Have You Played… Hoplite?
Hoplite has been an instant install on any new phone I buy since before I'd left university. It's an unassuming turn-based roguelite where you play as a Hoplite deftly moving from enemy to enemy, from tiny map to tiny map, in search of a Golden Fleece. It's also the first thing that comes to mind when I try to dredge up a list of games that pare back their chosen genre until what remains is the absolute essentials and nothing else.
Hoplite's genius is that its rules are so incredibly easy to understand. Your Hoplite can kill any enemy by moving from one enemy-adjacent tile to the other (a stab), or by directly approaching the enemy and closing the distance between you (a lunge). You also have three abilities, each of which you can use instead of moving: a shield bash which knocks an enemy away one tile; a leap, which uses up energy in order to close larger gaps in a single move; and a spear throw, which gives you a ranged attack but forces you to retrieve your spear afterwards before you can lunge attack again. Each of these abilities can be upgraded alongside other aspects of your character's ruleset with each cleared room, adding enough variation between runs to keep me playing on-and-off for seven years.
The enemies are even easier to understand. If you're in the direct line of fire of an archer at the end of your move, you'll lose one hit point. If you are adjacent to a bomb or a footman when your move ends, you'll lose one hit point. Within 60 seconds of picking up the game, you understand everything about how it works. Which means when you inevitably die, you only have yourself to blame, and your inability to look ahead enough turns to see the danger that was always visible and approaching.
The levels always start pitifully easy (unless you try Challenge Mode), but they quickly ramp up in difficulty as more enemies are added. It starts to feel quite like Into The Breach in that you can almost always see where every enemy will go next, because their rulesets make them so predictable. And yet, sooner or later there always arrives a tipping point where the number of enemies generates enough complexity that you can no longer trust your own precognition. It's because of this careful balance between intuitive rules and escalating challenge that Hoplite has earned its place as one of perhaps three or four absolute gems on the Play Store.