save project

snake.py

@@ -57,9 +57,10 @@ while True:
     if x==apple_x and y==apple_y:
         apple_x=30*random.randint(0,21) 
         apple_y=30*random.randint(0,15) 
-      
+    else:
+        position.pop(0)  
     position.append((x, y))
-    position.pop(0)
+    
     # 将背景图画上去
     screen.blit(background, (0, 0))
     # 将贪吃蛇的头画上去