As the shelling came closer to 10-year-old Artyom's neighbourhood, he was forced to swap his local playground for a bunker -- just like children across rebel-held east Ukraine.
Whenever the boom of artillery bombardments echoes over the separatist stronghold of Donetsk, Artyom's grandmother Lyudmila Tarasova quickly grabs him and hurries down to an underground shelter by their apartment.
But with fighting having intensified in east Ukraine for the past ten days, that survival reflex means Artyom and his grandmother have been living in their subterranean retreat constantly.
"Sometimes I go out to get some fresh air, but I can't stay and play for too long," Artyom tells AFP, his large, dark eyes gazing out from under his woollen hat.
The children of Donetsk -- once a bustling industrial hub of a million people -- have a strangely pale complexion these days, with eyes that focus on a point somewhere in the distance.
The thud of mortar fire has replaced the ringing of school bells as the 10-month conflict has worn on, and with the days punctuated by the sound of silence and artillery, the local children struggle to combat fear and boredom.
Some one thousand children around the city are forced to regularly seek shelter underground, the United Nations children agency Unicef estimates.
'My friends have left'
In the cavernous Soviet-era bunker that houses Artyom and his granny, there are another two children among the 40 people seeking safety behind the concrete walls and thick metal door.
"Almost all of my friends have left," Artyom mumbles in a monotone voice.
Now, he plays hide-and-seek among the makeshift beds with twins Sofiya and Rada, who are five years his junior.
Sometimes he likes drawing, he says: cars, his favourite football team's logo, people, the planet Earth.
Hanging from the walls, however, are only pictures of tanks, artillery pieces and missile systems.
Another photo shows a rebel fighter standing in front of three kneeling Ukrainian soldiers. "Sorry for the bombing," "We won't do it anymore," and "We promise," captions depict the three government troops saying.
Little Sofiya likes to draw too. "Mainly ponies," she says. "And my bed."
Concentrating on her colouring book, she does not lift her eyes as she sings a song extolling the virtues of Russian President Vladimir Putin at the prompting of her grandmother.
"I want to be a painter when I grow up," she says.
'Homework like a holiday'
In the Petrovsky district in the west of the city, Anya, 11, and her sister Olesya, 3, rarely venture out of their basement.
Shells fall regularly in this area only around two kilometres (just over a mile) from the frontline.
"I don't go any further than just outside the door," says Anya, sporting a pink jacket. Three metres (yards) away, a crumpled electricity pylon shows how close danger has struck.
"During the night when it goes 'boom' right nearby, it wakes me up," the young girl says.
Now, though, the two sisters have gotten used to the fighting and don't cry, their grandmother says.
As time drags on in their shelter, Anya looks forward to Wednesdays most, when her teacher calls her on the phone and gives her a few lessons.
"I love all the subjects, but my favourite is maths," she says shyly.
Schooling for the children of Donetsk is sporadic at best.
Schools reopened in October when clashes died down. But since the fighting picked up again in recent weeks, they've been gradually closed again.
"Doing homework feels like a holiday," says Anya's grandmother.
As the shells fall, four-year-old Misha carries on playing a car racing game on his basic computer console.
"There is nothing to do here beside eat and sleep, sleep and eat," says his mother, Natalia Snizhkovskaya.