Conversation Summary (Jan 29, 2026)

Goals and constraints

User wants design suggestions only (no code changes) for refactoring SphereLevel into core architecture.
Keep gameplay logic in projected 2D for now; 4D is future-facing and should not drive current implementation details.
Prefer an approach that does not introduce "code smell" for 2D levels.

Projected 2D collisions are acceptable; the game remains 2D at its core with spatial presentation layers.
Arrow effects already spawn after connection via EffectsFactory and should continue to follow projected line points.
Obstacles should remain 2D overlays under projected-2D rules (same as current Sphere behavior).
Clock in 3D should remain a 2D overlay to match current Sphere behavior and maintain collision semantics.
Avoid a mandatory "space mode" for 2D. Use an optional spatializer only when Dimension > 2.
Spatializer can act as a preset that also owns core behaviors, with optional internal modifiers. (optional)

Option A (Optional Spatializer) is preferred:
- Keep existing BaseLevel rule classes (Standard/Clock/DarkMode/etc).
- Add an optional spatializer only for Dimension > 2.
- Spatializer owns projection, visibility/backface logic, overlays (equator), and rotation input.
- 2D levels remain unchanged and bypass the spatializer entirely.
Option B (Level Modifiers) was discussed as a more composable alternative:
- Keep rules unchanged.
- Add a list of LevelModifiers in data (e.g., SphereProjection, EquatorOverlay, RotationInput).
- Only levels that need 3D/4D attach modifiers.
- Requires ordering/dependency management between modifiers.