What's new: unique killer puzzles, avatars and a promo video

Three things landed in Coffee Sudoku this month. One under-the-hood, one small bit of fun, and one I haven't tried before.

The killer puzzles are now provably unique. Every cage layout that ships in the app has been run through a solver that searches the whole space and confirms there is exactly one solution. The old check was bounded — mostly fine, but every few weeks I'd get a bug report saying I finished it but the app says it's wrong, or this can be done two ways. Both annoying. Fixed now.

The proof is the slow part, so I don't run it on your phone. Four hundred verified puzzles ship inside the app, a hundred per difficulty. While you're playing, a background worker quietly generates more so the pool stays full. You shouldn't notice any of this happening. That's the point.

Second thing: avatars. There's a small editor where you can pick hair, eyes, mouth, what your avatar is wearing, skin tone, and background colour. Tap your avatar in the profile menu and it opens. It's not deep — no unlockable cosmetics system, you just pick a face you like. The editor follows whichever theme you have on. I gave mine a coffee-coloured background. Obvious choice.

Third thing: there's a promo video now. About thirty seconds. It walks through opening the app, doing a puzzle, finishing it. You can watch it here: https://www.youtube.com/watch?v=bvxKtU1KviI. If you already have the app you don't really need a trailer for something that lives on your phone. But if you're sending it to a friend, or explaining why you keep talking about a sudoku app at brunch, the video does that better than I can in a text message.

That's it for April. Killer puzzles you can trust. Avatars if you want one. And a short video. Same pitch as always. Free. No ads. No account. No nonsense.