GridMath

Pretty relaxing mathematical puzzle. There is a full guide on Steam, if you just want the achievements. if you try to do it solo, it's probably gonna you about 10-20 hours depending on your knowledge.

I do recommend the game, but only if you’re clear on what you're getting into. It’s exactly as advertised—math. It’s a straightforward collection of math and logic combination puzzles. The screenshots, description, and price are all accurate, so there's no deception here. If logic and math puzzles are something you enjoy, and you’re looking for a way to pass the time between meetings or in short bursts, this game will definitely work for you. It’s a great fit for those looking for a casual but mentally engaging experience.

Nothing special, just some boring math.

I do recommend the game so long as you expect exactly what it says to be. Yes, it's math. It's a simple collection of math & logic combination puzzles. The screenshots, description, and price do not mislead in anyway. So if logic math puzzles piques your interest to pass time between meetings, then this will work for you.