Mindustry - a tower defense game
Shattered Pixel Dungeon - roguelike dungeon crawler
Simon Tatham's Portable Puzzle Collection - A collection of logic puzzles

Unciv

It's a Civilization 5 remake (with multiplayer!) that is lightweight enough to run on pretty much anything.

Shattered Pixel Dungeon

Roguelite, fork of Pixel Dungeon with more content and balancing. Has 5 regions, each has four normal levels and a boss level. Has some metagame stuff when you finish the game once. Those two characteristics make it only a roguelite.

Anuto TD

Handdrawn Tower Defense.

Mindustry

Build big industries/factories. Similar to factorio, but havier focus on the tower defense part. Maps are a lot smaller, enemies come in waves with a countdown and therefore a lot easier than infinite factorio.

Unciv

Sid Meier's Civilization IV remake and therefore a 4X turn-based strategy game

Vector Pinball

Simple pinball game with multiple tables

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Mindustry and Unciv have quite some mods available, mod browsers are integrated.

Shattered Pixel Dungeon, Mindustry and Unciv also have desktop versions. For Shattered that makes it easier to play with mouse/keyboard/gamepad on android and layout should also work with bigger/external screens. Don’t know if that’s also true for the other two.

FlowIt! Is a decent puzzle game.

Minetest and Mineclone2

mindustry. the controls are a bit awkward for mobile, but its an incredibly fun game

Xeonjia

I quite enjoy TowerJumper

@avidseeker lichess