# Tuning constants: one header per namespace

Every tunable number of the design (DESIGN_UE.md section 1.3, `DescentTuning.h`) lives in a header of this
folder, **one header per namespace**, named `DescentTune_<Name>.h`, in namespace `Descent::Tune::<Name>`:

```cpp
// Core/Tuning/DescentTune_Carrier.h
#pragma once
#include "CoreMinimal.h"
namespace Descent::Tune::Carrier
{
    constexpr double TopSpeedMps = 2.0;      // U9: keep v2's top speed, reach it in a few seconds
}
```

Rules:

1. **Include the header you need, directly.** There is no umbrella header (`DescentTuning.h` does not exist and
   must not be created), so adding a namespace never edits a file another track also edits.
2. **A new namespace is a new file.** Your track creates `DescentTune_<Name>.h` for its own constants and
   nobody else touches it. Do not add your constants to somebody else's header; if you need their number,
   include their header.
3. Constants are `constexpr` (or `inline constexpr`) with the unit in the name or the comment (`...M`, `...Mps`,
   `...Sec`, `...Deg`). No mutable globals here. User-tunable values are console variables (`descent.<Area>.<Name>`)
   defined in the owning system's `.cpp`, with the default taken from the constant.
4. Header-only, no includes beyond `CoreMinimal.h`, so any file can include them cheaply.

Existing headers (core task): `DescentTune_Sim.h` (sim step clamp, fast-forward defaults),
`DescentTune_Env.h` (dry cabin temperature, water temperature coefficients).