diff --git a/source/constants.py b/source/constants.py
index 9030499..7f83ea1 100755
--- a/source/constants.py
+++ b/source/constants.py
@@ -13,6 +13,8 @@ GRID_Y_LEN = 5
 GRID_X_SIZE = 80
 GRID_Y_SIZE = 100
 
+# 游戏速度倍率（调试用）
+GAME_RATE = 1
 
 WHITE        = (255, 255, 255)
 NAVYBLUE     = ( 60,  60, 100)
diff --git a/source/state/level.py b/source/state/level.py
index be713c7..f013e6c 100644
--- a/source/state/level.py
+++ b/source/state/level.py
@@ -628,13 +628,13 @@ class Level(tool.State):
                         hypno_zombie.setAttack(zombie, False)
 
     def checkCarCollisions(self):
-        collided_func = pg.sprite.collide_circle_ratio(0.6)
         for car in self.cars:
-            zombies = pg.sprite.spritecollide(car, self.zombie_groups[car.map_y], False, collided_func)
-            for zombie in zombies:
-                if zombie and zombie.state != c.DIE and (not zombie.lostHead):
+            for zombie in self.zombie_groups[car.map_y]:
+                if zombie and zombie.state != c.DIE and (not zombie.lostHead) and zombie.rect.x <= 0:
                     car.setWalk()
-                    zombie.setDie()
+                if zombie.rect.x <= car.rect.x:
+                    zombie.health = 0
+                    zombie.kill()
             if car.dead:
                 self.cars.remove(car)
 
diff --git a/source/tool.py b/source/tool.py
index 2de067c..19675b9 100755
--- a/source/tool.py
+++ b/source/tool.py
@@ -54,7 +54,7 @@ class Control():
 
     def update(self):
         # 返回自 pygame_init() 调用以来的毫秒数
-        self.current_time = pg.time.get_ticks()
+        self.current_time = pg.time.get_ticks() * c.GAME_RATE
 
         if self.state.done:
             self.flip_state()