Solitaire, straight out of classic Windows (pre-advertising death throes):

https://play.google.com/store/apps/details?id=com.potatojam.classic.solitaire.klondike

Hoplite, classic turn based dungeon/puzzle:

https://play.google.com/store/apps/details?id=com.magmafortress.hoplite

Card Crawl/Card Thief/Miracle Merchant are good puzzle-like games

Slice and dice

Not sure if it fits your criteria but the only mobile game I play is pinball deluxe. If you like real pinball, then you'll love it, it tries to stay as true to real pinball as possible on some/most tables, it does have small transaction stuff you can buy but I still haven't bought any including all the additional tables etc after playing it 6 months + and if you did, then it's just an 8€ one time buy to get all the content and remove the ads, I'm gonna get that once I actually get bored of the "free" tables.

A Dance of Fire and Ice is an incredible rhythm game that you buy once and that's it. I think there's an expansion pack but it's a single purchase. Whether that's your idea of "casual" really depends on what you like. You can always play chill low difficulty levels when you need to zone out, and high difficulty levels when you want a challenge. It can get stupidly hard.

You can try a demo online at that link. It told me webgl wasn't supported on mobile, but it worked pretty well for me just now on firefox, even if it was a bit laggy. It should work fine on PC.

I pirated it on PC after my kids told me about it and ended up buying it three times on Steam and twice on mobile. It's just that good. I've built a custom digital drum to play it and I'm now making a custom MIDI controller, so we'll see if that does better when connected to the game.

The game works as well on mobile, if not better because the touchscreen is so responsive.

A couple that I like:

• 80 Days - it's not free but I think it's worth it. It's a sort of steampunk version of Around the World in 80 Days where you have to plan your routes, and buy and sell things in different cities to make money. The main gameplay is sort of choose-your-own-adventure events that happen during travel and in different cities.

• Card Thief - I just started playing this recently. It does technically have a microtransaction but it's more like, they let you play for free if you don't mind waiting for chests to unlock, or you can buy the game to bypass this. The main gameplay is sneaking through dungeons represented by a 3x3 grid of cards randomly drawn from the deck; collecting treasures and avoiding getting caught.

"0h h1" is a fun, easy logic puzzle game that I find myself going back to when I have a minute to kill.

There are a lot of great suggestions here already, so I will just share Mini Review with you as a discovery tool. I like to use them because they have a lot of filters to help you find a mobile game. For example, here's their list for free, single-player, offline games with no ads or in app purchases, sorted by highest user score. They also have an app for both Android and iOS with the same info and filtering as the site.

You should download Mini Review

It is a currated version of the Play Store with many filters including paid/free, IAP, genres, ...

The reviews are very thorough and always include a paragraph about the "presatoriness" of IAP if any

Polytropia

Old school RuneScape, it has free "demo" version which you can easily put a 100+ hours in. And if you really love there is a subscription model that's kinda expensive if you bill monthly, but no other micro transactions.

desert golf and its follow up golf on mars are big hits at my house

I have clocked a lot of hours in Slice & Dice both on mobile and on PC well worth the 8 bucks even though I've paid it three times now I think. Honorable mention to Suika(Watermelon game) about 3 bucks on the Play store.

Rodent Rush, it’s similar to Chips Challenge from back in the day but a bit different, and imho it’s a better game.

It’s only on iOS though as far as I can tell.

I really liked Lara Croft GO. It's better than Hitman GO or other GO games.

Shattered pixel dungeon has been a mainstay on my phone for what feels like a decade now

2048

Andor's Trail, it's barely recogniseable as a "phone" game, other than that it does indeed run on phones. I don't remember if it had ads or anything, been taking it from phone to phone for over 10 years now. I don't think it had ads or anything. It's open source, but has a pretty consistent feel despite having like 50+ contributors so far.

It's an adventure RPG. The low level experience might be best with a bit of grinding, but.... casual grinding... lol. I kind of just wander around collecting "meat" until I feel strong enough to leave the areas near town and set out on the rest of the adventure. But there has been alot more work around town since the last time I started a new character. So it might feel more natural now.

Vector pinball

Any of the PAID games from Kairosoft. Dungeon Village, Grand Prix Story, Game Dev Story. He has since re-released all his games as f2p microtransaction junk, but the full price versions are generally really good.

I have a 2048 clone from F-Droid and a Solitaire-like games collection from F-Droid that keep me busy on flights, etc. No stress, easy, entertaining.

I don't think there's any meta progression as far as I'm aware, but I find Shattered Pixel Dungeon (available on both android and ios) to be a low stress enough game. I suck at it, so I've never gotten much further than the first boss fight, but the game is about running through randomly generated dungeons, going down floor by floor as one of 4 different characters.

Some good games I recommend are Alto's Adventure / Odyssey, any bejeweled game, Cell to Singularity, Idle Slayer, Monument Valley, Reigns, Sky Force Reloaded, and Stick Fight Shadow Warrior. Hopefully that's enough!

Assuming that you have Netflix, open it, scroll to games and open the section. There are tons of great games without any microtransactions or ads. They're overwhelmingly commercial games licensed by Netflix.

Neopets still exists and is going strong! The community is wholesome and so amazing, You can play it on your phone's internet browser, it's wonderful nostalgic break from everything else, and they have a TON of free games built in... Solitaire, Pyramids, Bullshit, Battleship, Minesweeper, Brick Breaker, Mahjong, Blackjack, Poker, Keno, etc.

I still play every day and have a BUNCH of goodies for new players, if you do check it out!

Wuthering Waves is Hella good. Technically it's an open world gacha game, but I played through all the storyline (the developers will be forever updating the story a la Genshin Impact), and I never spent a dime on it.

Also, I have spent money on Cooking Diary. However, I went about 3 months of daily play before I did, and it was more about me being impatient/telling myself "You got 3 months of daily play, you can drop the devs $4.99". I've played that game just about daily since Memorial Day 2023, and I've dropped $5.00 quarterly. There are regularly moments of infinite lives that exceed an hour or two, that it genuinely isn't necessary. I spend the money more as a "thanks for not making this ducking game contingent on microtransactions, making it good, and maintaining/update it."

I used to play Unblock Me. Made it maybe 1000 levels in various difficulties before stopping.

It doesn't quite fit, but there are a lot of boardgame phone adaptions, and they rarely have microtransactions. Cat lady, carcassonne, ghanz schoan clever, doppelt so clever, hex roller, rail road ink and roll player are some of my favorites

Flow is a fun puzzle game with a hint of nostalgia

Grand prix story and game dev tycoon.

Both good games, low stress, clear progression