The drone flew forward for about two kilometers, and suddenly, the image on the controller screen stopped moving, and a warning message appeared!

"I lost contact with the drone, but I didn't fly too far, the drone has a control range of 10 kilometers. Wu Yaoxia said loudly.

Wu Yaohua made the mark and walked over and asked, "Then do you remember the approximate location?"

"Well, it's in that direction, about 1,700 meters or so!" Wu Yaoxia pointed in the direction with his right hand.

"Let's go, go over and have a look. ”

The five of them walked quickly in that direction together, Wu Yaohua held a knife and a small shovel in his hand in case something unexpected happened, and everyone was a little nervous.

After walking for about half an hour, I came to the target position.

"It should be here!" Wu Yaohua observed it carefully and said, "But I don't see a drone here." ”

This is a clearing in the middle of several large trees, and there are no bushes on the ground, no visual blind spots, and you can see the general situation at a glance.

Everyone looked carefully at the branches and leaves of the big tree next to them, but they didn't find any trace of the drone.

"There seems to be something on that tree!" Ding Lingling said, pointing to a big tree.

"It moved, could it be a little murderer?" Wu Yaoxia asked.

"What kind of little murderer, what is it?" Ding Lingling wondered.

"He's talking about the little squirrel~ This kid always speaks with the accent of a classmate from the south. Wu Yaohua explained.

"Don't you think it's funny?" Wu Yaoxia spread his hands and said helplessly: "Brother, you just don't have a sense of humor." ”

"Oh, little murderer, little squirrel, hahaha, kind of interesting. Ding Lingling smiled, "It's not a little fierce Xu, it's not a fierce tree~"

"What could that be?" Wu Yaoxia walked over to the tree, trying to see it clearly.

Suddenly, Wu Yaoxia suddenly seemed to hit something and fell to the ground.

"Didn't I remind you to pay attention to the invisible wall, why did you still crash into it? Wu Yaohua shook his head and said.

"You said it yourself is invisible, how can you pay attention to the invisible things~" Wu Yaoxia said indignantly.

"It's good to be careful in the future, don't blame him. "Ding Lingling came to the round.

"So the question is, what about my drone? It must have been here that I lost contact. Wu Yaoxia said.

Yang Xingchen thought for a while, pointed to the invisible wall that Wu Yaoxia bumped into just now and said, "There must also be an invisible 'door' here, your drone has nothing to do with Peaches, it can fly out of this secret realm." ”

"Ahem~ Your wording is a bit wrong...... What didn't have a relationship......" Wu Yaohua said in a voice.

"Don't worry about these details, this is the same place as the stone wall after entering the secret realm. There should also be a door on the opposite side that can be entered. If there were no door, the drone would have hit an invisible wall and fell to the ground, not disappeared. ”

"Well, you have a point. Wu Yaohua nodded and said, "Let's experiment." ”

He pulled a bottle of water out of his backpack and gently threw it towards the invisible wall.

With a snap, the bottle hit the invisible wall and fell to the ground.

......

"Hahaha! Slap your face!" Ding Lingling couldn't help laughing.

"Brother, throw it higher, the drone flies much higher than where you throw it!" Wu Yaoxia said.

"Hmm. Then try again!" Wu Yaohua picked up the bottle and threw it high. But the bottle flew more than ten meters high, but it still hit the invisible wall and bounced back.

"I'll come!" Yang Xingchen picked up the bottle and threw it hard, only to see that the bottle disappeared when it flew to a place more than thirty meters above the invisible wall.

"It's really gone!" Wu Yaoxia said happily.

"It means that the door is open at the top, but there is no door below, so strange design. Yang Xingchen said.

"Do you have a notepad and a pen? I'd like to try my hand at sketching a secret place. Yang Xingchen said to Wu Yaohua.

"Yes!" Wu Yaohua took out a notebook and pen from his backpack and handed them to Yang Xingchen.

Yang Xingchen began to draw on the notepad with a pen, and said as he painted: "The drone flew here from here just now. According to Ding Lingling's account, the invisible wall here is a large circle. We were there just now. The place to enter this secret place is a door below, and here is a door above. In the center of the entire secret realm is a large round lake with a diameter of about 300 meters. Well, by the way, Wu Yaohua, how far can you walk in an hour?"

"If you keep walking, you should be able to walk more than five kilometers. ”

"It took you more than three hours to walk along the invisible wall last time, right?"

"Yes, almost. ”

"Then this invisible wall must be at least fifteen to sixteen kilometers in a circle. ”

"Well, yes. ”

"It took you half an hour to walk from the entrance to the lake, but after walking for more than three hours in a row, you must be a little tired, and you will walk a little slower, less than two and a half kilometers in half an hour. Adding the diameter of the Round Lake of 300 meters, the diameter of this circular secret realm surrounded by invisible walls is about 5 kilometers, the circumference is 15.7 kilometers, and the distance from the entrance to the Round Lake is 2.35 kilometers. Well, that's pretty much it. ”

Yang Xingchen showed everyone the sketch he had drawn, and pointed to the content on the picture and said: "This is the entrance, there is a door below, this is where we are now, and there is a door above." According to this reasoning, there should be a lower door at each of the four points of the circle, and an upper door at each of the four corners of the upper left, upper right, lower right, and lower left. ”

"It seems that this is possible. Zhu Yan nodded and said.

"Then let's go to the nearest point to see if there is a door below, and it's only two kilometers away. Wu Yaohua pointed to the dot on the left side of the circle above the painting.

"Well, go there and try it. Yang Xingchen closed the notepad and put it in his pocket, and took the lead and walked in that direction.

After walking for about two kilometers, Yang Xingchen carefully put his right hand in front of him and slowly walked forward, and after walking for a distance, his palm finally touched the invisible wall.

"This is it. Yang Xingchen turned to Wu Yaohua and said.

Wu Yaohua took out the mineral water bottle and threw it gently, and the whole bottle disappeared the moment it touched the invisible wall.

"You guessed it right!" Ding Lingling said with a smile.

"Then what should we do next?" Wu Yaohua asked Yang Xingchen.

"By the way, didn't you say you've seen a lot of fruit? Where? After all this walking, it's time to rest and eat. Ding Lingling said.

"I don't remember this at the time, it seemed that it was not too far from the round lake. Wu Yaohua said.