Thanks for the great reply scaryugly!
I played a version of this on pen and paper in uk, which had the basic gameplay. A 5x5 grid, three (I think it was the letters A, B C) and 2 spaces, with some letters and empty spaces already filled in.
Adding the minesweeper like number hints and the definitely occupied wildcards were my own additions.
I'll try to find if the version I've played before has an official name.
I like keeping to the 5x5 grid as it makes it very easy to see on the Playdate screen. I'll look into adding other variations in future updates.
This is the puzzle game I've played before, they're called 'ABC puzzles':- http://www.thepuzzleclub.com/abc-logic-puzzle.php
I realised that making the hints on the side refer to the middle letter / shape was better, as you could get away with not having hints on both sides of the grid (saving on screen real estate). Beyond that its a very similar game.
Amazing! Thanks for taking the time to respond in detail :)
I can absolutely see the 5x5 and hints being perfectly fitted to the playdate screen, similar to how Sketch, Share, Solve can't be more than 15x20 without requiring some UI/scrolling.
I'm really glad I know the name of the puzzle now, scratching the sudoku/minesweeper itch at the same time is such a trip!