Playing Through a Simulation Step by Step

Walk a simulation forward one round at a time and make a decision in each round — like a board game. Works in the editor, in the Reader and on published sites.

Most simulation dashboards show the whole timeline at once — change a slider and every chart redraws from start to finish. Play mode works the other way round: you walk through the simulation one round at a time, decide something in each round, and only see what happens next once you get there.

This turns a twin into a game, a training exercise or a planning drill. The best way to understand it is to play one.

Try it: the Beer Distribution Game

The Beer Distribution Game template comes with a ready-made dashboard called Single Player Game. You are the retailer in a four-stage beer supply chain. Each week you see what your customers ordered and what arrived from your supplier — then you decide how much beer to order.

1. Click Start on the round control. The dashboard jumps to round 1.
2. Read the tiles: Incoming Order, Incoming Delivery, Inventory, Backorder, Cost.
3. Type your order into Your Order. The round control marks it staged — entered, but not yet committed.
4. Click Step. The round is committed, every tile updates, and you move on to the next week.
5. Keep going until the round control says Run complete. Now the charts appear — and you see how your decisions rippled up the supply chain.

Watch the Backorder tile: it turns red as soon as your backorder goes above 500 units.

The round control

Before a run, the round control shows a single Start button. During a run it shows:

• Round 3 / 24 — where you are (on a twin with a calendar, the date too)
• Step — commit this round's decisions and move on
• Back — go back one round (only if the dashboard allows it)
• Restart — back to round 1, discarding this run's decisions
• End — stop playing and return to the normal dashboard view

Playing in the editor vs. playing as a reader

Where you play decides what happens to your decisions:

Where you play	What happens to your decisions
Editor (you can edit the model)	Saved into the model, in the parameter set the round control names. The play-through becomes a record you can compare with other runs.
Reader or a published site	Kept in your browser only. Nobody else sees them, the model does not change, and reloading the page starts a fresh game.

So a published dashboard is a safe game to hand to anyone: every reader plays their own copy.

Careful in the editor: Start and Restart clear the decisions the previous run recorded in the target parameter set. Give play its own parameter set — the Beer Game uses one called game — so you never overwrite a set you want to keep.

Leaving and reopening a dashboard always starts again at round 1. Committed rounds stay in the parameter set; you just walk through them again.

Building your own playable dashboard

You need a simulation diagram with at least one input and one Round control.

1. Make an input a round decision

Select a slider and, in the Properties panel, set Writes to to Round decision. Instead of changing the value for the whole run, it now records a decision for the current round only. Set Input style to Number field if players should type an exact amount. Outside a run, the control says Start play mode to use this control.

2. Add a round control

Drag Round control from the Toolbox onto the diagram. In Properties:

• Write decisions into — the parameter set that receives the decisions when you play in the editor
• Allow going back a round — shows the Back button. Games usually leave it off; modellers stepping through a twin usually want it.
• Confirm before committing — Step asks Commit this round? and needs a second click
• Played as a game — offers the Game button in the top bar, to run this dashboard as a multiplayer game

3. Show the situation with value tiles

A Value tile shows one number. Useful settings for play:

• Reads — Latest result follows the game; One round earlier shows last round's value
• Show change vs. previous round — adds a small up/down difference
• Show the round being decided — shows the current round before your decision is applied, e.g. this week's incoming order. A tile that depends on the decision you are still making shows pending.
• Conditional colour — colours the tile when its value crosses a limit. Click Add rule, choose a comparison, a Limit and a colour. Rules are checked top to bottom; the first that matches wins.

4. Decide what charts reveal

Each chart and value tile has a During a run setting:

• Reveal round by round (default) — the chart grows as you play
• Hide until the end — the chart shows Revealed at the end of the run until the last round is committed. Use this for the "how did I do?" charts, so players decide from what they would really know.

5. Publish it

Embed the dashboard in a publication and readers can play it without an account. The Beer Game's publication is simply the Single Player Game dashboard on its homepage.

Good to know

• The number of rounds is the number of timesteps in the scenario.
• The round control's other actions (Submit round, Advance round) belong to multiplayer games and show Needs a multiplayer session on their own. Use Step. To let several people play together, see Running a Multiplayer Game.

Next steps

• Adding Charts, Sliders, and Checkboxes — the widgets a dashboard is built from
• Creating Twins and Scenarios — parameter sets, and where rounds come from
• Running a Multiplayer Game — let several people play the dashboard together