The game has you designing a metro system on the fly, drawing lines to connect stations so that you can transport passengers to their destinations; passengers are represented by shapes and need to be transported to destination stations corresponding to their shapes.
But it's not as easy as it sounds. As the map slowly zooms out to expand the available playing area, stations pop up every now and then so you have to modify your lines to reach those stations or draw new ones. You'll need bridges and tunnels to take your trains across rivers, so that your metro isn't a bunch of inefficient disconnected branches. And stations can only hold so many passengers at once, so you've got to use your other tools such as carriages and new locomotives to keep up with passenger intake; if any one station stays at capacity for too long, you'll be forced to close down your metro. Which will happen sooner or later.
All but one of the playable cities are based on cities featuring real-world metros, allowing you to try your hand at reproducing (at least in spirit, anyway) the various iconic subways of the world. New cities are occasionally added based on player input; in November 2020, the game integrated the Mini Metro More mod and added Steam Workshop support and documentation for custom maps, allowing players to recreate any city they'd like.
Playable cities and the systems they are based on, in order of unlock:
- London — The London Underground (alternate: London 1960)
- Paris — Le Métropolitain (alternate: Paris 1937)
- New York City — New York City Subway (alternate: New York City 1972)
- Chicago — Chicago L
- Berlin — Berlin U And S Bahn
- Melbourne — Melbourne Metro
- Hong Kong — Hong Kong MTR
- Barcelona — Barcelona Metro
- Osaka — Osaka Subway
- Stockholm — Stockholm Metro
- St. Petersburg — St. Petersburg Metro
- Montréal — Montreal Metro
- San Francisco — Bay Area Rapid Transit
- São Paulo — São Paulo Metro
- Seoul — Seoul Metropolitan Subway
- Santiago — Santiago Metro
- Washington, D.C. — Washington Metro
- Singapore — Singapore MRT
- Cairo — Cairo Metro
- Istanbul — Istanbul Metro
- Shanghai — Shanghai Metro
- Guangzhou — Guangzhou Metro
- Chongquing — Chongquing Rail Transit
- Mumbai — Mumbai Metro
- Lagos — Lagos Rail Mass Transit
Mini Metro features examples of:
- Acceptable Breaks from Reality: Many of the non-realistic elements can be forgiven for catering to the Rule of Fun. In real life, passengers usually have specific destinations in mind rather than a collection of acceptable ones, trains can seat more than 6 per car, stations usually have capacity in the hundreds, and so on.
- Automatic New Game: When starting the game for the first time, the game briefly shows the title screen and then immediately takes you to the tutorial subway, which, aside from a few visual guides on how to play, plays out just like a standard game. In subsequent startups, the game will take you straight to the title menu instead.
- Color-Coded for Your Convenience: Just like in a real metro, train lines are distinguished by map color. This is probably one of the few times where you should refer to lines by color rather than official names that refer to operating regions or termini.note
- Creator Provincialism: Auckland does not have an actual metro system. The existence of an Auckland level can be explained by the development team hailing from New Zealand.
- Critical Existence Failure: The rest of your network can run fine, but if so much as one station is overcrowded for too long, the entire metro must shut down.
- Easy-Mode Mockery: Endless mode cannot be used to unlock new metros.
- Endless Game:
- On Normal and Extreme, play continues until a station goes too long at max capacity without passengers boarding a train, indicated by a circular timer around the station.
- Endless takes it a step further, not even having a lose condition. Since there's no game over, your performance is measured not in total number of passengers leaving the system but simply the rate at which they exit.
- Gimmick Level: Many of the cities in the base game feature slight modifications on the core rules:
- Berlin limits the amount of tunnels you get; you only earn one per upgrade instead of the usual two.
- Melbourne features trams rather than light rail; trams are slower than trains, but don't need to accelerate before reaching top speed.
- Hong Kong, Osaka and São Paulo and features faster passenger spawns, while Hong Kong gives you two trains per week.
- Osaka also gives you a choice between two trains or a single high-speed train per week.
- Shanghai starts with five stations instead of the usual three.
- Cairo and Mumbai feature trains that can only carry up to four passengers, but offers two carriages per upgrade.
- The Workshop update added support for user-made maps allowing all of the above modifications and more, such as mixing all three kinds of train (normal, high-speed, tram) and customizing their speed and capacity, having separate lines for different kinds of train, or starting a map with permanent lines that can't be altered. Mini Metro More included multiple maps showcasing these mechanics, like Toronto and Central Rio.
- Just Train Wrong: The game refers to the high-speed trains you can get in Osaka as Shinkansen. Shinkansen is the name of the network of high-speed railways in Japan, not the term used for an individual train.
- Minimalism: The game is very simple when it comes to graphical representations, so as to replicate the look and feel of a subway map.
- Play Every Day: The Daily Challenge gives you one shot at a preselected difficulty-metro combination, with your final passenger score being submitted to online leaderboards. A new challenge is offered every day, and one of the achievements requires playing the Daily Challenge every day for a week.
- Real-Time with Pause: You can stop the game to edit your assets at any time.
- Scoring Points: In Normal and Extreme, you're scored based on how many passengers complete their rides and how many days your metro manages to last. In Endless, since you can't actually get a game over, you're instead scored based on the frequency at which passengers complete their rides.
- Unstable Equilibrium: As a game goes on, more stations pop up and they start generating cargo faster and faster. You in turn receive additional locomotives and others resources, but not quickly enough to keep up — you'll inevitably reach a point where there's simply too much going on for your trains to deal with.
Overcrowding at this station has forced your metro to close.
497 passengers traveled on your metro over 30 days.