QFA / An interactive introduction

Make a Market.

You quote a price to buy and a price to sell. Keep both sides attractive without taking on too much inventory.

60-second session / Synthetic marketReady to quote

Try this: Start a round. Keep your buying price below your selling price. If inventory grows, shift both prices down to encourage sales.

Time remaining60s

Mid-price100.00

Inventory0

Marked P&L0.00

Price starts at 100.00

Bid · You buy99.80

Ask · You sell100.20

Spread · gap between prices 0.40Narrower spreads can attract more fills.Shift both prices 0.00Shift down to encourage sales; up to encourage purchases.

Choose a spread, then start. Inventory is limited to ±10 units.

Order flow

Your trade tape will appear here.

What you’re balancing

Spread

The gap between your buy and sell prices. More profit per matched pair can mean fewer trades.

Inventory

Buying builds inventory; selling reduces it. A price move affects the value of everything you hold.

Risk

Your score subtracts an inventory-risk charge from marked P&L. There’s no guaranteed winning quote.

How the simulation works

Each second, a newly seeded synthetic price moves by up to 0.30. Two simulated customers compare your quotes with their reservation prices. Each fill is one unit, with a 0.01 fee. Marked P&L = cash + inventory × mid-price. Score = final marked P&L − 0.02 × the average squared inventory. A round without trades scores zero; wider spreads can leave you with fewer opportunities. A hidden tab pauses the round. Quotes are not a model of an actual exchange; no real money or market data is involved.