Meet Coffee Sudoku

A few people have asked what is actually in Coffee Sudoku, so this post is the whole app in one read. If you have never opened it, start here.

At the centre of it is classic Sudoku. Four difficulties, from easy through very hard. Pencil marks. A timer you can hide if you do not want to race yourself. A mistake counter you can also hide. Pick how hard you want it, tap a puzzle, fill it in. That is the main loop and it is the same loop on every device.

Then there are three hidden modes that you unlock by playing. Finish Very Hard once and Zen mode opens. Errors stop being flagged, the mistake counter goes away, and you just solve at your own speed. Finish Zen once and Redacted unlocks. Numbers start vanishing from the grid every fifteen seconds, then every twenty seconds after that. You have to remember what was there. It is a memory test stapled onto a Sudoku grid. Finish Redacted once and Killer opens up. Cages with target sums, no given digits to start, a different kind of puzzle entirely. I wrote about Killer in more detail in another post.

The pitch is the same as it has been from day one. NO ADS. NO ACCOUNT. NO TRACKING. NO IN-APP PURCHASES. Ten languages, including English, Spanish, French, German, Italian, Portuguese, Romanian, Slovak, Japanese and Polish. Screen reader support, so it works for people who cannot use the visual interface. Everything you progress through is stored on your device, not on a server somewhere.

You can play it three ways. On iPhone, on Android, or in your browser at coffeesudoku.com. The website has the same generator and the same difficulty curve as the app. There is a share button at the top of any puzzle that gives you a link to the exact same grid, so you can pass it around. Useful if you want to send a friend the one that wrecked you. You can also pick an avatar from the profile menu, with hair, eyes, mouth, skin tone and background colour. Small thing, but I like having a face that is not the default.

The site also has a small academy if you want to actually get better. How to play, how to solve, beginner tips, advanced techniques, master techniques, and a technique atlas with worked examples. None of it is gated. Read what you need, leave when you are done.

That is the app. Grab a coffee, open it, play one. If you decide it is worth keeping on your phone, great. If not, no email list will chase you about it.