No one would likely call That Dragon, Cancer fun. The game revolves around its creators, Ryan and Amy Green, and the couple’s third son, Joel, who was diagnosed with an atypical teratoid rhabdoid tumor at 1. The result is a painful re-imagining of Joel’s four-year struggle before dying in March 2014.

Much game time is spent simply listening to or reading actual testimony from the couple — Amy’s voice mails for her husband, Ryan’s heart-wrenching explanation to his other young sons of why Joel can’t speak. Play through often hurts — not in a maddening way, but in a way that a great documentary stings your insides. It’s a cathartic feeling.

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Gamers try to solve basic puzzles, though some levels don’t really have an endgame. The player simply struggles — often to the point of wondering whether or not the game is bugged or frozen — before abruptly moving on to the next stage. These levels are meant to mirror the struggle faced by the Greens, who clearly did everything in their power to help their son.

That Dragon, Cancer isn’t all doom and gloom. Some levels drift into Joel’s perspective. Players are left to imagine what a 2-year-old — sick but happy — thinks when he looks at the mobile above his crib or at the top of the slide. This surrealism melts into the adults’ portions as well, with the common theme of avoiding impossibly black cancer cells — often disguised as trees or floating mines — remaining constant. This design gives the title an artistic flow seen maybe once or twice in a generation in the video game medium.

For a game to affect such serious themes and stimulate so many seldom-used emotions is a great achievement.