Startup growth engine (R and B loops)
A system-dynamics model of a viral product whose growth is capped by scaling strain. The engine enumerates every feedback loop and classifies each reinforcing (R) or balancing (B) by Sterman's even/odd rule.
For the systems-thinking strategist
What this shows
The two-sided story of every viral product. One reinforcing loop drives growth: more active users produce more word of mouth, which drives signups, which adds users — an amplifying cycle. A second, balancing loop pushes back: more users raise server load, which degrades app performance, which (after a delay) loses users. The delay markers put the system-dynamics hash mark on the slow legs, where the lag between cause and effect is what makes the system overshoot.
The engine finds and labels the loops for you, which a drawing tool cannot. It enumerates every elementary cycle in the signed graph with Johnson's algorithm, then applies Sterman's rule — count the negative links, even means reinforcing (R), odd means balancing (B) — and numbers them R1, B1… The growth cycle comes back R (zero negatives), the load cycle B (one negative). The named loop declarations attach the human phrasing — "Viral flywheel", "Scaling strain" — onto the loops the engine detects.