更新 'ship'

ship

@@ -26,7 +26,7 @@ class Ship:
     def update(self):
         """根据移动标志调整飞船的位置"""
         # 更新飞船而不是rect对象的x值
-        if self.moving_right and  self.rect.right < self.screen_rect.right:
+        if self.moving_right and self.rect.right < self.screen_rect.right:
             self.x += self.settings.ship_speed
         if self.moving_left and self.rect.left > 0:
             self.x -= self.settings.ship_speed
@@ -36,4 +36,9 @@ class Ship:
 
     def blitme(self):
         """在指定位置绘制飞船"""
-        self.screen.blit(self.image, self.rect)
+        self.screen.blit(self.image, self.rect)
+
+    def center_ship(self):
+        """让飞船在屏幕底端局中"""
+        self.rect.midbottom = self.screen_rect.midbottom
+        self.x = float(self.rect.x)