PSG vs Solve vs Imbellus — what they all mean
The McKinsey assessment has had three names in roughly seven years. None of them changed the underlying test much, but the naming has confused every cohort of candidates since.
Imbellus Assessment (≈ 2017–2020)
The original. Built by a vendor called Imbellus, the test featured the Ecosystem Building game (8-species food chain, calorie balance) most candidates remember from old YouTube playthroughs. McKinsey acquired Imbellus in 2020 and rolled the test into its own assessment platform.
Problem Solving Game / PSG (≈ 2020–2024)
The first McKinsey-branded version. "PSG" stuck in candidate communities and search behaviour even after the official name moved on. The mini-game lineup evolved during this period — Ecosystem Building stayed, Red Rock joined, Plant Defense was retired.
McKinsey Solve / Digital Assessment (2024+)
The current official name. The 2024 format introduced the Sea Wolf game (microbe selection across 3 ocean sites) and Sustainable Future Lab. In early 2026 the legacy Ecosystem Building game was retired, leaving the active three: Sea Wolf, Red Rock, and SFL.
What the 2026 PSG actually contains
Three mini-games, roughly equal weight, played back-to-back inside a single ~70-minute proctored session. Each game has its own mechanic and its own failure modes. A useful PSG simulation covers all three — not just the famous one.
What a realistic PSG simulation needs
Most things online labelled "PSG simulator" miss at least two of these. Before paying for any tool — or trusting any free one — check it against the four criteria below.
Matches the 2026 format
Covers Sea Wolf (microbe selection), Red Rock, AND Sustainable Future Lab — not the retired Ecosystem Building food-chain game. If a tool still leads with Plant Defense, the Imbellus food-chain Ecosystem, or 2019 screens, it's stale.
Browser-based, proctor-similar
The real assessment runs in-browser with a proctor extension. A useful sim runs in your browser too — not a PDF download, not a video walkthrough. Click targets, drag-and-drop, calculator panels should feel similar.
Per-game scoring feedback
A score number alone is useless. You need to know which traits you mis-picked in Sea Wolf, which exhibits you misread in Red Rock, which judgment dimension you under-weighted in SFL. Without per-game diagnostics, you can't improve.
Fresh seeds across reps
If you can memorise the answer set after one attempt, the tool stops teaching you. Real value comes from varied species pools, varied case prompts, and varied SFL scenarios across reps.
Time and scoring per mini-game
| Mini-game | Duration | Weight | What to drill |
|---|---|---|---|
| Sea Wolf | ~30 min | ≈ 1/3 of total | Trait recognition, attribute-range arithmetic, microbe categorization speed |
| Red Rock | ~35 min | ≈ 1/3 of total | Exhibit reading speed, calculator discipline, hypothesis structure |
| Sustainable Future Lab | ~20 min | ≈ 1/3 of total | Stakeholder balance, judgment under ambiguity, 4-pillar awareness |
The weights aren't officially published, but the working assumption — confirmed by enough candidate score breakdowns to be reliable — is that the three games contribute roughly evenly. Which means under-drilling Red Rock because Sea Wolf is more fun directly costs you about a third of your potential score.
Where free PSG simulations fall short
Free PSG content is abundant and mostly unhelpful. Three honest categories:
- YouTube playthroughs of legacy Imbellus. Useful for the 30-second "oh, that's what it looks like" moment, useless beyond that. The format on screen isn't what you'll sit. Don't drill against it.
- Free demos that gate scoring. Common pattern: you can play, but the results screen is locked behind a paywall. You learn nothing from a play you can't review.
- Forum-built mock simulators. A few exist, usually for Sea Wolf only, usually with 2020-era species pools. Better than nothing for one diagnostic pass, but won't move scores meaningfully.
The exception is the free tier on SolvePrep: one full play of each of the three 2026 mini-games, with the actual scoring breakdown, no credit card. It's specifically designed as the diagnostic pass that tells you which game to drill.
See the full free PSG breakdownHow to actually practice the PSG simulation
Three steps. Don't skip step one — almost everyone wants to and almost everyone regrets it on test day.
1. Diagnostic pass on all three games
One full play each of Sea Wolf, Red Rock, and SFL — with a real score at the end of each. The point isn't to do well; it's to find out which game is your weakest. Most candidates discover they're worse at Red Rock than they assumed.
2. Allocate runway to the weakest game
If you have 7+ days, give roughly half your remaining reps to your weakest game and split the rest. If you have 3 days, give two-thirds to the weakest. The 7-day prep plan has the full breakdown.
3. Drill timed reps with review
Every drill rep must be (a) timed and (b) reviewed afterwards using the per-game feedback. Untimed reps build false confidence. Unreviewed reps don't move scores. Keep going until your weakest game catches up to your strongest.
Frequently asked questions
Is the McKinsey assessment still called PSG?
Internally and in older candidate communities, yes — PSG (Problem Solving Game) is still used. Officially, McKinsey has rebranded it to the McKinsey Solve assessment as of 2024, and it's also referred to as the Digital Assessment in some regions. They all describe the same test. The 2026 format contains three mini-games: Sea Wolf (microbe selection across 3 ocean sites), Red Rock Study, and Sustainable Future Lab. Note: the older Ecosystem Building game (food-chain / calorie balance) was retired from the active rotation in early 2026.
Where can I practice the McKinsey PSG simulation free?
SolvePrep offers one free play of each of the three mini-games on the 2026 format — no credit card required. That's enough for a diagnostic pass. Other free options (YouTube playthroughs, old Imbellus simulators) exist but mostly cover the retired 2019 format and teach habits you'll need to unlearn.
How realistic are paid PSG simulations vs the real assessment?
A well-maintained paid simulator (one updated for the 2026 mini-games) is roughly 85–90% realistic on the underlying mechanics — trait matching, exhibit reading, microbe attribute ranges, situational judgment scoring. The remaining gap is the proctored environment, the polished UI, and the live time pressure of a real test slot, none of which a browser sim can fully replicate. Reps still transfer.
Can I retake the McKinsey PSG?
Each application cycle typically allows one Solve attempt. If you don't pass, retaking generally requires reapplying — usually after 12–24 months depending on office policy. This is why practice sims matter: you don't get a do-over inside the same attempt.
Does practice with a PSG simulation actually move scores?
Yes, but mostly through pattern fluency — recognising trait combinations in Sea Wolf, exhibit structures in Red Rock, and stakeholder dynamics in SFL fast enough to act inside the clock. Untimed reading of the format alone doesn't move scores. Timed simulator reps with post-game review do.
Start your PSG simulation diagnostic
One free play of each of the three 2026 mini-games. No credit card. After the diagnostic, the same account unlocks unlimited reps and per-game review on the Elite tier.
Keep going
- ← Back to the McKinsey Solve guide hub
- Sea Wolf guide — the 20%-per-undesired-trait scoring rule
- Red Rock guide — where most candidates actually lose points
- Sustainable Future Lab guide — situational judgment scoring
- Free McKinsey PSG simulation — what's actually free in 2026
- Best McKinsey Solve prep tools 2026 — honest comparison