This is a complete, single-file "Guitar Neck Relief & Truss Rod Bow Calculator." It uses a clean, premium aesthetic with glassmorphism, responsive design, and real-time calculation logic, fully self-contained without external storage or dependencies beyond CDNs. ```html Free Guitar Neck Relief & Truss Rod Bow Calculator

Neck Relief Calculator

Enter measurement to assess truss rod status.

Back-bow Optimal Excess
Enter a measurement
Please provide a reading from your feeler gauges.