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/felipeslo/opencode-kit/game-designnpx skills add felipeslo/opencode-kit --skill game-designgit clone --depth 1 https://github.com/felipeslo/opencode-kitWhat 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 | $0.00018 | $0.00629 |
| Opus 5 | $0.00009 | $0.00315 |
| Sonnet 5 | $0.00004 | $0.00126 |
| Haiku 4.5 | $0.00002 | $0.00063 |
Grade A, and why
game-design 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 yesterday.
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
98% identical to game-design — 1 line 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 — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Game Design Principles
Design thinking for engaging games.
1. Core Loop Design
The 30-Second Test
Every game needs a fun 30-second loop:
1. ACTION → Player does something
2. FEEDBACK → Game responds
3. REWARD → Player feels good
4. REPEAT
Loop Examples
| Genre | Core Loop |
|---|---|
| Platformer | Run → Jump → Land → Collect |
| Shooter | Aim → Shoot → Kill → Loot |
| Puzzle | Observe → Think → Solve → Advance |
| RPG | Explore → Fight → Level → Gear |
2. Game Design Document (GDD)
Essential Sections
| Section | Content |
|---|---|
| Pitch | One-sentence description |
| Core Loop | 30-second gameplay |
| Mechanics | How systems work |
| Progression | How player advances |
| Art Style | Visual direction |
| Audio | Sound direction |
Principles
- Keep it living (update regularly)
- Visuals help communicate
- Less is more (start small)
3. Player Psychology
Motivation Types
| Type | Driven By |
|---|---|
| Achiever | Goals, completion |
| Explorer | Discovery, secrets |
| Socializer | Interaction, community |
| Killer | Competition, dominance |
Reward Schedules
| Schedule | Effect | Use |
|---|---|---|
| Fixed | Predictable | Milestone rewards |
| Variable | Addictive | Loot drops |
| Ratio | Effort-based | Grind games |
4. Difficulty Balancing
Flow State
Too Hard → Frustration → Quit
Too Easy → Boredom → Quit
Just Right → Flow → Engagement
Balancing Strategies
| Strategy | How |
|---|---|
| Dynamic | Adjust to player skill |
| Selection | Let player choose |
| Accessibility | Options for all |
5. Progression Design
Progression Types
| Type | Example |
|---|---|
| Skill | Player gets better |
| Power | Character gets stronger |
| Content | New areas unlock |
| Story | Narrative advances |
Pacing Principles
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.
- yesterday First seen · 129 lines · 18 tokens per session scan A 369ecc52b546
game-design is a skill published in the GitHub repository felipeslo/opencode-kit (2 stars, last pushed 5mo ago), licensed MIT. It adds 18 tokens to every session and 629 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 98% identical to game-design, differing in 1 line, and is treated as a copy.
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