The logical conclusion of roguelikes.

I've tried 'em all, and usually you get to a point where you've made a build so unkillable you just play until you get bored or the game ramps up in a way where even an unkillable build is overrun.

Vampire Survivors is a very simple roguelike where you pick up and combine items to kill very simple enemies in a very simple map.
It has all the joy of roguelikes: Finding new weapons, combining them in interesting ways, working out which ones are good and bad, and slowly re-evaluating them over time.

Over the course of 30 minutes the game gets steadily more difficult, occasionally throwing waves that seem impossible to beat. But you will beat them, learn something new and get a little further.

Eventually the game is no challenge. You stand still and kill everything; you've solved the game.
As a reward, at the 30 minute mark the Grim Reaper shows up and kills you.
The only way to survive for 30 minutes is to have a broken build and your reward is death.

It's roguelikes as a genre boiled down to its bare essence and sold for about £2.