In hindsight, and with all apologies, Spelunky is like smoking. I got into it in part because it's what all the cool kids were doing at the time. It was embarrassingly easy to get wrong at first, but quickly became a soothing, easily-consumed daily habit. This lead to an effortless-seeming fluency, internalising both the basic routines and the nuanced flourishes that come from years of increasingly instinctive repetition. And it kills me. Death is certain, usually accidental but never escaped - if you reach either of the game's endings, something it took me about three years and perhaps five hundred hours' play to be able to do more than one in every twenty tries, the final score screen lists cause of death as "old age".
The magic comes from the ingredients being so simple. At heart, it's a roguelike disguised as a basic and sweetly-styled platformer: you run, you jump, you have a simple melee attack and you have some bombs you can throw. Everything you encounter has a very simple moveset, and kills you. Spikes kill you instantly if you fall on them. Blocks kill you instantly if they fall on you. Bats drift towards you on a shallow diagonal trajectory, and can easily nibble away your health points if you don't hit them just so. Frogs hop, and do the same. Small aliens zap you from their saucers - although you can bring the saucers down by throwing something, which causes them to explode and kill you. This can happen on the other side of the level, without your involvement, and you only know it from the sound of a distant explosion from which a landmine comes flying out, and hits you, and kills you.
On each death, the world is remade: each cutely-themed level randomly regenerated, the enemies randomly placed, the route to the exit strewn with challenges that are individually very simple but combine in endlessly treacherous ways: the bat which knocks you into a tiki trap, the monkey that knocks you into a spike pit, the yeti which smacks you into the void. The appeal of Spelunky is the same live, die, repeat routine so cherished in the Souls games, but with a platformer's simplicity that makes it far easier to understand and far more appealing to retry.