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McKinsey Solve Game

McKinsey Solve Game (2024)

The Ultimate Guide for the McKinsey Problem Solving Game (aka Imbellus Digital Assessment)

Francesco Rieppi   |   May 28, 2024   |   37 min read


So you have crafted the perfect CV, found a great referral and applied to your top consulting choice – McKinsey.

You have even structured the ideal case interview prep plan to be ready in advance.

And now, out of the blue, they told you that you have been invited to the first stage of the process and have to take the McKinsey Solve game.

What? A game?

Yes, McKinsey has gone digital, and now, instead of a standard test (the old and proven PST) they will let you play with fish and wolves to understand your problem-solving skills.

Consulting firms are really evolving 😅.

If you think this is science fiction, think again.

You will have to play a game to get into one of the top strategy consulting firms in the world.

(Sorry BCG and Bain friends, they are still ahead, at least in terms of revenues and alumni).

But you don’t have to worry.

In this article, I will explain everything you need to know about the game so that you can be perfectly prepared and overcome the major obstacles in the McKinsey PSG.

Let’s start!

PS. This article is a long 30-minute read. 

But if you stick till the end, I promise you will learn more than from any other article online and most paid guides on the topic.

Study tip: If you are short of time, you can bookmark the URL and come back to this later for a deep dive.

Do you want to play the McKinsey Game in advance

Have a look at the McKinsey Problem Solving Game video simulation I created, now with the optional full simulation to play the Ecosystem and Redrock games

This is the ONLY simulation on the market with a 60-day, 100% money-back guarantee offering you the opportunity to play the McKinsey PSG before the actual test!

You can click on the image below to learn more.

What is the McKinsey Solve Game?

The McKinsey Solve Game, also called Imbellus, PSG, McKinsey Digital Assessment, gamified assessment and a bunch of other strange names, is a digital game where candidates have to play up to 3 games (in its latest version) to show their problem-solving skills in up to 90 minutes.

You will read a ton of old info telling you about disasters, diseases, defending plants from foxes and several other possible games. 

Well, let me share the news: that’s all old, outdated information. 

The new McKinsey Digital Assessment consists of a maximum of three games. 

The reason why I know this is that I created the only video simulation on the market with 300+ 5-star reviews, and I refund everyone who doesn’t pass the game (more on that later). 

But back to the McKinsey test: up to three games, as we said. 

So that’s what you have to prepare for. Forget about the other mini-games that are not needed.

(At the moment. Don’t worry, if there are any changes I will update this article right away so you will know in advance. I have skin in the game to update my stuff; otherwise I have to refund candidates!). 

The other games that McKinsey used in the past (and are no longer used now) are:

  1. Plant Defense – where you have to defend a plant from the attacks of invaders.
  2. Disaster Management – where you have to identify a natural disaster and relocate some animals to a new section of the island in order to help them survive.
  3. Disease Management – where you have to identify the cause of a disease affecting animals and the rules of their infection.
  4. Migration Management – where you have to move some animals on different maps managing resources to ensure survival.

So here is our simple goal for you today: learn how to do your best in the three current games of the Imbellus and secure an invite to your McKinsey interview. 

All while skipping the useless stuff related to the other games that are no longer needed (and that some sites still advertise so that you can buy more stuff from them!).

And if you are thinking “But maybe I might still get a different mini-game!” – don’t worry. 

I receive daily, real-time feedback from the candidates who purchase my simulation so as of today (when you read this article, as I constantly update it), the games are still the same. 

And if you still want to prepare for the others, you can find them anyway in my 153-page PDF guidebook that is included for free in my course here.

In this article, I will cover for you:

  1. The real games tested in the McKinsey Problem Solving Game (plus an overview of all the others, so that you can save time with your prep).
  2. The components of each game and details of what is required for each of them.
  3. The key tips to be ready for the assessment.
  4. A complete example of a working chain for the Ecosystem Building Game.
  5. The most common questions asked related to the McKinsey Game.

Are you ready?

Then let’s start our journey!

What are the current games of the McKinsey Problem Solving Game?

As I told you before, currently McKinsey is exclusively using three games: the Ecosystem Management Game, the Redrock Study and the Ocean Treatment Game

If you read something else, that’s outdated information.

Specifically, you might have heard about the Plant Defense game, where you had to defend a plant species from invaders.

That game is gone. It was replaced at the end of February ’23 by the Redrock Study.

In this article, I will tell you what to focus on in order to have a great performance with all the current games. 

Let’s start with game #1: Ecosystem Game.

Ecosystem Management - How does it work?

The Ecosystem  game (also called Ecosystem Building game or Ecosystem Creation) has been the core of the McKinsey game from the start – 100% of the candidates I have helped so far had to play it as the first game. 

You have probably seen several images of the game itself and are relatively familiar with it exactly because it is the one candidates encountered the most.

Here is a screenshot of what the game involves (source: my guide):

McKinsey Problem-Solving Game Ecosystem

Here is the plot of the game: you have been set on an island and have to find the conditions for an ecosystem to be sustainable in a chosen location.

Your goal in this game is to:

  • Create a sustainable chain of 8 species and
  • Find a suitable location for your chain.

Both tasks should be completed with a time constraint of 35 minutes.

Now that there is the Redrock Study as the second game, there is an important difference related to time.

Unlike what happened in the past, the extra time won’t be added to the second game (the Redrock), which also needs to be completed in 35 minutes.

So, if you spend just, say, 20 minutes in the ecosystem building mini-game, you will still have 35 minutes for the Redrock.

At the same time, once the 35 minutes are over, you will automatically move to the Redrock.

The game will start with a short tutorial without a timer (you are welcome to go through that, but I will share the most important things to prepare in this article anyways).

You will be given two possible scenarios, a coral reef or a mountain ridge.

The scenario you get is overall irrelevant, as the logic to solve and win the game is the same, regardless of the environment you get (there are a few minor differences that I will cover in the FAQ at the end of this article).

Here is the Coral Reef scenario (source: my guide):

McKinsey Ecosystem Game Coral Reef

And here is the Mountain Ridge one:

McKinsey Ecosystem Game Mountain Ridge

So, we said that in this game you have to create an ecosystem that is sustainable and find a location. But what does this mean in practice?

During the game, they will tell you that you have to:

  • Identify 8 species that create a sustainable ecosystem and
  • Identify the ideal location where to place the selected species.

That’s it! 

If you read more complex things in other articles… well, forget about that. This is really what you will be asked to solve. 

(I have helped thousands of candidates with the problem solving game, so don’t worry. I have seen this over and over again).

You might think: “Whoa, that doesn’t seem that difficult if I have 35 minutes in total!”.

Well, it’s not so easy.

And to understand why, let’s see each of the tasks step-by-step.

Task 1: Selecting the 8 species

You will be given a set of 39 animals to choose from. 

These species are divided between producers and animals (source: my guide):

McKinsey Game Test Species

Specifically, the 39 species are divided into 9 producers and 30 animals.

Given you have to find only 8 species, this might sound daunting and easy to lead to information overload. 

However, don’t worry. As I will explain in a moment, you will actually need to select your 8 species out of only 13, if you follow the right step I will show you.

But first, let’s define what a producer (e.g., corals) is and what an animal (e.g., shark) is.

  • A producer consumes natural resources (e.g., “waste”, “sunlight”). It won’t need any calories to survive (we will see why that’s important in a moment). The natural resource consumed by a producer (e.g., “waste”) is irrelevant in terms of the game.
  • An animal consumes other animals or other producers. Some animals are not eaten by any other animals – in this article, I will refer to them as “Top Predators”. Animals will need calories to survive and can be herbivores, carnivores or omnivores.

Producers and animals are divided into three possible environments based on environmental conditions. Let’s call them Range A, B and C.

Some of these environmental conditions will be indicated in the label related to the various species.

Here is an example from my guide where you can see parameters such as depth, temperature, water current and salinity as parameters:

McKinsey Digital Assessment Conditions

Each species will have a few environmental characteristics like those mentioned above. You will find 2 to 4 characteristics for each species.

Each of the characteristics will be divided in the three ranges (A, B and C) that I mentioned before.

For example, for Depth, we might have the following ranges:

  • Range A: 31-60
  • Range B: 61-90
  • Range C: 91-120

Similarly, for Temperature, we might encounter the following ranges:

  • Range A: 28-30
  • Range B: 30.1-32
  • Range C: 32.1-34

And so on.

The division of producers and animals for the different environments is as follows:

  • For producers, you should have 3 of them in each environment. So 3 in A, 3 in B and 3 in C.
  • For animals, you should have 10 of them in each environment. So 10 in A, 10 in B and 10 in C.

Your final 8 species should all be from the same ecosystem.

Now you might say: “Wait, you said I have to choose 8 species overall, but in each environment, there are only 13!”.

Good catch! Now you can start to see how you can simplify the game solution.

The logic is actually quite simple.

You first have to understand which environment to choose between A, B and C.

And after that, once you are left with only 13 species, choose the 8 to build your chain.

But here is the tricky point that very few candidates know.

Not all the environments will allow you to build a sustainable ecosystem!

This means you cannot choose randomly between A, B and C and hope for the best.

You could waste a ton of time if you do so and exceed the 35 mins before you have your chain.

For this reason, I created an Excel Solver to identify in 30 seconds whether a selection could lead or not to a sustainable chain without the need to create the chain – you can get it for free with my course here.

Below you can find an example of a check done in just 11 seconds:

McKinsey Game Excel Template

If you don’t want to use specific resources like the Excel above, no worries.

I will provide a few tips later on to help you to find an optimal ecosystem anyway, so that you can still avoid a few traps in the game.

So let’s say that you have identified a range A, B or C, and the related 13 species.

How can you now select the 8 that make sense?

The answer is given by the variables called “food sources” and “predators”. Here they are, represented in the screenshot below:

McKinsey Imbellus Food Sources

Here is how the “food sources” or “predators” variables work.

Each species is linked to other species, as either food source or predator, to create a chain

The species will have some other species eating them (unless they are a top predator), and some species as food sources (unless they are producers).

In our example, Turtle is eaten by Big Eyed Fish and has Doughnut Coral as a food source.

However, that’s not the only thing you have to consider.

Indeed, as you can see, each species will have some calories provided and some calories needed.

McKinsey PSG Game Calories

The calories provided and needed are critical to understanding which of the 13 species you will have to select to find your ultimate 8 ones.

The way to understand how to use calories is simple: you have to follow the rules of the game.

During the tutorial, they will inform you about the eating rules for the chain. The most important ones are the following three:

  1. The species with the highest calories provided eats first.
  2. It eats the species providing the highest calories provided as a food source. In case of a tie, it will eat half from each of the two species with the same calories.
  3. Eating consumes calories from the food source by the amount needed by the predator. You need calories provided greater than zero for a species to survive and all calories needed equal to zero after they eat.

(If you are bit a confused, don’t worry, we will see an example in a moment).

After the first species has eaten, the next one with the highest calories provided will eat.

And so on.

So, yes, you need to be sure that the animals are connected to each other and that there is food chain continuity.

But you also need each animal to receive enough calories from its food source and that no species reaches zero in terms of the calories provided.

If a species doesn’t get enough calories or reaches zero with its own calories provided, the food chain won’t be sustainable, and most likely you will fail the game.

So how can you quickly create a sustainable chain?

Luckily for you, with my Excel solver, you can build the chain as well.

You can get this tool for free as well with my course here. In the course, I show you how to build a chain from scratch in less than 11 minutes.

McKinsey Imbellus Excel Template Pyramid

For those who prefer simpler solutions, in the course I also show how to build a chain from scratch using the templates I include for free.

McKinsey Test Practice Pyramid Template

If you don’t want or cannot purchase the course, no worries, I will explain a few tips below and also show some examples.

Task 2: Selecting the location

After having identified the 8 species, you will have to select the location where to place your ecosystem. 

You will be able to move the cursor on a map to find a location matching. 

Each location will have 7 to 8 possible conditions to consider.

In the below example from my guide you can see an example with 7 ones:

McKinsey Game Ecosystem Location

Only a few of these variables are relevant, however. The other variables are useless and are just there to distract you.

The relevant ones are those you found before, which were listed for the different species.

(Remember the previous screenshot for Turtle? The relevant variables were depth, temperature, current and salinity).

This task should not take too much time once you have properly selected the species in the previous step.

It will be sufficient to check the 2-4 variables of each species and find a location that allows matching the range of those 2-4 variables.

You can move the mouse on the screen and see on the top-right menu if the variables match the range of the 8 species you selected.

Ecosystem Game: example

Let’s see a concrete example of a working chain.

Let’s say you have selected 8 producers and animals and now it’s time to check if the chain you built during the game works. The following are the steps you want to take to verify that.

Say that the following is your chain. Assume that each line represents the connection between a species and its food source.

Solve McKinsey Game Ecosystem

Before looking at the solution, take some time to see if you can solve the chain by yourself. You can go back to the eating rules above and then solve the chain.

Done? Great! Let’s see if you got it right.

First of all, let’s see which animal eats first. Brown Hopper starts as it provides more calories.

McKinsey PSG Pyramid Template

Next, it’s time for Field Mouse to eat.

McKinsey Problem Solving Test Ecosystem

Now it’s the turn of Salmon Trout.

McKinsey Assessment Game Practice

Now it’s Red-Tailed Hawk‘s turn.

The McKinsey Game Solution

Finally, Brown Bear eats.

McKinsey Solve Game Tips

As you can see, all calories provided are greater than zero and all calories needed are zero. So, the chain works.

“That’s easy!” you might think.

Well, I agree. It is easy to check if the chain works.

The problem is, can you get to a working chain in time? Can you quickly display the information so that you can build a chain like the one above? And if the chain doesn’t work, can you move fast enough to a different chain?

That’s the challenging part and why I highly recommend you have a strategy and if possible a proven Excel tool to quickly identify your chain.

Additionally, some chains could be quite complicated, particularly when you have top animals eating most of the species. This makes it more difficult to understand if a chain works.

In my PSG simulation, you can find 3 different ecosystems of 39 species each with all the possible traps of the game

After that, I guarantee you will be ready for any scenario (and when I say I guarantee, I mean it! I refund every candidate who doesn’t pass the test).

Redrock Study - How does it work?

The Redrock is the new entry in the McKinsey game. It was introduced briefly in 2022, mainly in the United States. 

Starting from February ’23, it has replaced the usual second game of the Imbellus – Plant Defense.

The Redrock caused an important change in the PSG as the format of the game is different. 

During the Redrock, you will be required to perform several calculations – in particular percentages – something much more in line with the old McKinsey PSTs than the other problem solving mini-games.

The plot of the game is that you are sent to an island to perform analysis on the species present there (such as wolves and elks). 

The goal of your analysis is to make predictions based on data on the evolution of the population of animals.

In this game, you will have to complete 4 sections:

  1. The Investigation Phase
  2. The Analysis Phase
  3. The Report Phase
  4. The Case Phase

This last section (Cases) is new and it was not present in 2022.

You will have a time limit of 35 minutes to complete the 4 phases. Sometimes, you will have a small break before the following phase, although not always.

We will now analyze each of them.

Investigation Phase

In this initial part, you will receive a few paragraphs of text, including graphs and tables. 

You will be given an objective and based on that, you will have to collect the information on the right-hand side of the page for the following parts of the test.

The following is an example of the Investigation Phase (source: my guide):

McKinsey Redrock Investigation Phase

As you can see, you will have some parts of text in white. 

These are the pieces of information that you can drag and drop into your Research Journal (on the right-hand side) to be used for the following phases. 

There is a good amount of data that is useless and that you should skip. 

Once collected all the information, you will move to the following part – the Analysis phase.

Analysis Phase

In this part, you will have to answer 3 math questions (in some recent version, 4 questions). 

Each question will involve two separate parts, currently related to 2 different groups of animals. 

You will be given a calculator embedded in the game to perform the math and will be able to collect information from the Research Journal to answer your questions.

The following is an example of the Analysis Phase from my course:

Redrock Study McKinsey Analysis Phase

You can see how you can still have the Research Journal available and you can use it to answer the questions.

Once you have answered all the questions, you will move to the Report Phase

Report Phase

This part is structured into different sections: a written part and a visual one.

In the written part you will have to:

  • Answer 5 questions, based on your findings of the Analysis part.

In the visual part, you will have to:

  • Choose a graph and
  • Use it to represent the results of the analysis.

The following is an example of the Report Phase taken from my guide:

Redrock McKinsey Report Phase

Once you have completed the Report, you will move to the last section of the Redrock: the Case Phase.

Case Phase

This is the new part that McKinsey added to the game in 2023. 

You will have to answer 6 questions (it was 10 in the past, but McKinsey changed it, most likely because very few candidates were able to complete the game in time with that number of questions). 

The questions are unrelated to the analysis done prior to that moment in the Redrock.

The questions are not difficult but most likely require at least 2 minutes each. 

Most candidates mentioned it was difficult for them to complete the Redrock game in time.

The following is an example of the Case part from my guide, for the most difficult version with 10 cases:it

McKinsey Redrock Study Cases

As part of my course, you will be able to test your skills with 10 Redrock Practice Test questions, to simulate the same exact situation you will face during the Redrock Study case part.

Below you can find the initial screenshot. It is included for free with the course. 

You can check that this bonus is included in the course by clicking on the image below.

Ocean Treatment - How does it work?

In 2024, McKinsey launched a new game, called Ocean Treatment (the name might have some variations depending on the country – but the baseline of the game is the same).

This game is still in testing phase, so you might or might not find it the day of the test.

Currently, when it is present, you will play the Ecosystem and Redrock first, and then you will have to play this game.

In this game, they will inform you that you have to cleanse a section of the Ocean. To do this, you will have to select some microbes, according to specific rules.

The goal you will have is to select first 10 microbes and then, out of the ones you selected, pick 3 of them, according to the rules of the game, to cleanse the ocean.

You will have to repeat these steps for two different areas.

So overall, there will be 4 parts in this game:

  1. Selection of 10 microbes for Area #1
  2. Choice of 3 microbes for Area #1
  3. Selection of 10 microbes for Area #2
  4. Choice of 3 microbes for Area #2

You will have a time limit of 20 minutes to complete the 4 parts. Before each phase, you will have a small break that won’t be timed.

The activities you have to do in Area #2 are exactly the same as those in Area #1. Therefore, we can just focus on what you have to do in Area #1. The logic for Area #2 will be the same.

Let’s call Phase 1 the one where you select the 10 microbes, and Phase 2, the one where you choose the 3 microbes.

And now, let’s have a look at what each phase involves.

Phase 1: Selecting 10 Microbes

In this initial phase, you will have to select 10 microbes.

The rule to pick the microbes is that they will need to have the same parameters and characteristics of the area that you are considering.

You might think: “Wait, what are these parameters and characteristics?” 

No worries, I will explain it in a minute.

Each area is characterized by parameters, which are displayed within a range (think like “Rigidity: 4-7”) and characteristics (which are either present or not – example: “Hot”).

Below you can find an example of an area with 3 parameters (rigidity, liquidity, size) and 2 characteristics (hot and hydrophilic). You can find the parameters on the right-hand side, under “Area 1” (source: my guide).

Ocean Treatment Microbes

You will see the information about microbes appearing on the left-hand side, and you will have to pick 10 that meet the same conditions of the area. 

This initial part is pretty simple (at least with the current rules – they might change them while they continue the testing). You should spend a few minutes only to complete it. Then, you can move to the next phase, where you will have to pick 3 microbes.

Phase 2: Choosing 3 Microbes

This second phase, will require a bit more time. You will have to pick 3 microbes out of the 10, according to the rules displayed by the game.

The rules are pretty simple: the average of the parameters for the three microbes you have selected should be as close as possible to the average of the remaining 7.

The easiest way to do so is by using an Excel. I have created one specifically for this game, included for free with my course as well.

Below you can find an example of the selection process, with two microbes already selected.

After this, you will have to move to Area #2 and repeat the whole process again.

How should I prepare for the McKinsey Digital Assessment?

Ok, you have a clear idea of what to expect during the game. 

Now what? How can you be ready in the best possible way for the game?

Here are a few tips, divided among the three games.

McKinsey Game tips: Ecosystem Management

Tip #1: Choose the species first, then the location

I saw a lot of articles mentioning you should select the location first and then the species.

This is a terrible idea.


Very simple: as we saw, not all locations allow creating a sustainable chain.

If you choose the location first, you might end up trying to create a chain for a location where that’s not possible.

Indeed, as mentioned before, I created for you an Excel file that will automatically tell you if the species can survive or not in a given ecosystem.

So instead of starting with the location, start with the species first.

Once you have found a sustainable chain, finding the location will require little time – a few minutes if you know what to look for.

Tip #2: Use an Excel Solver

This is probably the #1 option you have to increase your speed during the Ecosystem building game.

If you don’t use an Excel file and solely rely on pen and paper, most likely you won’t have time to rebuild the chain if your first chain doesn’t work (and yes, as we saw before this could happen).

Having said that, be sure that the Excel is reliable. With my course, you will get 2 Excel Solvers, one of which can automatically tell you if your chain works within seconds.

Tip #3: Practice to finish a chain in max 15 minutes

Yes, you have 35 minutes for this game and time doesn’t roll over. So, you might say, why try to finish so quickly?

Because your first chain might not work.

As mentioned in this article, for some ranges of producers it is not possible to create a chain. Which means that you need to have time to rebuild one if needed.

If you are able to complete a chain in 15 minutes, you will have enough time to build a new one.

In my course, you can watch how I build a chain in less than 11 minutes.

So that you can replicate that on the day of the test and build two or even three chains if needed.

If you want you can then also test the approach with a proper McKinsey ecosystem simulation that you can add to the course.

If you prefer not to take the course, I would recommend looking for as many examples of chains online as possible, and replicate them in advance until you can spend a maximum of 15 minutes to complete even the most challenging ones.

McKinsey Game tips: Redrock Study

Tip #1: Review percentages

Most questions in the Redrock are related to math, particularly percentages.

So, it is a good idea to review them before the test. Think about “Given number X and Y, what is the percentage increase to go from X to Y?”.

These questions are relatively easy but remember, you will have limited time for each, especially in the final case section.

Tip #2: Review the Mean, Mode and Median definitions

Besides percentages, there are a few questions on mean, mode and median.

Although the questions are not difficult, if you forgot the definition of these terms, I would recommend reviewing them again.

Tip #3: Practice for the Case phase

The Case section is probably the one that determines whether you get your interview invite.

This is the part most candidates mess up.

The game is a lot more similar to the old PSTs tests previously used by McKinsey, and actually not at all “background neutral” like the Ecosystem Building or Plant Defense games. You need to be good with math to perform well.

The free option to practice with it is to use the old PST practice tests that you can find online. Although the PST is different, there are some similarities with some of the Redrock questions. 

If you want to practice with material closer to the actual game, I include a section specifically on drills for the Case phase as part of my course.

McKinsey Game tips: Ocean Treatment

Tip #1: Use an Excel file to pick the 3 Microbes

Given you have to work with 30 parameters in the second phase of the game (10 microbes and 3 parameters for each), I would highly recommend having an Excel sheet ready and using it to calculate the average of the parameters in that section.

If you want to save time building yours, I include one for free as part of my course specifically designed for that game and a data sample to practice for it in advance.

Tip #2: Allocate 50% of the time to each Area

In order to finish the game, you won’t have a predefined amount of time for each area, but 20 minutes overall.

Therefore, if you go long in Area #1, you might run the risk to not be able to finish the game on time.

I would recommend sticking to 10 minutes in the first Area, so that you have enough time to finish everything within the 20 minutes of this game.

Tip #3: Use the break between Area #1 and Area #2 to recharge

When you complete Area #1, you will have an untimed break (please ensure that it says “UNTIMED” at the top as this might change).

When you reach this step, you should have spent around 80 minutes since the beginning of the test (35 minutes for the Ecosystem game, 35 minutes for the Redrock, and 10 minutes for Area #1 of Ocean Treatment).

You will likely be a bit tired. Instead of moving right away to Area #2, I would recommend taking a few minutes to recharge and prepare for the last step of the game. You can also use the break to restructure your Excel (because you followed my tips and used an Excel sheet to pick the 3 microbes, right? Right?). So that you can have everything in place for your last sprint.

McKinsey Problem-Solving Game Practice

If that’s not enough, I have created for you the first and only video simulation with 300+ 5-star reviews.

(You can check the reviews on PrepLounge and on Trustpilot).

In the video simulation I will show you everything you need to know to prepare for the McKinsey Problem Solving game and be ready for the big day.

Here is a part taken from the Ecosystem section:

Here it is for the Redrock Study:

And here it is for the Ocean Treatment:

The best part? You will have a 100% money-back guarantee if you don’t pass the test if you purchase via this link (please note that I cannot offer the guarantee if you buy from any other website apart from

I have also created a full simulation to play for the Ecosystem and Redrock Games!

You will be able to play the games in advance with unlimited attempts and 3 different scenarios (Ecosystem), including the coral reef and mountain ridge, and all the 4 Phases (Redrock). 

Here is an example:

You can add the simulations to your cart during checkout here.

What about the old games of the Imbellus?

Honestly? I would not worry about them.

From the end of February ’23, every single test taker I heard from had the Ecosystem, Redrock and Ocean Treatment games, no exceptions.

Most guides and articles tell you to prepare for the old games simply because they have outdated information.

But if you really want to go the extra mile, I have added to my guide how to prepare for the Plant Defence game as well (it’s included for free – no extra payments needed).

You will also find two full plant defense maps and many tips on how to prepare in the best possible way for the different mini-games.

Okay, okay, I hear you.

You want to know more about the games that appeared in the past anyway, right?

As mentioned before, the “old games” are plant defense, disaster management, disease management and migration management.

Let me present them to you below.

1) Plant Defense

This was the most common second game until February ’23.

In the plant defense mini-game, you had to defend a native plant from the attacks of the invasive species. Your goal is to resist at least 15 turns in 3 maps, the more the better. 

Unlike other games, the gameplay is based on alternating turns between you and the opponent (the computer), much like a traditional board game.

Here is a screenshot of the game (source: my course):

McKinsey Plant Defense Strategy Map

For each map, the recommended time is 12 minutes, for a total of 36 minutes.

You can spend more or less time on each map, however at the end of the 36 minutes the game will automatically come to an end.

Maps are independent of each other, so the performance in map #1 won’t have an impact on maps #2 and #3.

As you can see, you will have a plant at the center of the map.

Plant Defense Game McKinsey

You will have to protect the plant from the invaders that will appear during the game. If the plant is reached by an intruder the game is over.

If you reach less than 15 turns in 2 maps or more, most likely you won’t pass the game (I have helped candidates who scored below 15 in one map and passed anyway).

On the sides of the map, as the game progresses you will see invaders coming (in this example: 90 rats).

McKinsey Plant Defense Invader

Every 2-3 turns you should see one. You will see a yellow line connecting the foxes/rats to the plant – that’s the path they will follow to reach it.

Invaders will move one square per turn, until reaching the plant (if not killed by your defenses before that).

The types of animals that might attack the plant include rats and foxes.

Each invader species could be affected differently by the barriers that you will be able to place.

The game is played on a map divided into multiple squares (think of it like a grid of 10×10 to start). The map size increases when you move to the second and then the third map.

In order to resist as long as possible, you can do 2 things:

  1. Place defenders (e.g., wolves, eagles) to inflict damage on the invasive species or
  2. Delay invaders by placing terrain (e.g., rocks, forests, cliffs).

You will be able to use three different types of terrain: rocks, forests and mountains, each with specific characteristics (you can find more information on that in my free guide available with the Solve Combo course). A terrain might be able to delay only a specific type of invader.

The defender can be of different types. Examples include snakes, wolves and eagles. Each defender will have a different range of attack (i.e., how many squares on the map they can cover) and inflict different damage.

Sometimes the strategy involves the placement of both defenders and terrain. Indeed, you may need to place a terrain in order to be able to place a specific invader that can be used only on that terrain.

You will be able to place a maximum of one defender and one terrain on a specific square.

As I told you, this game is divided into three maps. In each of the maps, you will play 15 turns.

At the beginning of turns 1, 6 and 10, you will have to place your resources for the following 5 turns.

Maps 1 and 2 are slightly different from map 3.

  • In maps 1 and 2, once you reach turn 15 (or once the invader reaches the plant), the map will end and you will move to the next one.
  • In map 3, you will still be able to play until turn 15. However, the game will continue after that – meaning, invaders will continue to arrive until they reach the plant. Ideally you want to have resources that can defend you for a long time after that, because the longer you resist, the better.

You can also adapt your strategy and edit a resource (defender or invader), as long as its turn to become active has not passed yet.

So, if you are in turn #3 and you placed say a barrier in turn #4, you can change it. However if you put a defender in say turn #2, you cannot edit that anymore.

Unlike other parts of the Imbellus, this is a turn-based game. Meaning you will play first, then the computer, then you etc.

The game also requires you to follow some rules. The most important ones are:

  • You might only be able to place a defender on a square with a certain terrain.
  • You might only be able to place a terrain close to another terrain.

Some key tactics to follow are:

  1. Place defenders/barriers close to the plant first.
  2. Focus on killing visible invaders first, then use the resources to increase the defenses around the plant.
  3. Structure the defenses so that you can resist after turn 15 in the last map, as extra turns will count for your final score, even if you won’t be able to move.

As mentioned, you don’t need to prepare for this game anymore.

But if you really want to go the extra mile, in my Combo I include 8 videos and 1 hour of content with every single detail on this game and 2 map simulations.

In the video simulation, I show how to resist 25+ turns instead of the recommended 15.

It is included for free with the course so you don’t have to pay extra for it. Here is a quick extract of it:

2) Disaster Management

The disaster management mini-game appeared at the very beginning of the Imbellus. It was quickly replaced by the others – so McKinsey probably didn’t find it useful to screen candidates.

This game has NOT been used in the last few years.

In this game, you have to (i) identify the type of disaster affecting the island and (ii) move the animal population of the island to a different location to allow the survival of the species and avoid their extinction, following the disaster.

To identify the disaster, which could include volcanic eruptions or tsunamis, you have to use environmental data provided during the game.

Here is a screenshot of the game (source: my guide):

McKinsey Online Assessment Disaster Management

There is not much information available on this game. However, the technique to use is most likely similar to the one of the Ecosystem Building mini-game variation in terms of checking resources to allow survival. 

Possibly this is why McKinsey didn’t use this game much –  it might not have been mutually exclusive with the Ecosystem game.

You don’t need to worry about this game as it is not used. If it comes back, I will update the article right away so you will know.

3) Disease Management

This mini-game last appeared in 2021.

You will be presented with a disease within an ecosystem. During the game, you have to identify the rules of an infection and which animals will be affected next. 

This game has NOT been used in the last few years.

Here is a screenshot of the game (source: my guide):

McKinsey Imbellus Game Disease Management

During the game, you will see three different time phases. In each phase, you will see some details related to the animals (represented by circles). The details include weight, name of the animals and health status.

The key is to move between the different time slots to try to predict the pattern and thus which animals will be affected next and complete the disease diagnosis.

This game is not used anymore, so you don’t need to spend time trying to learn how to do well with it. But if you are curious, I include the tips for that as well in my guide.

4) Migration Management

In this mini-game you have to lead a group of animals towards different maps, with the goal of having as many animals as possible to survive and reach a defined destination. 

This game has NOT been used in the last few years.

Here is a screenshot of the game (source: my guide):

McKinsey Imbellus Game Secrets Migration Management

There are 13 different maps with increasing difficulty. You start the game with a certain amount of resources and of animals. 

Whenever you move on the map, you can either increase or decrease your resources and collect additional animals according to the location you end up in, which impacts the number of animals that will survive.

You can learn only partial information on the effect of moving to one of the slots on the map before reaching it – specifically, you know the resource present there, but not the amount. Additionally, you can use some multipliers (e.g., x2, x4) to increase the number of resources achieved once you reach a slot.

The main complication of the game is that you don’t know how many resources you will receive once you reach one of the points on the map. 

The key tip to pass this game is to assume you will get the AVERAGE amount of the resource there.

To calculate the average, simply take the number of resources you get after the first 2-3 initial moves and use the average of that from then onwards.

With that assumption in mind, you can find the path that allows you to get the highest amount of resources and the fastest path to the final exit point.

There is no need to focus on this game anymore as it is no longer used.

Wait! I have a ton of other questions on the Solve Assessment...

Need more help? Don’t worry, I have compiled for you some of the most common questions about the game below. Let’s get started!

1) I read there are two types of scores (product and process ones). How should I take that into account?

If you have read a few other articles, you might have come across the information that McKinsey evaluates both the process and product scores.

The product score is related to the final outcome, such as the answer you submit.

The process score is related to your actions during the game, such as mouse clicks or keystrokes. 

For example, in the Ecosystem Building scenario, the product score is based on how many species survive and whether the ecosystem is sustainable. In the Redrock scenario, the product score is related to the information dropped in the Reaserch Journal and the answers provided in the Analysis, Report and Case sections.

The process score is related to your interaction with the elements present during the test. The game measures for example:

  • Where you click.
  • How much time you spend on different parts of the game.
  • How much time you spend from the information provided to take action.
  • How much and how fast you scroll through the information provided.

Here is a quick sum up as general outline:

Score type What is tested Example
Product score
Do you reach the correct final result?
Final ecosystem submitted
Process score
Do you reach the final result in the most efficient way possible?
Clicks and time taken to reach the final ecosystem submitted

McKinsey claims that both scores will have an impact on your performance.

My personal suggestion on how to approach this?

Simply ignore the process score.

You have no real control over it and no one knows exactly how it is calculated (although some guides claim that they know to push you to buy 😅).

The only thing I would recommend paying attention to is to avoid clicking randomly on the screen as we don’t know how it might impact the score. However, I assume you would have not done so anyways ;).

2) Will I have to take the game at home?

Yes. After COVID, McKinsey has become very flexible in offering the game to be played in different locations. 

This is actually one of the reasons why they moved from the PST to the PSG game – to provide more flexibility and reach more candidates with minimal effort.

3) How do I know if my McKinsey office has the game?

In the past, depending on where you live, McKinsey may or may not have offered the game as the first step of the recruiting process. 

Now, to the best of my knowledge, all offices use the PSG game. In any case, you will receive an email from McKinsey confirming that you will have to play the game.

4) Will I receive a score for my performance after the McKinsey Online Assessment?

Usually you don’t receive a score but rather a confirmation of whether you passed the game or not. However, you can request to HR the score and your score percentile, which represent a benchmark compared to other candidates.

5) I have to take the McKinsey Game, but I found information online about the Imbellus, the PSG and the problem solving game. Are these games all the same?

Yes. Initially McKinsey referred to the game as “Imbellus”, named after the company that created the test. However, McKinsey then officially renamed it “Solve”. 

The game is also known as the Problem Solving Game (or PSG, from the initials) or McKinsey Digital Assessment game.

Some candidates also refer to the game as the McKinsey Problem Solving Test or McKinsey PST, although technically that refers to the old test with 26 questions that McKinsey used before introducing the game.

6) Why is the test also called “Imbellus”?

The McKinsey game was developed by a company called Imbellus. One of their first clients was indeed McKinsey, for which they developed the game.

For this reason, the game itself has been nicknamed “Imbellus”. Even after McKinsey rebranded it as the “Solve” game many people still refer to the test by its the old name.

The company Imbellus was acquired by Roblox in 2020.

7) I am applying to McKinsey Digital / Operations / Implementations. Will I have to take the test?

Yes, the McKinsey PSG is used for all the divisions currently, so you need to prepare for it.

8) Is there any simulation of the McKinsey Imbellus test? What is the best McKinsey game practice tool I can use?

Yes. I have created a simulation of the Ecosystem and Redrock games for you. You will have lifetime access to them, and you can play them unlimited times.

You can add it at checkout using this link. Furthermore, it comes with a 100% money back guarantee if you don’t pass.

Once you have played the simulations, I guarantee (and I mean it!) that you won’t have any surprise during the game and you will have all the tools to ace the McKinsey test.

9) Is the webcam working during the McKinsey’s Solve test? Can they see candidates playing?

No, your webcam won’t be needed for the game and it won’t record what you do at any time . The audio won’t be active either.

During the game, they will only monitor your clicks on the screen as part of the so-called “process score” (which as mentioned above you can ignore and just refrain from clicking randomly on the screen).

10) My friend took the problem solving game and told me the correct chain for the ecosystem. Can I just use it?

No, because the ecosystem game doesn’t have the same species/chains and changes each time you play.

The chain your friend used might not work even if you have the exact same animals.

11) Should I practice video games to prepare?

You might have read somewhere that you should play strategy games like Sim City and Age of Empires for the Ecosystem Game (and when the plant defense game was used, several tower defense games such as Plants vs Zombies or even turn-based puzzle games).

Some video games might help a bit to improve your decision-making skills and practice mini-games similar to those you will have in the PSG.

However, the marginal utility of playing them might be very low if you are already familiar with video games.

If you really want to play games to prepare, I recommend using a simulation of the actual games and prepare with that.

12) How does the game look like?

The picture in this article should give you a good idea. Additionally, the following official video from McKinsey shows some parts of the game.

Keep in mind that some of the screenshots are outdated. For example, species used to have a number of individuals reported, but that’s no longer the case (each species now counts as one).

In my course, you will just see the most updated visuals of the current games.

13) Does everyone get the McKinsey problem-solving game? I am an experienced hire, do I have to take the test?

All candidates I have helped with up to 10 years of experience had to take the PSG, so if you are in that range most likely you will need to play the Imbellus.

14) What if I get a different mini – game?

As of today (when you read this as I update this article in real-time whenever there is a relevant update), the games are still Ecosystem, Redrock and Ocean Treatment. 

If you still want to prepare for the others, you can find a detailed description and tactics to follow for all six major games in my PDF guide included for free with my course.

15) I received the test invitation. Does this mean I have passed the CV screening?

Not necessarily. 

In some cases, McKinsey performs the resume screening after the test. Therefore, receiving an invitation for the problem solving game from McKinsey doesn’t necessarily mean you cleared that part.

16) How important is the McKinsey Game?

McKinsey reported that they evaluate the game together with your application materials (CV, cover letter and referrals).

Most likely you need to both have a minimum score AND a good CV/cover to pass to the next round and move to the McKinsey case interview stage.

So, a good performance on the test is necessary but not sufficient to move forward in the recruiting process.

17) Do interviews take place only after the McKinsey assessment?

Yes, you have to take the test first before moving to the next phase (the McKinsey personal experience interview and case parts).

The game is the first step in the McKinsey recruitment process, either together with or right after the CV screening.

18) How much time do I have to complete the test?

Usually candidates must complete the test within one or two weeks. They will inform you about the exact amount of time when you receive the invitation email from McKinsey.

19) Why did McKinsey change the test from the PST to the PSG Game?

There are a few reasons why McKinsey switched to the PSG Game in their recruitment process. In my opinion, the most relevant ones are:

  1. Scalability. The test can be taken at home, meaning they can send it to anyone now. This can help McKinsey to reach more candidates.
  2. Recruiting efficiency. Being the whole process digital and the whole score represented by a number immediately available, it takes less time to evaluate candidates. Plus, McKinsey can send the test even before a CV screening, saving even more time in the recruiting process.
  3. Test effectiveness. A digital test can be used to collect more data points, measuring both the final number and how a candidate arrived at that number. This should (at least in theory) offer more insights into the decision-making process of a candidate and whether someone might be suitable for a job as a McKinsey consultant or not.

In the past, the digital assessment was also agnostic in terms of the business knowledge and background of the candidates, although this component is now partially gone after they added the Redrock Study, which has a strong math component.

20) I read that there are multiple skills tested by McKinsey in the test, such as system thinking. How can I prepare for each of these?

The best way to prepare is to play the game in advance (or learn the steps to follow in advance to create the right ecosystem) and to prepare for questions similar to the one of the Redrock Study.

In theory, you could try to develop skills for each of the five areas they evaluate, which McKinsey calls cognitive traits. 

These traits should reflect your thinking skills, problem solving skills and the related evaluation criteria when dealing with complex problems. 

The game is designed to test these skills and your ability to solve problems and take the best course of action. 

I have listed below for you the skills that McKinsey tests in the game.

Skill Element analyzed
Critical thinking
Can you derive rational conclusions from facts?
Can you make the best decision with multiple options available?
Can you absorb information fast?
Situational awareness
Can you understand the relationships between different factors?
Systems thinking
Can you determine relationships of cause-effect?

(For those who are a bit nerdy, you can find the full description of the skills from the research paper explaining the McKinsey Game skills tested – no need to go through it though as it won’t help with the game).

Overall, I think you would be better off playing the game in advance rather than trying to focus on the skills tested.

21) What is the McKinsey digital assessment pass rate?

No one knows the exact metric but usually these tests can screen out up to 70% of the candidates. In any case, please keep in mind that they will assess your CV and application materials together with your performance.

22) What is the best way to prepare for the game?

I am biased on this because I created a course exactly on the game 😉 You can find it here.

I can provide you with three good reasons why I think my course is the best resource to prepare:

  1. If you don’t pass the test within 60 days of the purchase, I will refund 100% of the course. Just send me the email indicating you have been rejected due to the test.
  2. The course has 300+ 5-star reviews on Trustpilot and PrepLounge
  3. Even if you don’t pass the test and receive a refund, you can still keep all the included bonuses, such as the 62-page Industry Cheat Sheet or Excel solvers.

Plus, if you want you can also add the game simulations at checkout and play with the Ecosystem and Redrock games as well.

23) Is there any difference if I get the coral reef or mountain ridge game scenarios during the Ecosystem game?

The only differences I have been notified about are that:

  • The total variables of the location are 7 in the coral reef and 8 in the mountain ridge.
  • Species have 2 variables relevant to the location choice in the coral reef and 4 in the mountain ridge.

Both points are irrelevant in terms of the logic to follow based on the tactics described in this article. So overall, the difference is mostly in the graphics of the game.

In my simulation I let you play with the highest possible number of variables so that you can face the most complex situation overall.

24) I saw several screenshots of the ecosystem game including the number of species. Is this a new version of the Digital Assessment?

Most likely you have seen something like the following, taken from the McKinsey video:

McKinsey Problem Solving Game Practice Ecosystem

This is the old interface version of the game and it is no longer in use. In the current test format, there are no numbers for the individuals of the  species. So, you don’t need to worry about the number of species now.

Are you ready to play the McKinsey PSG?

Hope you are now well-equipped with a good overview and the right strategies to pass the McKinsey game.

If you want to go the extra mile with the preparation, have a look at my full video simulation, which comes with $180+ in bonus materials, including a 153-page PDF guide, 2 Excel solvers including an algorithm to build the chain automatically and a 62-page industry cheat sheet to prepare for the interviews as well.

Plus, now you can also play the Ecosystem and Redrock games if you want! I have created for you a complete simulation of the game to play with unlimited usage which you can add to the Combo as well 😉

Ah yes, and you will get a 100% money-back guarantee if you don’t pass within 60 days. Just send me the rejection email of the test and I will refund the course.

The only reason I can offer this is that I know the course works and you will pass the McKinsey Digital Assessment and move to the case interview stage.

Right now, I have an 89% success rate (if you come across comparable claims: ask them why they don’t offer a full guarantee ;)).

Click here to access the course immediately and join the hundreds of successful candidates I have helped and who got offers from McKinsey.

Any questions? Drop me a message and I will reply within 12 hours.

Francesco Rieppi

Founder of PSG Secrets, entrepreneur, case interview coach


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7 months ago

Good luck, everyone! Long read, but definitely the best free guide out there – helped me pass the game and make it to the interviews

Reply to  Scott
5 months ago

Hi Scott, do you have any tips on how to go about working out which animals fit in the chain once youve gotten down to 13?

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