A float can hold any number, which is exactly the problem. Primitive obsession is why the same validation keeps reappearing, and value objects are the fix.

The Single Responsibility Principle is the most misread rule in SOLID: it was never about doing one thing, but about having one clear reason to change.

A pure function returns the same output for the same input and touches nothing else. That single property is what makes code predictable and trivial to test.

Deeply nested if/else blocks are hard to read and easy to break. Guard clauses flatten your logic with early returns so the happy path stays obvious.