Six months ago my son Zac started to play a video game I knew very little about – which, as a games journalist, I found slightly disconcerting. Created by the Canada-based developer Digital Extremes, Warframe is an online sci-fi shooter, originally launched in 2013. Though little discussed outside its fanbase, it is consistently one of the biggest titles on Steam, with 75 million registered users. Set in a distant future version of our solar system, riddled with warring alien factions, the player takes part on the side of the Tenno, an ancient warrior race that employs barely sentient cybernetic fighters – the warframes of the title – as their primary weapons. Each day, Zac spends hours whizzing between planets, carrying out missions or exploring, all the while fighting enemies including a brutish clone army known as the Grineer, and the diseased, monstrous Infested.