A "just transition" only works if reskilling programmes can move laid-off fossil-fuel workers into renewable-sector jobs as fast as the old jobs disappear. This simulator models that flow as five linked stocks — fossil-fuel employment, an unemployment queue, an in-training pipeline with a real time delay, a graduated-but-unplaced pool, and renewable employment — and renders each as a filling 3D tank connected by a flowing particle stream. Tune the layoff rate, retraining capacity, training duration, dropout rate and job-growth rate to see exactly where the pipeline bottlenecks: too little retraining capacity strands workers in unemployment, too long a training duration delays graduates, and too little job growth leaves finished trainees waiting for a position that doesn't exist yet.