[10] Hexcells
It's hex grid Minesweeper, with extra features. Doesn't sound like much, but it has a surprising amount of depth to it. If you enjoy puzzles, you will absolutely love this. Just remember that there is ALWAYS a way to figure out the next step for CERTAIN.
The third game (Hexcells Infinite) has the most amount of content and also comes with a random level generator. The random levels aren't nearly as good as the crafted ones, but it's still a nice feature to have for when (or if) you ever manage to beat the campaign. If you're only going to buy one, go for that one.
https://store.steampowered.com/app/265890/Hexcells/https://store.steampowered.com/app/271900/Hexcells_Plus/https://store.steampowered.com/app/304410/Hexcells_Infinite/ 