Resonance
The tennis court was shrouded in a light mist in the early morning, dew still clinging to the grass, and the crisp scent of earth filled the air. Just as Luo Yan finished adjusting the last camera, Qi Sheng walked in from the entrance, carrying a black sports bag. His pace was slower than usual, and his white tennis cap was pulled low, obscuring most of his face.
"Is the equipment all set up?" he asked, his voice slightly hoarse from the early morning.
“Hmm,” Luo Yan nodded, pointing to the tripod on the sidelines, “Shooting from three angles simultaneously should cover all the details.” She deliberately didn’t mention the “reflection point tracking” parameters that she had stayed up until the early hours of the morning to adjust—in order to accommodate Qi Sheng’s possible movement habits, she had increased the sensitivity by 10%, as if she were conducting a careful experiment.
Qi Sheng put down his sports bag, the zipper making a soft "rip" sound as it was unzipped. What he took out wasn't a professional tennis racket, but a practice racket that looked a bit old, with a piece of paint chipped off the edge of the frame, revealing the silver-gray metal underneath, like a shallow scar.
"Use this?" Luo Yan was a little surprised. This wasn't the school team's shared racket; it looked more like an old object that had been forgotten in the equipment room.
"Hmm." He ran his fingertips along the chipped paint. "This racket has good balance, making it suitable for finding the right feel for the game. It's not picky about the user." His tone was flat, revealing no extra emotion.
She didn't ask any more questions, stepped back behind the camera, and raised her hand, saying, "Let's get started, starting with forehand shots."
Qi Sheng stood in the center of the court, facing the net sideways. His left-hand toss of the ball was fluid and natural, the ball tracing a smooth and full arc in the air. His footwork was incredibly fast, as if he were on an invisible beat. The moment his racket met the ball, he flicked his wrist slightly, and the white tennis ball grazed the net, landing inside the sideline of the opponent's court, stirring up a small patch of grass.
With a loud "bang," the sound of the ball hitting the court was exceptionally clear in the empty court.
Luo Yan stared at the monitor screen, her breathing unconsciously becoming lighter. His movements were more dynamic than the standard demonstration: the knee bend was precisely at 135 degrees, the torso rotation perfectly engaged her core strength, and the follow-through of her wrist seemed meticulously calculated, the racket trajectory forming a symmetrical arc. The highlight on the screen—the "reflective spot tracking" marker she had adjusted countless times—slid smoothly along the direction of her forearm like a star guided by a thread, without the slightest deviation.
"One more time." Luo Yan pressed the record button, her voice a little strained.
The second ball, the third ball… The morning light gradually pierced through the thin mist, falling on Qi Sheng's profile, revealing his taut jawline and tightly pursed lips. Fine beads of sweat trickled down his forehead, sliding down his cheek to his chin, dripping onto the grass and spreading into a small, dark stain. During the tenth set, he suddenly changed his serving motion, abandoning the standard toss serve for a more energy-efficient slice serve. The ball bounced off the net, rolling along the net, and then bounced up on the opponent's side with a strange sidespin.
“This kind of serve…” Luo Yan peeked out from behind the camera, “There are no parameters for it in the system database.”
Qi Sheng wiped his sweat with a towel, took off his white tennis cap and casually hung it around his neck, revealing his slightly messy hair on his forehead: "When I used to coach beginners, some of them would always miss the ball, so I came up with this lazy method." He paused, his gaze falling on the camera on the sidelines, "Do we need to reshoot? Follow the standard technique."
“No need.” Luo Yan shook her head, her fingers flying across the keyboard. “This is more valuable; it can improve the ‘special serve’ module.”
Data collection took the entire morning. When they returned to the lab, Luo Yan's computer had a new folder named "QS," taking up nearly 50GB of space. Qi Sheng sat in the chair next to her, watching her import the video into the analysis software, his fingers unconsciously tapping the table, the rhythm strikingly similar to the frequency of his ball-hitting.
"How long will it take to get the results?" he asked.
“At least two days.” Luo Yan brought up the motion decomposition interface. “We need to compare your motion parameters frame by frame with the differences in the standard library, and we also need to train the model to adapt to your exertion habits.” She paused, then added, “It’s like… customizing a unique version of you for the algorithm.”
Qi Sheng's ears turned red. He didn't reply, but took a sandwich out of his bag and handed it to her: "I didn't eat breakfast, have something to eat." The edges of the bread were slightly burnt, like the kind you usually buy at the school convenience store.
The two sat in front of the computer sharing a sandwich; the only sounds in the lab were the hum of the software and the occasional swallowing.
"Um..." she mumbled, her mouth full of bread, "Of the beginners you coached, are any still playing regularly?"
Qi Sheng paused in his drinking, a crumb of bread stuck to the corner of his mouth like a tiny star. "I don't know," he smiled, wiping the crumb away, "but there's this guy who used to practice slice serves, and now he's become a systems expert."
Luo Yan pretended to stare at the screen, but her fingertips lingered on the keyboard for a long time.
Three days later, the model training was finally completed. When Luo Yan clicked the "Test" button, her fingertips trembled slightly. Qi Sheng stood behind her, his breath falling on the crook of her neck, carrying a hint of mint, reminding her of the dew on the tennis court in the early morning.
On the screen, a video of Qi Sheng's backhand shot began to play. A green recognition box accurately framed his movement, and an "Excellent" rating popped up next to the key parameters. The overall score at the bottom showed "98 points"—the highest score since the system started operating.
"It's a success." Luo Yan breathed a sigh of relief, but her back accidentally bumped into Qi Sheng's chest. His hand instinctively reached out to support her shoulder, and the warmth of his palm seeped through her thin shirt like a warm fire.
The two froze simultaneously.
Qi Sheng quickly withdrew his hand and put it in his pocket, his knuckles turning white. Luo Yan turned around and saw that his ears under the brim of his hat were as red as ripe cherries. Her heart suddenly started beating heavily, as if a drum was pounding incessantly in her chest.
"that……"
"I……"
They both spoke at the same time, then stopped at the same time, the air filled with a subtle awkwardness and an even more subtle sweetness.
“The model is very accurate.” Qi Shengxian broke the silence, his gaze falling on the screen, but he didn’t look at the score. “It’s more accurate than I expected.”
“Your movements are perfect.” Luo Yan lowered her head, twisting the hem of her clothes with her fingers. “There’s almost no error.”
“It’s not a matter of error,” he suddenly said, his voice very serious. “It’s because you understand.”
What do I understand? I understand the subtle adjustments in his movements, the habits hidden beneath the standard parameters, the 0.5-second pause in his wrist when he serves a slice, and the look in his eyes after each shot—as if confirming something, or as if waiting for something.
Luo Yan didn't ask, but simply looked up to meet his gaze. The sunlight from the laboratory slanted in, casting tiny spots of light in his pupils, like fallen stars.
"This weekend..." Qi Sheng's Adam's apple bobbed. "There's a youth competition at the city stadium. Do you want to go watch?"
Luo Yan's eyes lit up: "Is it the charity match you mentioned?"
"Yes." He nodded. "That little girl from last time is going to play in the finals."
“Okay,” Luo Yan said with a smile, the curve of her eyes like they had been kissed by the sun. “I’ll take the system to do some real-world testing.”
Qi Sheng smiled too, a very light smile, yet like a pebble thrown into a lake, rippling through her heart.
As they left the lab, the setting sun cast long shadows of the two of them, almost overlapping on the corridor floor. Luo Yan watched as her shadow was gently covered by his, and suddenly felt that the distance that had separated them, the past sealed away by time, were all quietly connected at this moment by data and the ball, by code and heartbeats.
The gymnasium was bustling with activity on the weekend. A little girl named Lele, dressed in a pink tracksuit, ran around the court like a little deer. Although her movements were still a bit clumsy, she played with exceptional seriousness. Qi Sheng sat on the coach's bench, holding a notebook, occasionally glancing down to write something. His profile appeared particularly gentle under the spotlight.
Luo Yan sat in the audience, opened her laptop, and the system was recognizing Lele's movements in real time. The green recognition box moved flexibly with her running. When Lele hit a beautiful slice serve, the system popped up an "Excellent" rating, exactly the same as Qi Sheng's score that day.
Luo Yan's heart trembled slightly.
After the match, Lele ran over with the trophy in her arms, looked up at Qi Sheng and asked, "Teacher Qi, is my serve the same as the one you taught me?"
"Hmm," Qi Sheng patted her head, "She's much better than many of the people I've taught." As he said this, his gaze swept across the crowd and landed on Luo Yan, with a hint of teasing and tenderness in his eyes.
Luo Yan's face flushed. She pretended to be adjusting the computer, but her fingertips typed a line on the keyboard: "Next time you collect data, use your usual silver-gray racket."
In the reflection of the screen, she saw Qi Sheng take out his phone, and when he saw the message, the smile on his lips was like a flower blooming in the wind.
His reply came quickly, consisting of only two words: "Okay."
The cheers from the stadium continued, and the laughter of the boys crashed against the dome, scattering golden fragments across the ground.
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