Inputs: underlying ticker (auto-fills current price), legs (call/put, long/short, strike, expiration), and entry premium for each. Output: P&L curve from -50% to +50% of current price, with breakevens, max gain, max loss, and current P&L marked. Toggle between 'at expiration' view and 'today' view (which uses the option pricing model to show current P&L given days remaining and current IV).
Practical uses: comparing two candidate structures side-by-side before entry, stress-testing a position across price scenarios, and explaining a multi-leg structure visually to a less-experienced trader. The diagram is the single most useful pedagogical tool for understanding how multi-leg options strategies actually work.