For teachers
Metroji gives you one city a day, described in five emoji, with six guesses to name it. Every wrong guess reports the distance and the compass direction to the target, so a class narrows down the map together rather than shouting out capitals at random. It takes about five minutes, needs no accounts, and there is nothing to prepare.
The same city goes out to everyone in the world on the same day, so it is a genuine shared problem rather than a worksheet. Students who know nothing about the target can still contribute, because a wrong guess in roughly the right hemisphere is useful information for the next one.
The distance and bearing feedback is the part that does the teaching. A class that guesses Cairo and learns the answer is 4,200 kilometres northwest has to reason about scale and direction to get anywhere, and that reasoning is the lesson.
The clues are built from landmarks, food, industry, climate and history, so the reasoning ranges across the subject rather than testing recall of capital cities.
Easy mode gives a single guess and four cities to choose between, which turns the task into elimination and works well with younger or less confident groups. Hard mode drops you to five guesses and hides the distance, leaving only the direction, which is a genuine challenge for a strong class.
Past cities are playable from the archive and do not affect anyone's streak, so you can pick a city that suits the unit you are teaching rather than taking whatever the day offers.
Every city that has been an answer has a page explaining what each of its five emoji refers to, along with its coordinates and its distance from the nearest other cities in the game. They are written to be read by a student.
The obvious use is as a follow-up: reveal the city, then ask groups to work out why each symbol was chosen before checking. The pages also work as a research starting point for a place study.
There are no accounts and no sign-in. Nobody types a name, an email address or anything else identifying, because there is nowhere to type one.
Game data never leaves the browser. Streaks, statistics and play history are stored in the browser's own local storage on the device, are not transmitted anywhere, and disappear if the browser data is cleared. There is no server holding student records because there is no server.
The site does use Google Analytics to count visitors and to see which features get used. That sets cookies and collects the usual aggregate traffic data. It is not linked to any individual and it does not collect anything students type, but it is a third-party analytics tool and you should treat it as one when checking against your own policy.
There is no advertising, no chat, no user-generated content and no way for players to contact each other.
Nothing needs installing. It runs in any modern browser, including on a managed Chromebook, and works on an interactive whiteboard as well as on individual devices.