diff --git a/sim_scenes/solar_system/sun_earth_moon.py b/sim_scenes/solar_system/sun_earth_moon.py
index 3395ccd62e54668977227f0a4c640e7b362199c1..b26c69df9ec70ebb4310e81f26506828f95bdb7b 100644
--- a/sim_scenes/solar_system/sun_earth_moon.py
+++ b/sim_scenes/solar_system/sun_earth_moon.py
@@ -24,11 +24,11 @@ if __name__ == '__main__':
     # 观看月相变化的过程：分别是 新月、蛾眉月、上弦月、盈凸、满月、亏凸、下弦月、残月
     # 参考：images/moon/月相变化过程.jpeg
     # TODO: 月球在摄像机的前方（从 “新月” 开始）
-    # moon_pos, moon_vel = [0, 0, 384400], [-(EARTH_INIT_VELOCITY + 1.023), 0, 0]
+    moon_pos, moon_vel = [0, 0, 384400], [-(EARTH_INIT_VELOCITY + 1.023), 0, 0]
     # TODO: 月球在摄像机的右方（从 “下弦月” 开始），将会从右方出现
     # moon_pos, moon_vel = [384400, 0, 0], [-EARTH_INIT_VELOCITY, 0, 1.023]
     # TODO: 月球在摄像机的左方（从 “上弦月” 开始）
-    moon_pos, moon_vel = [-384400, 0, 0], [EARTH_INIT_VELOCITY, 0, -1.023]
+    # moon_pos, moon_vel = [-384400, 0, 0], [EARTH_INIT_VELOCITY, 0, -1.023]
 
     bodies = [
         sun,
diff --git a/simulators/ursina/entities/body_trail.py b/simulators/ursina/entities/body_trail.py
index 3f4cb06c1a42c26fd7034f35ca68c23dc2ce8608..7b43d9ed7ddaf04a0bf5cd3ba32d15599f130f08 100644
--- a/simulators/ursina/entities/body_trail.py
+++ b/simulators/ursina/entities/body_trail.py
@@ -51,3 +51,21 @@ class BodyTrail(Entity):
             a_text.parent = self
             a_arrow.enabled = False
             a_line.enabled = False
+
+
+# class BodyTrail(Entity):
+#     def __init__(self, **kwargs):
+#         from_pos = (0, 0, 0)
+#         to_pos = (1, 1, 1)
+#         super().__init__(
+#             # model='line',
+#             model=Mesh(vertices=(from_pos, to_pos), mode='line', thickness=3),
+#             ignore_paused=True,
+#             **kwargs
+#         )
+#
+#     def update(self):
+#         self.look_at(self.parent)
+#     # line = Entity(parent=parent,
+#     #                 model=Mesh(vertices=(from_pos * len_scale, to_pos * len_scale), mode='line', thickness=thickness),
+#     #                 color=color, alpha=alpha)