I didn't think much of SquareCells when I first saw it, doing my daily browse through the ever-increasing waves of games coming out on Steam. But closer inspection revealed a cross between Minesweeper and Sudoku that was extremely hard to walk away from, and I ended up checking out every game in the series.
Given a Minesweeper-like board, players have to declare which squares are the "mines", and get rid of those which are safe. Numbers outside of the board will tell you how many mines are in that column or row, and the way they're presented will tell you if the mines are stuck together or now. Numbers that you find on actual squares indicate how many squares are within that chain, not counting diagonal movement. You'll get less and less info as you go along, just like those old grid-based logic problems.
The game never outright says there are "mines", though. They're just fun little squares to interact with. All throughout, it maintains a very calm, ambient atmosphere. Gentle music, the white background, and a minimalist feel to everything -- it'd put you to sleep if it weren't so bright and addictive.
I'm always careful when I use that word, because "addictive" is not the same as "fun". But this game is both, and the logic needed to complete levels is greater than the games it's inspired by -- be that Minesweeper, Sudoku, or even its predecessor, Hexcells. The combination of column and row hints, with the hints on the actual board, force you to switch back and forth between different kinds of logic.
Part of its appeal is its price -- for around $3, SquareCells is quite cheap, though once you've completed its levels, you have to wait until designer Matthew Brown releases more. And if you've played any of it, you're likely addicted, meaning you'll happily grab any new content that comes out.
After going back and playing Hexcells (I really wanted more of the same style of gameplay), I had similar fun, but it did get a little formulaic after a while. There were certain rules I could follow in Hexcells that made the job a little too easy. Similar rules exist in SquareCells, but it forces you to apply those rules three or four moves ahead, just to see if chipping away at one of those squares is logically possible. It makes you keep a lot of information in your head at once, and ends up being both harder and more enjoyable.