Huang Siyu was on the fourth floor of her elementary school finishing her afternoon lessons when the ground began shaking violently. She started fleeing the swaying building in terror.

As the fifth-grader ran downstairs with her classmates the school collapsed, killing her teacher, she said. A chunk of falling debris crushed her left leg, and her schoolmates had to drag her away from the crumbling building.

"I was so scared," said the willowy 12-year-old, who was trying to be cheerful Saturday, though her parents were still missing after Monday's earthquake.

Siyu had no idea she was battling for survival in China's worst quake in three decades. The monster magnitude 7.9 quake was so strong that it was felt across thousands of miles away in Beijing and other cities, where terrified people ran from their office towers in the first jarring reaction to a disaster that has unsettled a nation growing comfortable with prosperity.

The fear gradually faded in Beijing, but the nightmare was just starting for Siyu. The girl, who likes math but wants to be a fashion consultant when she grows up, is from one of the worst-hit towns.

From her hospital bed, she recalled on Saturday how a class of first-graders was buried in the collapsed school and waited for rescue in Yingxiu, a town in Wenchuan county, the quake's epicenter.

"One little boy in the first grade was really brave. His name was Zhou Yuyan," she said. "When he and his friends were trapped, before they were rescued, he sang a song to comfort them. He sang 'Two Tigers"' — a popular children's tune.

State-run media reported that only 100 out of 447 students and teachers survived at the school.

The quake and the landslides it triggered knocked out mountain roads and phone service to Yingxiu, cutting off the town. Heavy rains hampered helicopter flights. Siyu waited two days to be flown to the West China Hospital in Chengdu, the capital of Sichuan province, where most of the serious cases were taken.

The flight to Chengdu was Siyu's first ride in an aircraft, but it left her with no special impression. "I didn't feel like I was flying," she said. "I was in so much pain."

Siyu — whose name translates as "thoughtful rain" — underwent surgery Wednesday to complete the amputation of her leg.

Millions of other people living near the epicenter suffered much the same misery and danger in a large swathe of Sichuan — a rugged southwestern province that's sometimes called the "Texas of China," compared to the U.S. state, because of its southern location and enormous size.

Factories were flattened, apartment buildings became piles of rubble and dams threatened to burst and flood vast areas already devastated by the quake. Homeless people left cities and towns in droves, while tent camps popped up along roads and in parks.

Tens of thousands of troops with shovels and little else were mobilized for often futile rescues and searches for the dead. By Saturday, the rescue effort had burgeoned to almost 150,000 soldiers and police, using hundreds of heavy earth-moving machines to cut through the debris. The government says it expects a final death toll of at least 50,000.

"My mother was buried for five days before they recovered her body. Five days!" said Chen Xiaofeng, a 44-year-old high school teacher, as he left the crematorium in the hard-hit city of Dujiangyan, north of Chengdu.

The crematorium chimneys belched black smoke all day as bodies were delivered by flatbed trucks, vans and three-wheel motorcycle carts. A man with a large can of disinfectant strapped to his back sprayed down the bodies as they passed through the crematorium's massive stone gate decorated with carvings of the Buddha and dragons.

The disaster was yet another big, unexpected challenge for China in an already difficult year. The country's leaders would like to just focus on one of the nation's most prestigious projects — the staging of the Beijing Olympics less than three months away. But in recent months, the communist leadership has been distracted by unrest in Tibet, snow storms that paralyzed parts of southern China and protests that dogged the Olympic torch relay overseas.

Many Chinese believe the quake is another sign that this is an unlucky year for the country. Numerology is popular in China, and a viral text message circulating among mobile phones noted the quake happened on May 12 — or 5-12, which adds up to eight — 88 days before the Olympics begin on Aug. 8.

Soon after the quake hit, Premier Wen Jiabao jetted off to the quake zone. Wen, a grandfatherly, empathetic figure, made special stops at demolished schools, where many of the victims died. The government has said nearly 6,900 schoolrooms collapsed, fueling anger among many Chinese who suspect shoddy construction pushed up the death toll. For many families, the dead child was their only offspring — a tragic side-effect of China's "one-child" family planning policy.

Three days after her operation, Siyu sat propped up with pillows in her hospital bed in a room shared with two other child quake survivors. Two hospital volunteers sat at her side and kept her chatting and laughing with games and a simple art project using crayons to color a fish and a cat.

"I like dogs better than cats because a dog really cares about you," she said. "A dog can save your life."

She likes to have her hair braided and twisted into a bun pinned on the side of her head. When her catheter leaked and soaked her pajamas with urine, she looked horrified and began to cry. She used to ask constantly where her parents were, her caretakers said, but not so much anymore.

When the nurses brought her bowls of dumplings and rice, she uttered a meek, "Thank you." One volunteer entered the room sweating after coming in from the muggy afternoon heat, and Siyu asked other visitors to give the woman a fan.

Throughout the hospital, residents of Chengdu who wanted somehow to help — a kindergarten teacher, a hairstylist and a child psychologist among them — were handed hospital badges and deployed to keep Siyu and the other injured company.

The conversation stayed away from the earthquake, though Siyu occasionally blurted out memories without prompting. She recalled that doctors wouldn't let her eat anything 12 hours before her surgery, and after the procedure, the first thing they fed her was watermelon.

Although she lost her leg, Siyu said she feels fortunate. After lunch, she stared at the patient across from her bed and noted the boy's head was wrapped with a white thick bandage.

"Look, he hurt his head, so I feel lucky," she said. "When the roof caved in, I put my hands and arms over my head and protected it."