Nirai

Most system dynamics tools show results as line charts — you read the numbers. Nirai animates the same stock-and-flow model as real water flowing through tanks and pipes, so feedback loops and bottlenecks are something you watch, not decode. Export the whole simulation as MP4 for slides, decks, or explainers — no other SD tool does this. Runs fully in-browser: Rust/WASM engine, RK4 solver, formula engine with lookups + randoms. AI edits your model on-canvas using your own API key.