Building a city builder: the basics of economy design
In a city builder or tycoon game the graphics catch the eye, but the economy decides whether you play for an hour or for a month. If money comes too easily, there is no tension. If it comes too hard, the player quits. Below are the basics we learned while making Construction Empire, with real examples from the game.
Sources and sinks: where money comes from and where it goes
Every game economy can be described with two lists. Sources (often called faucets) bring money into the game: a finished contract, rent, a toll. Sinks take it out: wages, fuel, materials, upkeep, interest.
If sources grow faster than sinks, the player piles up money with nothing to spend it on, and every decision loses meaning. If sinks grow faster, the game turns into a struggle to survive. A good economy keeps the two lists in a moving balance: each new level brings both new ways to earn and new things worth paying for.
In Construction Empire the first source is the simple one: you accept a contract for a house, your machines drive to the site, and when the building is done you collect the money from the roof. The first sinks are simple too: materials for the build and upkeep for the machines.
Upkeep: the quiet cost that makes decisions real
If machines cost nothing after purchase, the best strategy would be “buy everything”. So in the game every machine has upkeep. An excavator standing in the garage still costs money. One of the tips inside the game is not to buy more machinery than your sites need.
Upkeep is the designer’s most useful tool, because it turns every purchase into a question: will this earn me more than it costs? Without it growth is free, and free growth is boring.
Cash flow versus profit
New designers often look only at whether an activity is profitable. Players, however, go bankrupt not from a lack of profit but from a lack of cash at the right moment. A contract that brings a good profit in twenty days but needs materials today can push you into the red.
That is why the game has clear rules for a negative balance. When your account is below zero you pay 1% interest per day. After 14 days in the red insolvency begins and you have 15 days to recover: with a bank loan, or by selling machines, shares or property. Otherwise bankruptcy follows. The rule is strict but predictable, and it teaches the player to keep a reserve.
The bank is the other side of the same question. A loan is useful when it buys something that earns: machinery, a rail line, property. If it covers old losses, it only postpones the problem and adds interest.
Feedback loops: why the rich get richer
Positive feedback amplifies success. More finished contracts bring more reputation, and with it bigger contracts. In the game reputation stars unlock more valuable contracts and a larger credit line. It feels good, but left unchecked the leading player runs away for good and the game is over before its end.
Negative feedback slows growth that is too fast and helps whoever is behind. A missed deadline costs stars, upkeep grows with the fleet, and rivals in tenders do not stand still. The art is in the balance: success should be felt, but each level should demand a new skill.
Tenders are a good example. Rival firms in the game usually bid between 78 and 98% of the budget. A bid around 80% often wins and is still profitable, while below 75% you risk working at a loss. So the player always chooses between a better chance and a bigger margin, and no single bid wins every time.
Pacing and progression
An economy is also a clock. The first ten minutes should give quick, visible rewards: the first house, the first money on the roof. Later the rewards get bigger but come less often, and the decisions get more complex.
That is why levels unlock new systems gradually: branches in other cities, then railways and motorways, ports and airports, global tenders. Each new system comes with a new kind of income. Rail lines and motorways bring money every day from fares and tolls, without waiting for contracts. Rented property gives steady income between big projects. The player moves from “working for every euro” to “running a network”, and that shift is the feeling of growth itself.
Price and reward curves almost always grow faster than linearly, but not without limit. If every level doubles the numbers, after twenty levels they become unreadable and money loses meaning.
Choices with a cost, and avoiding dead ends
An interesting decision has at least two good answers. Should I buy a new excavator, or stock up while materials are on sale? Should I take the big contract with a short deadline, or turn it down so as not to lose stars? The game has a tip for exactly this: better to refuse a contract than to take it without the machines.
A designer must also watch for dead ends: states the player cannot get out of and does not understand. If the free plots run out, there are no new contracts, so the game offers a new district to buy. If the money runs out, there is a loan, the sale of assets and a clear deadline. The aim is for failure to be possible but never hopeless.
Tell the player why money moves
The most common complaint in tycoon games is “where did my money go?”. The answer must be visible: a report of income and costs by item, a short message on a big payment, a hint when the account is in the red. Each network in the game, railways, motorways and ports, has its own report. A good economy is not only fair, it is also explained.
Playtesting and tuning
No spreadsheet replaces play. Numbers are tuned by playing again and again: how long the first million takes, when the player first goes into the red, which button nobody presses. It helps to keep the values in one place, not scattered across the code, so you can change the price of one machine and see the effect at once.
If you want to see these rules in action, the game is free at imperia.temidasoft.com. And if you are curious about the technical side, read how browser 3D games work.