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Goldratt's Dice Game: Free Bottleneck Simulator

The matchstick-and-dice game from "The Goal", with 5 scenarios and a 500-run comparison. Keeps working without internet once loaded.

Works on Windows, Android, iPhone, and Mac.

Nothing leaves your browser — no sign-up, no tracking.

How to play & why it matters
  1. Roll. Each station rolls a die and moves up to that many matchsticks downstream.
  2. Watch the piles. Inventory builds in front of the slow station; output falls below 3.5 per turn.
  3. Compare scenarios. Run 500 games per scenario on the same dice and see which change actually raises throughput.

Why it matters: Dependent events plus statistical fluctuations mean a station cannot pass on more than it received, so lost capacity upstream is never recovered. That is why balanced lines underperform.

Five focusing steps → scenarios: Identify → "Herbie" (slow station, die 1–3); Exploit / Elevate → "+1 at the bottleneck"; Subordinate → "Drum-buffer-rope"; Do not optimize non-constraints → "Mirage"; Repeat → constraint moved after Elevate.

Two conditions drive every factory, team, or project: dependent events (you can only pass what you already have) and statistical fluctuations (output varies every turn). Together they explain why throughput, inventory, and operating expense diverge — and why the constraint sets the pace for the whole system.

Scenarios

Production line

What you are seeing

    Cumulative output

    Inventory between stations

    Compare scenarios (Monte Carlo)

    Compare pairs: Mirage vs Herbie — speeding a non-bottleneck adds WIP, not throughput. Exploit raises output. Drum-buffer-rope is roughly in line with Exploit on throughput (its edge comes mostly from the pre-filled buffer) with far less inventory. All five runs use the same dice sequences.

    Five scenarios in this simulator

    1. Balanced line

    Every station uses a fair die (1–6). Average capacity is 3.5 per turn, yet finished output is lower — variability stacks through dependent steps while excess upstream work becomes piles, not sales.

    2. Herbie (identify the constraint)

    Station 3 rolls 1–3 only — the "Herbie" from The Goal. Watch inventory accumulate in front of it; system output cannot exceed what this station can process.

    3. Mirage (do not optimize non-constraints)

    Speed up station 1 while the bottleneck stays at station 3. Throughput barely moves; WIP grows upstream of the real constraint. Extra capacity off the bottleneck is a mirage.

    4. Exploit / elevate (+1 at the bottleneck)

    Add +1 to the bottleneck die (+1 effective capacity — it can still idle when starved upstream). Throughput rises because you changed the constraint — compare with Mirage on the 500-run table.

    5. Drum-buffer-rope (subordinate the rest)

    Same +1 at the bottleneck, plus rope release and a pre-filled buffer before it. Throughput is roughly in line with scenario 4 (the buffer helps early on), but inventory in the line drops sharply — the classic DBR trade-off.

    Frequently asked questions

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