Limit Order Book / matching engine

Two sources, one engine. Synthetic generates a stream of orders (resting quotes on both sides, plus aggressive orders that cross the spread) and matches them live. Real · AAPL replays a recorded slice of NASDAQ TotalView-ITCH, rebuilding Apple's actual book from that session. Both run entirely in WebAssembly and update every frame:

• Ladder resting limit orders by price. Asks (sells) sit above the mid, bids (buys) below; the bar shows size relative to the deepest level. The best bid and best ask meet at the spread.
• Tape executions as they print, newest on top. A trade fires whenever an incoming order crosses the spread and matches resting size at the maker's price.
• Stats live top of book, the count of resting orders, cumulative matches, and how many orders the engine is processing per second. Drag Speed to push it harder.