"He always uses new, complicated techniques to win," says Abdulla, a friend and competitor.
But checkers isn't the only thing draws Sharif to the park, which has long been one of the epicenters of political action in Rania, a town near the Qandil Mountains in the northern Iraqi region known as Kurdistan.
Sharif, who took up arms against Saddam Hussein's regime in the 1980s and '90s, is an elder statesman of the movement for Kurdish rights and independence, a long struggle that has been punctuated by violent disputes with both the Turkish and Iraqi governments.
The Kurdish homeland spans an area that overlaps Iraq, Syria, Turkey and Iran and edges into Georgia. The Iraqi government targeted Kurds with chemical weapons in the 1980s and the Turkish government has at times denied the existence of Kurds. It's illegal to speak the Kurdish language in official settings in Turkey.
The Rania Public Park, the center of a city known for militant activism, has long been a gathering place for residents to support guerilla and other fighters. But now, it's also the scene of frequent peace protests.
Sharif's son, Sarkawt Sharif, 24, was among a group of young people who staged a two-day hunger strike to draw attention to the plight of Kurdish prisoners in Turkish prisons.
"Nowadays, we cannot fight against a huge country, a member of NATO, like Turkey with AK-47s," Sarkawt Sharif said.
Kareem Sharif disagrees.
"To be free," Sharif said, "one needs to seize freedom and not only demand it."
Born into a family of Kurdish nationalists, Kareem Sharif joined the Peshmerga militia while still in his 20s. The Peshmerga (sometimes referred to as the Peshmargayaty) is the primary Kurdish military force and has borne the brunt of armed conflict in the name of Kurdish nationalism. In years past, many Kurds say there was unquestioned loyalty to the methods used by the Peshmerga, which include guerilla tactics. But now, Sharif is seen as one of an old guard who believes the best way for Kurds to regain their rights is through force.
Rania, known as "The Gate of Uprising," has long been a center of Kurdish nationalist activity. The city's neighboring mountains and the villages tucked within them are safe havens for Peshmerga forces.
In recent years, though, activists are more likely to use hunger strikes to bring attention to the Kurdish plight. Instead of dedicating all of their efforts to support the Peshmerga militia, money is often raised to support beleaguered Kurds in other areas, such as Syria.
Since the fall of Saddam Hussein, Iraq's one-time dictator who was executed in 2006 on order of an Iraq tribunal, the shifting nature of political activism in Rania has left Sharif and his generation of Che Guevara-inspired freedom fighters bemused.
Sarkawt Sharif and others who joined him in the hunger strike say they're influenced by Gandhi. They've largely traded the violent approach of the past for more peaceful methods.
The hunger strike was pre-empted by a much longer hunger strike in Turkey. For much of the fall of 2012, hundreds of political prisoners in nearly 80 Turkish jails staged a hunger strike that didn't come to an end until late November, when the jailed Kurdistan Workers Party, known by its Kurdish language initials PKK, leader Abdullah Ocalan issued an order for the strikers to desist. Some prisoners went without food for 68 days.
Ocalan is serving a life sentence on Imrali Island, a maximum-security prison in the Sea of Marmara. He was the only prisoner for several years.
The United States and other countries have designated the PKK a terrorist organization.
The strike in Rania drew the attention of crowds but also the consternation of Kareem Sharif, who said that the protest was needlessly provocative. It caused too much pain for the families involved, he said.
"Hunger strikes are useless because dictators care about as much for your death as they care about your miserable life," he said. "I hugely suffer when I see my son starving."
The hunger strikers say suffering was the point.
"Whoever knows the value of freedom knows that (the hunger strike) is worth it," said Rekar Hussein, a student at the American University of Iraq in Sulaimani.
Kareem Sharif struggles to understand his son's perspective. The older man's hard-line approach was forged three decades ago, in the mountains along the Iraqi border with Iran. Many Kurdish men had joined militias following attacks on Kurdish villages in which the Saddam regime used chemical weapons to kill tens of thousands of civilians. Human Rights Watch claims that Saddam killed 50,000-100,000 Kurds from 1986-'89.
Sarkawt Sharif doesn't deny the atrocities but begs a different response. Their debates sometimes become heated arguments.
"You are too conservative," he told his father scornfully, as father and son sat face to face in their home.
Sarkawt Sharif pointed his finger at his father, adding that his father doesn't read well, and has only read a few books. The older man doesn't understand new methods of ensuring that human rights are respected, Sarkawt Sharif said.
"We cannot always fight and kill!" he said "You're not aware that technology has greatly improved, so we cannot fight against the American/Turkish drones with AK-47s. If you go back to the mountains as you did before, you will be dead in less than two days. You will be dead while you are asleep or while you are on the back of your horse with your nonsense Kalashnikov seeking food as the drones find you anytime you move!"
Kareem Sharif disputes his son's claim that weapons used today are more dangerous than those used 20 years ago.
"When I fought, there were chemical weapons used against us, not ridiculous drones," he said angrily. "We never gave up. There were planes and helicopters that bombarded us!"
Kurds were being killed in Turkey every day on virtue of their ethnicity, Kareem Sharif said. Those in Iran were hanged in city centers. Sarkawt Sharif, Kareem Sharif said, is naïve and easily deceived by the promise of democracy and peace, notions he calls "modern."
"If you fight and win, as winning comes from fighting, there will be human rights to support you," he said. "Son, if you lose, what do these mean to you? But if you win, there will be everything you want. You can impose your will."
During his revolutionary days, Kareen Sharif suffered wounds from shrapnel. After two years of fighting, his wife joined him in the mountains. Sarkawt Sharif was born there. When Kareem Sharif speaks of those years now, his round face lights up. He says that he would happily take up arms in the mountains again, that Turkish atrocities against Kurds -- such as a drone attack along the Iraqi border that left a family of seven, including four children, dead in 2011 -- more than justify the use of force.
But Kareem Sharif's wife, Khadija said she is haunted by the memory of her husband's militancy, by the years they spend homeless and on the run and by visions of dead bodies.
"I suffered with my husband in the mountains," she said as she poured tea into three ceramic cups. "I never want to re-experience that miserable life. I never want my son to go to the mountains and fight."
Sarkawt Sharif says his mother has little to worry about.
"To make the world hear my voice," he said, "I'm ready to die in hunger but never want to be brutal or harm anyone."