U Sein Lin, a retired history teacher in Myanmar, had never played a video game in his life. But about a month ago, while scrolling through Facebook, he stumbled on War of Heroes — The PDF Game.

He has been playing it nearly nonstop ever since.

For Mr. Sein Lin, 72, killing virtual Myanmar troops is a way of participating in real-life resistance to the country’s ruthless military, which has killed thousands of citizens after seizing power in a coup last year.

Since its debut in March, War of Heroes has been downloaded more than 390,000 times. Many players say they are motivated by the creators’ pledge to donate proceeds to help finance resistance forces in Myanmar, and aid those who have been displaced by the fighting.

“Even though I can’t kill soldiers who are brutally killing civilians, killing in the game is satisfying, too,” Mr. Sein Lin said. “One way or another, playing the game and clicking until I die will help the revolution.”

Myanmar’s military, known as the Tatmadaw, previously ruled the country for half a century and has long been at war with its own citizens. Since ousting elected officials in the coup last year, the regime has attempted to crush dissent by arresting opposition leaders, gunning down unarmed protesters, bombing guerrilla encampments and burning thousands of homes.