# Content Boundary > Content boundary philosophy for FlatRedBall2. Defines what AI produces vs what the human produces (content, feel, placement). Trigger before adding a new level, UI screen, sprite, platformer entity, or any asset the engine loads at runtime — and when designing engine APIs that expose tunable values. - Skill: `vchelaru/content-boundary` (Agent Skill) - Install (CLI): `npx skillmds@latest add vchelaru/content-boundary` - Raw SKILL.md: https://api.skillmd.com/api/skills/vchelaru/content-boundary/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: vchelaru (https://skillmd.com/u/vchelaru) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/vchelaru/content-boundary --- # The AI / Human Content Boundary FlatRedBall2 assumes a **soft split of labor** between AI and human. The split exists because AI has hard limits on a few things, and hiding those limits behind "AI does everything" produces worse games than embracing the split. ## What AI Produces - **Code and structure** — entities, screens, factories, collision wiring, state machines, input handling. - **Placeholders and scaffolding** — valid-but-minimal TMX files, flat Gum screens, default coefficients, shape-based "programmer art" in place of sprites. - **Logic and integration** — loading assets by known path, wiring coefficients from JSON, responding to collision events. ## What the Human Produces - **Raster art** — PNG sprites, backgrounds, UI art. AI cannot create these. - **Level design and placement** — where platforms go, where enemies spawn, pacing, difficulty curve. AI cannot *see* a rendered level or *play* it to judge flow. - **UI composition** — where controls sit on screen, visual hierarchy, typography. AI cannot see the rendered result. - **Feel tuning** — jump height, run speed, friction, drag, attack timing. AI cannot feel gameplay. AI and human can both edit code when needed, but the asymmetry is real: AI writing code is fast and reliable; AI composing art or tuning feel is slow and unreliable. Design around that. ## Engine Design Implication — Externalize What the Human Tunes When designing or reviewing an engine API, ask: *will a human want to tune this without recompiling?* - **Yes** → the API must accept externalized data (JSON, TMX, .gumx, .achx). Example: `PlatformerValues` are consumed from JSON at runtime so designers can iterate in a text editor. - **No** → code-only is fine. This is the lens behind decisions like JSON-driven platformer coefficients, TMX-driven level geometry, and `.gumx`-driven UI layouts. Avoid hardcoding anything a designer would reasonably want to tune by hand. ## Operational Rule — Always Scaffold the Placeholder When a game task adds a new piece of content, AI **must create a placeholder file** rather than hardcoding the content in C#. After scaffolding, tell the user which file to open in which tool. | Adding... | Scaffold | Template source | Human opens in... | |-----------|----------|-----------------|--------------------| | A new level | Minimal TMX with collision layer, one spawn marker (see `tmx` skill) | `.claude/templates/Tiled/base.tmx` | Tiled | | A new UI screen | Gum screen with named controls in a flat list (see `gum-integration` / `gumcli` skills) | — | Gum Tool | | A new platformer entity | `player.platformer.json` with movement coefficients (see `platformer-movement` skill) | `.claude/templates/PlatformerConfig/player.platformer.json` | Text editor (JSON) | | A new top-down entity | `player.topdown.json` with movement coefficients (see `top-down-movement` skill) | `.claude/templates/TopDownConfig/player.topdown.json` | Text editor (JSON) | | A new animated entity | `.achx` referencing a placeholder spritesheet path | `.claude/templates/AnimationChains/` | Aseprite / FRB animation editor | | A new sprite-bearing entity | Code expects `EntityName.png` at a documented size/path | — | Any image editor | Templates live in `.claude/templates/` — copy from there into the project's `Content/` folder, then adjust values. Add the appropriate `` to the `.csproj` for JSON-based content. The scaffold must be *valid and runnable* — the game should build and play immediately, using shape-based stand-ins for missing art. The human then iterates on content without the AI being in the loop. ### The One-of-Each Rule **Scaffold exactly one of each thing the code references — not zero, not many.** The scaffold's job is to prove every code path has a reachable content path. It is a smoke test, not a playable level. - **Zero is a silent failure.** If code calls `GenerateCollisionFromClass("Ladder")` but the TMX has no ladder tiles, the game builds and runs but the feature can't be tested. No error, just absent behavior — the worst kind of bug, because the user sees a working game and assumes the feature is broken. - **Many is AI doing level design.** More than one instance means AI is making placement decisions — pacing, spacing, challenge, layout — which is human work. Do not author a 60×30 "demo level" with platforms and gaps arranged to showcase mechanics; place one tile of each referenced class and stop. - **If you find yourself reaching for a loop, a procedural generator, or an external tool (Python, shell scripts) to produce tile data, stop.** You have crossed from scaffolding into authoring. The scaffold should be small enough to type by hand in under a minute. Concrete examples of "one of each": | Code references | Scaffold must contain | |-----------------|------------------------| | `GenerateCollisionFromClass("SolidCollision")` | The base template's walled arena (already present in `base.tmx` — do not strip it) | | `GenerateCollisionFromClass("Ladder")` | Exactly 1 ladder tile, placed in the open interior | | `GenerateCollisionFromClass("Fence")` | Exactly 1 fence tile, placed in the open interior | | `map.CreateEntities("Coin", coinFactory)` | Exactly 1 coin marker | | `map.CreateEntities("PlayerSpawn", ...)` | Exactly 1 player-spawn marker | The human opens the scaffold in Tiled, sees that every collision/entity type is hooked up correctly, and then designs the real level by copying tiles around. If anything is missing, they notice immediately — because the code references it but there's no tile for it. ## Hot Reload — Required for Every Gameplay Screen The human iterates on content (TMX, JSON, PNGs) while the game is running. Without hot reload they must restart the game after every edit — this breaks the feedback loop that makes content authoring practical. **Every gameplay screen must wire `WatchContentDirectory` in `CustomInitialize`.** The minimum recipe: ```csharp WatchContentDirectory("Content", _ => RestartScreen(RestartMode.HotReload)); ``` If the screen has state worth preserving across restarts (player position, score), also implement `SaveHotReloadState` / `RestoreHotReloadState`. See the `content-hot-reload` and `screens` skills for the full recipe. This is not optional polish — it is a prerequisite for the human to do their half of the work. Always include it. **When in doubt, add it.** This applies equally to test samples, eval samples, collision harnesses, and one-screen reaction tests — anything the human will open in Tiled, Aseprite, or a JSON editor to iterate. The only screens that may skip hot reload are ones with no loaded content at all (pure code-driven demos with no TMX/PNG/JSON/Gum files under `Content/`). ## Visual Semantics Rule (Mechanic Readability) When using placeholder visuals, map gameplay function to a distinct shape + color combo: - If two things behave differently, they should not look like minor variations of each other. - Do not encode critical differences with color shade alone (for example, two similar reds). - Prefer shape differences first (circle vs square vs triangle vs etc), then reinforce with clearly separated colors. Quick checklist: - Different hazard mechanics (damage vs pushback) should not share the same silhouette. - State changes with gameplay impact should have a visible cue. This is a heuristic, not a rigid style guide, but default to it unless the user gives a conflicting art direction. ## Handoff Communication After scaffolding, close the loop with the user explicitly. A good handoff looks like: > I added `Content/Tiled/Level2.tmx` with a collision layer and a player-spawn tile. Open it in Tiled to lay out the level. I also added `Entities/Boss.cs` expecting `Content/Boss.png` (64×64) — drop that PNG in when you have art. Use this compact handoff template when possible: - File: `` - Tool: `` - Action: `` Do not bury this in a summary. The user needs to know exactly which files to open and which tools to use, because that is the half of the work AI can't do. ## Anti-Patterns - **Hardcoding level geometry in C#** instead of a TMX — the human now has to edit code to move a platform. - **Authoring a full level in the scaffold** (platforms, gaps, challenge arrangements) instead of placing one of each referenced tile class. Violates the one-of-each rule above. If you're generating tile CSV with a loop or an external script, you have already failed the rule. - **Hardcoding `PlatformerValues` in C#** (`new PlatformerValues { MaxSpeedX = 150f, ... }`) instead of a `player.platformer.json` — every tuning pass is a recompile. Use `PlatformerConfig.FromJson(...).ApplyTo(behavior)` instead. - **Hardcoding `TopDownValues` in C#** (`new TopDownValues { MaxSpeed = 150f, ... }`) instead of a `player.topdown.json` — same reasoning. Use `TopDownConfig.FromJson(...).ApplyTo(behavior)` instead. - **Generating sprites procedurally "to avoid needing art"** — it is almost always better to use a shape placeholder and have the human drop real art in later. - **Silently skipping the handoff** — finishing a task without telling the user which files they need to touch. ## When the Rule Bends - **One-off prototypes** where the human explicitly says "just hardcode it, I'm throwing this away" — fine, skip the scaffold. - **Values that are truly engine-internal** (collision epsilon, physics integration constants) — these are not "designer tunables"; hardcode them. - **Tiny UI** (a single debug label) — a Gum project file is overkill; inline is fine. Graduate to a project file once there's a second control. If in doubt, scaffold. The cost of an extra file is trivial; the cost of unscaffolded content is the human editing code to tune a jump.