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 skills add MRCalderon3D/everything-game-dev-code --skill core-loop-designgit clone --depth 1 https://github.com/MRCalderon3D/everything-game-dev-codeWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/mrcalderon3d/everything-game-dev-code/core-loop-design)<a href="https://agentmods.dev/skills/mrcalderon3d/everything-game-dev-code/core-loop-design"><img src="https://agentmods.dev/badge/skills/mrcalderon3d/everything-game-dev-code/core-loop-design/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/mrcalderon3d/everything-game-dev-code/core-loop-design"><img src="https://agentmods.dev/badge/skills/mrcalderon3d/everything-game-dev-code/core-loop-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What 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 5.1 | $0.00023 | $0.00417 |
| Opus 5.5 | $0.00009 | $0.00167 |
| Sonnet 5.5 | $0.00005 | $0.00083 |
| Haiku 4.5 | $0.00002 | $0.00042 |
Grade A, and why
core-loop-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 1mo 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.
What it actually says
Core Loop Design
Purpose
Define the primary player activity loop and the support loops that sustain mastery, variety, and progression.
Use When
- a concept needs gameplay structure
- the current loop feels unfocused
- new systems risk diluting the core fantasy
Inputs
- product pillars
- target audience
- competitive references
- session and progression goals
Process
- state what the player repeatedly does and why it is satisfying
- map supporting loops that reinforce the core loop
- identify inputs, feedback, rewards, and failure points
- test whether the loop fits the intended session length and mastery curve
- cut systems that do not serve the loop
Outputs
- core loop definition
- support loop map
- design constraints
- candidate tutorial beats
Quality Bar
- the loop is expressible as a closed cycle of player actions, rewards, and re-entry motivation
- each loop step names the player verb, the feedback, and a duration target
- supporting loops (session, progression, economy) are explicitly connected to the core loop
- the loop is testable in a gray-box build without final art
Common Failure Modes
- loops that depend on content volume instead of repeatable mechanics
- reward steps without a defined re-entry hook back into the loop
- a core loop tuned only on paper, never validated in a playable slice
- conflating the core loop with the meta progression that wraps it
Related Agents
- systems-designer
- gdd-designer
- level-designer
Related Commands
- gdd
- plan
- onboarding
Notes
- Keep this skill aligned with the relevant rules layer and current project documentation.
- If engine-specific constraints materially change the workflow, hand off to the matching engine skill or engine-specific reviewer.
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.
- 1mo ago First seen · 62 lines · 23 tokens per session scan A 0520b2730cde
core-loop-design is a skill published in the GitHub repository MRCalderon3D/everything-game-dev-code (96 stars, last pushed 11d ago), licensed MIT. It adds 23 tokens to every session and 417 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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