Showoff Saturday] I got tired of heavy fitness apps, so I built a lightweight Vanilla JS PWA with visual muscle fatigue tracking.

Hey everyone,

I wanted a tracker that didn't feel bloated, so I built this entirely in Vanilla JS and Firebase. No heavy frameworks, just raw performance so it loads instantly in the gym.

The hardest part was building the "Biological Fatigue Map". I custom-designed SVG muscle maps for exercises (pull-ups, squats, deadlifts, etc.). The app dynamically colors the SVGs (green/yellow/red) based on the volume logged in the last 72 hours to visualize recovery.

I also implemented an Anonymous Guest Login so anyone can test the UI mechanics without creating an account.

You can try the live PWA here: https://gymtracker-af175.web.app

I'd love some feedback on the codebase approach (Vanilla JS vs moving to React/Vue later) or the UI flow!