I need a straightforward financial calculation focused on investments. The task is to work out projected returns, taking into account principal, time horizon, and an annual rate I will supply. There is no requirement for complex portfolio modelling—just a clean, accurate computation that I can reuse or tweak later. You are free to deliver the solution as an Excel sheet, a lightweight Python script, or even a clear-ly laid-out Google Sheet, so long as the formulas are visible and editable. Please show each step (principal growth, compound interest applied, and final value) so I can follow the logic and adjust the inputs myself in the future. Accuracy is more important than fancy formatting, but a tidy presentation will be appreciated.