blECSd Codex Skill

Use this skill to build, review, or refactor blECSd applications and libraries.

Follow Core Principles

• Treat blECSd as a library, not a framework.
• Use functional style only: pure functions, plain data, no classes.
• Use ECS patterns: entities as IDs, components as SoA data, systems as pure transforms.
• Keep input responsive: INPUT phase runs first and drains events.

Choose an API

• Use Game API for games and real-time apps.
• Use ECS API for full control and performance tuning.

Apply the Recommended Workflow

1. Pick the API surface.

• Import from blecsd for typical apps.
• Import from blecsd/terminal for low-level terminal control.
• Import from blecsd/components and blecsd/systems for custom pipelines.

2. Create the world and screen.

• Call createWorld and createScreenEntity for ECS API.
• Call createGame for Game API.

3. Build UI with the right abstraction.

• Use widgets for rapid development.
• Use entity factories for composable primitives.
• Use components directly for full control.

4. Handle input first.

• Keep input logic in INPUT/EARLY_UPDATE.
• Avoid input processing in RENDER.

5. Render after layout.

• Run LAYOUT before RENDER.
• Keep RENDER read-only.

6. Optimize only when measured.

• Use frame budget tooling and benchmarks.
• Apply virtualization and dirty tracking for large UIs.

Keep Best Practices in Mind

• Cache queries outside hot loops.
• Keep hierarchies shallow.
• Use VirtualizedList for lists > 1000 items.
• Mark entities dirty only when state changes.
• Use visibility culling for large scenes.
• Batch updates and render once per frame.
• Store large data outside ECS; keep ECS for UI state.
• Access component arrays directly in tight loops.

Read Deep Dives as Needed

Indexes and summaries for full coverage:

• references/DOCS_INDEX.md
• references/ROOT_DOCS.md
• references/ROOT_DOCS_SUMMARY.md
• references/GETTING_STARTED_INDEX.md
• references/GETTING_STARTED_SUMMARY.md
• references/GUIDES_INDEX.md
• references/GUIDES_SUMMARY.md
• references/TUTORIALS_INDEX.md
• references/TUTORIALS_SUMMARY.md
• references/EXAMPLES_INDEX.md
• references/EXAMPLES_SUMMARY.md
• references/ARCHITECTURE_INDEX.md
• references/ARCHITECTURE_SUMMARY.md
• references/PERFORMANCE_INDEX.md
• references/PERFORMANCE_SUMMARY.md
• references/CONTRIBUTING_INDEX.md
• references/CONTRIBUTING_SUMMARY.md
• references/EXPLORATION_INDEX.md
• references/EXPLORATION_SUMMARY.md

API indexes:

• references/API_INDEX.md
• references/API_CORE.md
• references/API_COMPONENTS.md
• references/API_WIDGETS.md
• references/API_SYSTEMS.md
• references/API_TERMINAL.md
• references/API_UTILS.md
• references/API_3D.md
• references/API_DEBUG.md
• references/API_INPUT.md
• references/API_TEXT.md

Focused deep dives:

• references/MODULES.md
• references/BEST_PRACTICES.md
• references/PERFORMANCE.md
• references/SYSTEMS.md
• references/LAYOUT.md
• references/WIDGETS.md
• references/COMPONENTS.md
• references/TERMINAL.md
• references/TERMINAL_PROTOCOLS.md
• references/UTILS.md
• references/THREE_D.md
• references/ERRORS.md
• references/SCHEMAS.md
• references/TESTING.md
• references/GAME_API.md
• references/ECS_API.md
• references/ARCHITECTURE.md

Enforce Guardrails

• Never introduce classes or new (except built-in collections like Map, Set, Error).
• Keep nesting shallow with guard clauses.
• Use Zod validation at system boundaries.
• Prefer ECS systems for behavior; keep state in components.

Use a Quick ECS Example

import {
  createWorld,
  createScreenEntity,
  createBoxEntity,
  createGameLoop,
  LoopPhase,
  inputSystem,
  layoutSystem,
  renderSystem,
} from 'blecsd';

const world = createWorld();
createScreenEntity(world, { width: 80, height: 24 });
createBoxEntity(world, { x: 2, y: 1, width: 30, height: 10, title: 'Hello' });

const loop = createGameLoop(world, { targetFPS: 60 });
loop.registerSystem(LoopPhase.INPUT, inputSystem);
loop.registerSystem(LoopPhase.LAYOUT, layoutSystem);
loop.registerSystem(LoopPhase.RENDER, renderSystem);
loop.start();