Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/diillson/chatcli/2d-gamesnpx skills add diillson/chatcli --skill 2d-gamesgit clone --depth 1 https://github.com/diillson/chatcliWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00020 | $0.00554 |
| Opus 5 | $0.00010 | $0.00277 |
| Sonnet 5 | $0.00004 | $0.00111 |
| Haiku 4.5 | $0.00002 | $0.00055 |
Grade A, and why
2d-games scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
100% identical to 2d-games — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.
2D Game Development
Principles for 2D game systems.
1. Sprite Systems
Sprite Organization
| Component | Purpose |
|---|---|
| Atlas | Combine textures, reduce draw calls |
| Animation | Frame sequences |
| Pivot | Rotation/scale origin |
| Layering | Z-order control |
Animation Principles
- Frame rate: 8-24 FPS typical
- Squash and stretch for impact
- Anticipation before action
- Follow-through after action
2. Tilemap Design
Tile Considerations
| Factor | Recommendation |
|---|---|
| Size | 16x16, 32x32, 64x64 |
| Auto-tiling | Use for terrain |
| Collision | Simplified shapes |
Layers
| Layer | Content |
|---|---|
| Background | Non-interactive scenery |
| Terrain | Walkable ground |
| Props | Interactive objects |
| Foreground | Parallax overlay |
3. 2D Physics
Collision Shapes
| Shape | Use Case |
|---|---|
| Box | Rectangular objects |
| Circle | Balls, rounded |
| Capsule | Characters |
| Polygon | Complex shapes |
Physics Considerations
- Pixel-perfect vs physics-based
- Fixed timestep for consistency
- Layers for filtering
4. Camera Systems
Camera Types
| Type | Use |
|---|---|
| Follow | Track player |
| Look-ahead | Anticipate movement |
| Multi-target | Two-player |
| Room-based | Metroidvania |
Screen Shake
- Short duration (50-200ms)
- Diminishing intensity
- Use sparingly
5. Genre Patterns
Platformer
- Coyote time (leniency after edge)
- Jump buffering
- Variable jump height
Top-down
- 8-directional or free movement
- Aim-based or auto-aim
- Consider rotation or not
6. Anti-Patterns
| ❌ Don't | ✅ Do |
|---|---|
| Separate textures | Use atlases |
| Complex collision shapes | Simplified collision |
| Jittery camera | Smooth following |
| Pixel-perfect on physics | Choose one approach |
Remember: 2D is about clarity. Every pixel should communicate.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 120 lines · 20 tokens per session scan A f31d95e041d0
2d-games is a skill published in the GitHub repository diillson/chatcli (89 stars, last pushed 4d ago), licensed Apache-2.0. It adds 20 tokens to every session and 554 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to 2d-games, differing in 0 lines, and is treated as a copy.
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