islaApocalypse-v2/Core/README.md
beezm 9107b0822b Phase 0: clean project skeleton for the v2 rewrite
Stands up the CODE_REPO the rewrite is written into (D-049, D-058). Godot 4.7.2 /
.NET 8 / Godot.NET.Sdk 4.7.2. Nothing is generated, meshed, or ported — this is the
shell and the two data contracts.

Four layers, each with its boundary stated in a directory README:
  Core/    math + data only, and engine-free — depends on nothing above it
  Server/  authoritative logic                (empty this phase)
  Client/  rendering                          (empty this phase)
  Tools/   the offline generator — may NOT reference Client   (Phase 1 fills it)

Contracts (compiling stubs, no algorithms):
  - Column model (D-053): a 2D grid of columns, each a stack of (material, thickness)
    runs, any material at any depth. Air is the TOP RUN — there is no air-vs-solid
    height branch, and no surface-height accessor exists to reintroduce one. Water is
    not a band; it stays an overlay.
  - Material schemas (D-054): terrain and building as two append-only registries,
    bridged by a recipe seam that is deliberately EMPTY. Identity is a registry key,
    never a serialized ordinal. Mesh style is per-ORIGIN and is not a material field.

Rails, so Phase 1 inherits them rather than rediscovering them:
  - GenerationScale: MapSize is a parameter, everything derives from it, nothing uses
    a raw pixel number. Tightening over the reference — decorrelation offsets are
    declared in map widths, not pixels (chat1/00 §4.2).
  - ToolingPaths: config/blueprint/output paths all env-overridable, resolved in one
    place, so a batch cannot touch the developer's live files.
  - FileSafety: the permanent no-deletion rules as throws rather than sentences.

user:// isolation: project name and use_custom_user_dir both pin the runtime dir to
~/.local/share/islaApocalypse-v2/, away from the old prototype's preserved seeds and
batches. Tools/Scenes/UserDirProbe.tscn confirms it rather than assuming it.
2026-08-19 20:21:12 -04:00

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# Core — math and data only
**Holds:** the column model, the material schemas, the scaling discipline, tooling path
resolution and the file-safety rails. Constants and contracts.
**Boundary: Core depends on nothing above it.** Not on `Server/`, not on `Client/`, not on
`Tools/`. The dependency arrow points one way into this folder and never out of it.
> ### ⚠ Additional boundary, tighter than the layer rule: **Core is engine-free.**
>
> No `using Godot;` anywhere in this folder. Core is plain C# — no `Node`, no `GD.Print`, no
> `ProjectSettings`, no engine types in any signature.
>
> **Two reasons, both load-bearing.** (1) D-049 commits to *"C# for fast iteration, with C++-ready
> seams… port path-by-path when settled and hot"* — the hot paths that get ported first are exactly
> the ones in here, and a type that names `Godot.Vector2` cannot cross that seam. (2) It keeps the
> column model testable and reviewable without standing up an engine.
>
> Where Core genuinely needs something the engine knows — the resolved `user://` directory — the
> engine layer **hands it in** (`ToolingPaths.Configure`), rather than Core reaching for it.
> If you find yourself wanting an engine type here, the type belongs one layer up.
## What is in here
| File | What it is |
|---|---|
| `Scripts/Column.cs` | ★★ **The load-bearing contract** (D-053). A column as run-length bands; `MaterialRun`; `RunOrigin`. Read its header before touching anything that stores world data. |
| `Scripts/ColumnGrid.cs` | The 2D grid of columns. Shape only — chunking and streaming are later phases. |
| `Scripts/MaterialKey.cs` | Material **identity** — a registry key, never an ordinal. |
| `Scripts/TerrainMaterial.cs` | A row in the terrain schema (D-054). |
| `Scripts/BuildingMaterial.cs` | A row in the building schema (D-054). |
| `Scripts/MaterialRegistry.cs` | Both registries, append-only, seed rows only. |
| `Scripts/RecipeRegistry.cs` | The transformation seam — **deliberately empty**. |
| `Scripts/GenerationScale.cs` | ⭐ The scaling discipline. `MapSize`, `ScaleFactor`, normalized offsets. |
| `Scripts/ToolingPaths.cs` | Every tooling path, env-overridable, resolved in one place. |
| `Scripts/FileSafety.cs` | The permanent file-safety rules, as throws rather than sentences. |
## The three rules this layer exists to make unbreakable
1. **Air is the top run.** There is no "air vs solid" height branch, anywhere, ever.
`Scripts/Column.cs`.
2. **Properties come from the registry, never from storage.** A run stores an identity.
`Scripts/MaterialRegistry.cs`.
3. **Nothing uses a raw pixel number.** Every distance is a fraction of `MapSize`.
`Scripts/GenerationScale.cs`.
## Not here, and not by accident
- **No water.** Water is an overlay over the columns (levels-not-cells), never a band.
- **No biomes.** Biomes are a later *classification* of finished shape, not an input to it (D-049).
- **No algorithms.** Phase 0 is shape. Stratigraphy, feature passes, meshing and run-splitting on
dig are later phases.
`Design - Data - Column Model.md`, `Design - Data - Material Schema.md`,
`Design - Tooling - Scaling Discipline.md`