What is fog-of-war-js-ts?

A guide to visibility systems in JavaScript and TypeScript games. Fog of war hides unexplored areas, while field of view and line of sight determine what players or game units can currently see.

It is for building or improving visibility on grid or continuous maps in roguelikes, real-time strategy games, top-down games, and other strategy maps.

It helps avoid slow recalculation, visual errors such as light leaks, and excessive memory use as maps or the number of units grow.

fog-of-war-js-ts — Skill for Claude Code and Codex by pproenca

Install

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.

Any agent

npx skills add pproenca/dot-skills --skill fog-of-war-js-ts

Clone the repo

git clone --depth 1 https://github.com/pproenca/dot-skills

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/pproenca/dot-skills/fog-of-war-js-ts/github.svg)](https://agentmods.dev/skills/pproenca/dot-skills/fog-of-war-js-ts)

Your own site

<a href="https://agentmods.dev/skills/pproenca/dot-skills/fog-of-war-js-ts"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/fog-of-war-js-ts/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/pproenca/dot-skills/fog-of-war-js-ts"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/fog-of-war-js-ts.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 183 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,159 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

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	$0.00183	$0.02159
Opus 5	$0.00092	$0.01079
Sonnet 5	$0.00037	$0.00432
Haiku 4.5	$0.00018	$0.00216

Measured 8d ago against content hash 91d8c25c4614, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

fog-of-war-js-ts 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 8d 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.

skills/.experimental/fog-of-war-js-ts/SKILL.md · 116 lines

How it starts

The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.

dot-skills Fog of War (JavaScript/TypeScript) Best Practices

Performance and correctness guide for fog of war and field-of-view systems in JS/TS games, distilled from the canonical FOV literature (Björn Bergström, Albert Ford, Adam Milazzo), Red Blob Games, rot.js, and the MDN/WebGL rendering APIs. Contains 44 rules across 8 categories, ordered by impact, to guide writing, reviewing, and refactoring visibility code.

When to Apply

Reference these guidelines when:

Implementing field of view, line of sight, or tile visibility for a grid or continuous map
Building or refactoring a fog-of-war display (unexplored / explored / visible layers)
Diagnosing slow fog (recompute every frame), visual artifacts (flicker, light leaks), or memory blowups on large maps
Scaling visibility to many units (RTS) or to large/streaming worlds
Choosing how to store and render the visibility/explored state

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	FOV / Visibility Algorithm	CRITICAL	`fov-`
2	Update Scheduling & Incremental Recompute	CRITICAL	`update-`
3	State Representation & Data Structures	HIGH	`state-`
4	Rendering the Fog Layer	HIGH	`render-`
5	Memory & Allocation	MEDIUM-HIGH	`mem-`
6	Multi-Viewer & Map Scaling	MEDIUM	`scale-`
7	Geometry & Hot-Loop Math	MEDIUM	`geo-`
8	Correctness & Visual Artifacts	LOW-MEDIUM	`correct-`

Quick Reference

1. FOV / Visibility Algorithm (CRITICAL)

fov-recursive-shadowcasting - Use recursive shadowcasting, not ray-per-cell FOV
fov-symmetric-shadowcasting - Prefer symmetric shadowcasting for consistent visibility
fov-octant-transforms - Transform octants with a lookup table, not eight loops
fov-radius-bounded-scan - Bound the scan to the sight radius and map edges
fov-single-ray-los - Use a single line-of-sight ray for point-to-point checks
fov-dda-continuous - Traverse continuous space with a DDA grid walk
fov-visibility-polygon - Compute a visibility polygon for smooth 2D fog

Read the full file on GitHub · 116 lines

Files

What ships with it

48 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

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.

8d ago First seen · 116 lines · 183 tokens per session scan A 91d8c25c4614

Subscribe to this mod's changes

fog-of-war-js-ts is a skill published in the GitHub repository pproenca/dot-skills (207 stars, last pushed 27d ago), licensed MIT. It adds 183 tokens to every session and 2,159 once invoked, about $0.0009 per session on Opus 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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fog-of-war-js-ts