Stages of Change: Health Behavior Simulator (2D)

This is the 2D Markov-chain counterpart to the 3D population simulator: the same Transtheoretical Model of behavior change, rendered as an explicit state-machine diagram plus a live chart instead of an orbiting 3D cohort. In Individual mode you watch one simulated person move week by week through Precontemplation, Contemplation, Preparation, Action and Maintenance, with each arrow on the diagram labeled with the exact probability of that transition happening this week given their current self-efficacy. Switch to Population (Monte Carlo) mode to run an entire cohort in parallel and watch the real stage-distribution-over-time curve emerge from nothing but the same per-person transition probabilities — turn up intervention strength to accelerate forward progress, or turn up relapse risk to watch low-self-efficacy people slip back from Action or Maintenance into Contemplation, exactly as the model predicts.