Have you played either of the Candy Box games? They're text and ASCII-based adventures that start off very simple but open up into huge RPGs over time.
A Dark Room is very similar to those games. And it's surprisingly engrossing.
At the beginning, you awaken inside a dark room with blurred vision and a throbbing head. There's a single button to tap labelled "light fire".
Lighting the fire causes the room to warm up. But you'll have to continue stoking the flames, otherwise it will return to its earlier cold state.
Tap it up
The game just seems to involve your tapping that 'light fire' button at the start. There are small textual descriptions of the surroundings and events accompanying your taps, but that's it.
Trust me, there's much more to discover.
Soon, a female stranger will notice the fire in the room and barge in to find warmth. Once the stranger has warmed up sufficiently, she'll help you gather firewood and build traps to catch animals for meat.
I won't spoil the experience any more, for A Dark Room's strengths are in its surprises. After a while, the game expands terrifically as you're managing lots of resources and heading off on adventures.
Perhaps you consider it a bit of a risk to spend £1.49 / $1.99 on A Dark Room on the App Store. That's understandable. So, go try out the free browser version of the game.