How it works
Every workout charges the forge. Keep showing up and it climbs toward supernova.
Charge comes from how long a session runs and how hard it pushes. Duration and effort together produce a calorie burn, and each heart-rate zone weighs those calories differently — an easy hour charges the forge less than a hard one.
From there it fades. Miss a few days and the fire cools; stay away long enough and it goes cold. One hard session does not fill it — the forge builds across a stretch of training, and slipping the rhythm drops you back down.
Cardio, tennis, lifting all count. Harder mixed work holds the fire better than an easy lift alone.
Nothing here is estimated. Every number comes from a real session, logged with its calories and the time spent in each zone.