McKinsey Ecosystem Building Game: How It Works & How to Practice
The McKinsey Ecosystem Building game asks you to assemble a viable food chain from species that satisfy location, calorie, and relationship rules. Here is what candidates report, what it really measures, and how to train the planning and logic behind it for free.
TL;DR: The McKinsey Ecosystem Building game is the most famous task in the McKinsey Solve assessment (formerly Imbellus). You pick a set of species that survive together in one location, satisfying calorie needs and predator-prey relationships. It measures systems thinking and logic under constraints — and Solve records how you work, not just your final answer. You cannot rehearse the exact game, but the underlying planning and rule-following are very trainable.
What the Ecosystem Building game is
In the task candidates most often describe, you are shown a location — a mountain, a coral reef, or another habitat — and a large menu of plants and animals, each with data attached. Your job is to build a food chain that stays alive: choose species that belong in the chosen terrain, feed each other in a workable predator-prey structure, and collectively balance out on calories so nothing starves.
People search for this game under a pile of nicknames — the "coral reef" scenario, the "mountain" version, and even the "sea wolf" game — because the habitat and the artwork change between sittings. It is all the same underlying puzzle. McKinsey Solve itself is the successor to what applicants used to call the Imbellus test or the Problem Solving Game, so older write-ups you find may use those names.
One honest caution: McKinsey does not publish the rules, and the game set is refreshed over time. Treat your official invitation and its built-in tutorial as the source of truth, not any single account online.
What it actually measures
Strip away the wildlife and this is a constraint-satisfaction puzzle. You are holding several rules in your head at once — location fit, calorie thresholds, who eats whom — and searching for a combination where all of them are true together. That is systems thinking (seeing how one choice ripples into others) plus disciplined logic under constraints.
The part candidates underrate is that Solve captures process data. It logs how you explore the options, whether you check the rules before committing, how you revise after a mistake, and how methodical your search is. Two people can reach a similar answer and score differently because one worked systematically and one guessed. That is also why chasing "the answer" misses the point — the assessment is partly grading your approach.
How to practise the skills (free)
You cannot download the real Ecosystem game, and you should not want to. What you can train are the two habits it leans on: methodical planning and rule-based logic.
Start with the pathfinder puzzle. It forces you to plan a route that satisfies constraints before you act, and to re-plan calmly when your first idea hits a wall — the exact loop the ecosystem task rewards. Then use inductive reasoning to sharpen how you infer and apply rules from what you are shown, so that checking "does this species actually fit every condition?" becomes automatic rather than something you skip under time pressure.
Both train the underlying skill, not a replica of the McKinsey game. The transfer is in the working style: read the constraints, plan a candidate solution, verify it against every rule, adjust deliberately.
The rest of McKinsey Solve
The Ecosystem game is one module in a larger battery. The McKinsey Solve game guide walks through the full assessment and how it is scored, and the complete guide to game-based hiring assessments places McKinsey alongside HireVue, pymetrics, and Arctic Shores so you can see the wider landscape.
If your invite also mentions a defense scenario, the McKinsey Plant Defense game guide covers that planning-under-pressure task.
FAQ
Is the "sea wolf" game the same as the Ecosystem Building game? In most reports, yes — "sea wolf," "coral reef," and "mountain" are just different habitats or nicknames for the same build-a-food-chain task. The core rules candidates describe are the same.
Can I get the answers to the Ecosystem game? No, and they would not help. The species menus and correct combinations change between sittings, and Solve grades your process as well as your result — so a memorised answer, even a real one, cannot fake the methodical working the tool is watching for.
How much does speed matter? Working steadily and checking the rules beats rushing. A clean, systematic solution reads better than a fast, sloppy one that violates a constraint.
Do I need biology knowledge? No. Everything you need — calories, habitat, who eats whom — is given in the task. It is a logic puzzle dressed as an ecosystem.
GamePrep is an independent practice platform and is not affiliated with McKinsey & Company. McKinsey does not publish its game rules and the Solve assessment changes — verify everything against your invitation. We provide related skills practice only — no leaked questions or answers.