Yesterday my boy came out of his room in the cottage we’ve rented for our holiday in west Scotland. “Dad,” he said. “I finished Spelunky.”

14 years old, GCSEs ahead of him, standing at the very brink between child and adulthood. Voice breaking, sometimes sullen. He still breaks into open affection with a hug, or, more frequently, a joke, but now we feel we’ve earned it. We still tell him what to do, but maybe he needs it less than we think.

“I killed King Yama!” he said, eyes bright. “I shotgunned his hands away so he couldn’t throw skeletons at me, and then threw four bombs at his head.”

It’s not like he’s played Spelunky solidly for the past seven years. In fact, he hadn’t played it for ages. But over the past month or so, he’s sunk right into it, slightly obsessively, maybe, often into descending spirals of mood, in which irritation at mistakes and happenstance leads to new mistakes.

He started this phase of playing by rushing through the levels, first with a residual fear of the ghost that appears after a few minutes, and later, foolhardy with the belief that pure motor skills are the key to Spelunky.

“Slow down! Take more care,” I’d say, knowing he was already way better than I’ll ever be at Spelunky.

“Yeah,” he’d flatly reply and go no slower. He’s not rebellious, nor truly stubborn, but he will only get to things under his own direction, once he’s quietly decided for himself.

I took the controller from him to find out in Spelunky’s Journal how many times he’d died to shopkeepers. 340. He’d died to bats 10 times.

“Maybe it’s not such a good idea to kill the shopkeepers,” I suggested. “I know they say it’s the best strategy, but…”

“But maybe I wouldn’t get so far. I always do best when I get a shotgun and a jetpack. It’s the best way to get them,” he said. And so he continued killing shopkeepers.

Over life after life, on our PS4 and on his Vita since we’ve been away, he’s wound his way through arrow traps and tiki men, the City of Gold and Hell. He’s followed guides to know the equipment he needs and the secret signs to look for. And he made it to Yama, without a sliver of my aid.

We read what I’d written about him and Spelunky when he was seven. He grinned wide. “I still like games where you can do what you want,” he said.

My boy loves Totally Accurate Battle Simulator and building vast armies of marines in StarCraft II against the AI on easy, and creating vast battleships in Cosmoteer. He’s gotten back into Minecraft. He’s still a little afraid of challenge, but when he’s gripped one, on his own terms, he will softly chip away through defeat after defeat and win.

I worry. I guess a parent does, not least when the end of childhood is in sight. But half a lifetime after he was first interested in Spelunky, he beat it.

“There’s loads I went straight past, like Vlad. I want to see what else is in Hell,” he said. “I’m definitely going to run it again.”

I first wrote about my son playing Spelunky in July 2012. Time goes too fast. I’ve also written about Spelunky’s design as part of my Mechanic series.