YOUR FIRST SHIFT
Follow the flow.
Buy takes shares from the asks. Sell trades into the bids. A large order can exhaust available quotes; its remainder is cancelled. New offers arrive as agents react.
Limit orders wait at your chosen price. Click a book price to set one, then choose Buy or Sell. Cash or shares are reserved until filled or cancelled. Orders use price, then arrival time priority.
Pause freezes the other agents. You can place an order while paused and step forward to study their response. Press Space to pause or resume. Time labels are simulated.
Pace defaults to 0.25×: one market second takes four real seconds. Choose 0.1× for closer study, or increase the speed any time. The two pacing checkboxes control pauses for order preparation and new contact or news messages. Resume explicitly when you are ready; submitting an order does not restart the clock.
Shorting is available in Unlimited sandbox. Sell / Short reduces a long position or opens a short once you sell beyond your holdings. Buy / Cover reduces a short, then opens a long if you buy more than you owe. Close position trades toward zero. Practice mode is long-only.
Equity is your cash balance plus the signed value of your position at the current midpoint. Total P&L combines realised and unrealised results after fees. Unlimited mode starts its ledger at $0 with unlimited credit; practice starts with $250,000. A short has negative position value and positive sale proceeds in cash.
Messages arrive in a floating bubble. Open the inbox (I) to read your desk messages and news wire. The market signals panel contains only observed price and depth alerts. Messages can be partial or uncertain. Private valuations and maker positions stay hidden until you end the session.
Unrealised P&L uses the current midpoint. It is not a promise of what you can realise by selling. Market-taking fees are 0.02%; resting fills have no fee in this prototype.
Unlimited mode permits cash borrowing without a funding limit and short positions up to 100,000 shares. It does not create counterparties. Practice mode starts with $250,000 and does not permit short selling.
Session length can be 10, 30 or 60 simulated minutes. Each ten-minute block develops a new event chain. Your positions, orders and all agent accounts carry forward. Choose a chart window from five minutes to the full history. The shaded lead-in contains real simulated trades. Positions, entry prices, losses and outstanding orders carry into your session.
Other traders have finite cash and shares. Most can short using limited borrowing and collateral. Their habits range from patient and disciplined to impulsive and stubborn. Losses reduce their capacity, and stressed accounts attempt to unwind using available liquidity. Covering a loss does not restore their capital.
Order programs (P) let you work an iceberg, TWAP, price ladder or target position. An iceberg displays one slice and replenishes after it fills; each fresh slice joins the back of its price queue. TWAP submits equal-sized slices on market time and cancels unfinished orders when its time window ends. A ladder spreads shares downward for buys or upward for sells. Pausing a program cancels its working orders; resuming continues the remainder. Future slices are funded when submitted and may wait for available buying power.
Chart trading: turn on Trade on chart, then click a price to prepare a limit order. Drag an ordinary order line to change its price. Program orders are managed from the program panel. Scroll to zoom, drag to pan, and press Live to follow the market again.
Market participants remain anonymous during trading. Identities, defaults and the finite clearing reserve appear in the debrief. Defaulted short positions transfer with their remaining cash to this reserve; it can also run out of funds, leaving an explicit outstanding liability.
Repeat a seed recreates initial conditions and the background event. Different orders alter participants’ positions and the resulting price path.
Fictional game model. One asset, no options or cross-market hedges yet. The replay’s economic reference is a model estimate, not a future-price guarantee.