer_label.configure(text=str(timer))
         root.after(1000 - datetime.datetime.now().microsecond // 1000, update)
 
     root.bind("<Configure>", resize)