diff --git a/game/osu.py b/game/osu.py
index 7aa5257..f268835 100644
--- a/game/osu.py
+++ b/game/osu.py
@@ -38,8 +38,8 @@ class Circle:
 canvas = None
 mouse_x = 0
 mouse_y = 0
-tick = 0
-STEP_TICK = 60
+tick = 0.0
+STEP_TICK = 60.0
 
 # Circle
 circle = None
@@ -58,7 +58,25 @@ def main(c: tk.Canvas):
 
 # Loop
 def loop(deltatime: float, difficulty: float):
-    global tick
+    global tick, circle
+    print(difficulty)
+
+    # Step
+    if tick >= STEP_TICK:
+        # Tick or end?
+        if circle.value == 0:
+            # Check
+            if circle.isInside(mouse_x, mouse_y):
+                circle.delete()
+                circle = create_circle(difficulty)
+                tick = 0.0
+                return
+            else:
+                # TODO, lose
+                pass
+        else:
+            circle.decrement()
+            tick = 0.0
 
     # Highlight
     if circle.isInside(mouse_x, mouse_y):
@@ -66,7 +84,8 @@ def loop(deltatime: float, difficulty: float):
     else:
         circle.highlight(False)
 
-    tick += 1
+
+    tick += difficulty
 
 # Circle
 def create_circle(difficulty = 1.0):