orderbook — live matching engine (WebAssembly)

Click or focus a ladder level and press enter to rest an order (bid side buys, ask side sells) · your fills push the price (market impact) · fire a news shock or turn up turbulence · space pauses

strategy	order	avg px	shortfall	fill	adv move	time

Work a parent order through the live book. Shortfall is implementation shortfall vs the mid at arrival, in bps (positive = a cost) — unfilled shares are marked at the end mid, so a passive order that misses its fill pays for the move away instead of showing a free pass. adv move is how far the mid moved against your side over the run (your impact plus market drift — one run is mostly noise). Run the same order a few times to compare strategies.

scenario

Market makerquotes both sides, earns the spread, fears inventory

P&L$0.00

inventory0

spread — · adverse — · quotes —/—

½-spread ¢ size inv cap

Momentumbuys strength, sells weakness — rides trends, whipsaws in chop

P&L$0.00

position0

signal

Mean reversionfades moves back to the mean — wins ranges, bleeds in trends

P&L$0.00

position0

signal

Cumulative P&L of each running bot. Pick a scenario and watch who wins: momentum in trends, mean reversion in choppy markets, the maker on spread until adverse selection bites.

Order book depth and recent trades