The aim of the game is to trip or dump the opponent onto the ground – his back, torso or butt must touch the ground. Each match lasts four minutes and is overseen by a referee. Punching, kicking, and gripping clothes are not permitted. Tactics include: distracting your opponent by tapping his head, tripping your opponent by grabbing his ankle or by sliding your leg underneath his leg, or lifting your opponent’s body entirely and dumping him on the ground. For thousands of years, ritualized hand-to-hand combat has been a fixture of life for the dozens of distinct tribes that constitute the Nuba. The individual customs vary among communities—some hold elaborate tournaments to mark the planting or harvest seasons; others wrestle as part of wedding celebrations—but the common practice is part of the cultural glue that holds the Nuba together. Nuba wrestling originates from the Nuba peoples, who are a diverse group of ethnolinguistic identities, based in the Nuba Mountains region of Sudan in the South Kordofan state located in southern Sudan(near the border with South Sudan). Since the British colonial era, many Nuba migrated to Khartoum. Nowadays, ethnic groups other than the Nuba also participate in wrestling. Outside the remote mountain villages where it developed, this ancient tradition itself has evolved. The 1960s was when the government in Khartoum began to disrupt the Nuba traditional way of life by implementing large, mechanized agricultural schemes, almost always administered by outsiders. A brutal campaign of forced Arabization and Islamization followed, and Nuba traditions like wrestling and brewing beer were either banned or altered to fit the government's tastes. Wrestlers no longer fight naked, covered in ash, or soaked in grip-resistant cow butter. The uniform of today's wrestling champion is athletic shorts and a sleeveless white T-shirt.