must be one

must be one is a number puzzle built on a single rule — the one in its name.

A grid of numbers. Four operators. Combine neighboring tiles with arithmetic and collapse the whole board down to a single 1. That's the entire game: all becomes one.

It reads as obvious for about three moves. Then it doesn't.

- One rule, no filler — no twenty-minute tutorial, no menus to dig through. You understand it in seconds and spend the rest of your time actually thinking.
- Always solvable — every stage is generated so that a solution is guaranteed to exist before you ever see it. If you're stuck, that's on you, not the board.
- A climb that keeps widening — early stages stay in single digits; later ones open the range up and the arithmetic gets meaner.
- Free, and quick to pick up. One stage on the train; look up an hour later.

From office-canard — a one-person studio making small, system-first games. If this one gets its hooks in, there are more small games where it came from.