simcraft

In the author's own words, from each skill's SKILL.md.

• api-design-review

  Review the design of an API surface, meaning an HTTP API (OpenAPI spec or route code), an SDK's public classes and functions, or a CLI. Checks naming and consistency, resource modelling, error design (stable codes, RFC 9457 problem details, request ids), versioning and breaking changes, pagination, filtering, idempotency and retries, rate limits, timeouts, long-running operations, webhooks, auth,…

  skills/coding/api-design-review/SKILL.md on GitHub (opens in a new tab)

• benchmark-honestly

  Build benchmarks that survive scrutiny and catch the classic lies (dead code elimination, lazy results, constant folding, warm caches, coordinated omission, averages hiding GC pauses, unequal work, noisy machines). Defines the question first, controls and discloses the environment, uses warmups, interleaved repeats, medians, bootstrap confidence intervals and Mann-Whitney tests, and ends with a o…

  skills/coding/benchmark-honestly/SKILL.md on GitHub (opens in a new tab)

• bisect-anything

  Find the exact commit (or dependency version, config value, or input) that caused a regression by turning it into an automatic pass/fail check and running git bisect run in a separate worktree, then shrink the bad commit to the hunk that matters and explain it. Handles failing tests, changed output, slowdowns, crashes, visual changes, server behaviour, flaky checks, unbuildable commits and merge-…

  skills/coding/bisect-anything/SKILL.md on GitHub (opens in a new tab)

• codebase-map

  Understand an unfamiliar codebase fast, the way senior engineers do. Reads the orientation signals (README, manifests, CI, Dockerfiles, routes, migrations), mines git history for hotspots, hidden coupling and ownership, builds the import graph to find layers, cycles, load-bearing and dead code, then traces one real request or command end to end by actually running it. Writes MAP.md with a one-par…

  skills/coding/codebase-map/SKILL.md on GitHub (opens in a new tab)

• dx-audit

  Audit the developer experience of a developer tool (SDK, API, CLI, framework) by trying it exactly like a brand-new developer, from the official docs only, in a fresh empty environment. Logs every step with timestamps and friction tags, measures time to first success, steps, page switches, errors and lines of code, finds where people would give up, grades three error messages, and writes a fair t…

  skills/coding/dx-audit/SKILL.md on GitHub (opens in a new tab)

• flaky-test-killer

  Find why a test is flaky and fix the root cause, never by adding retries, sleeps or bigger timeouts. Measures the flake rate with a confidence interval, runs the test under stressors (random order, timezone, fake clock at month end or DST, CPU load, fresh temp dir, low file limits), bisects for the test that pollutes it, and proves the fix with before and after numbers. Use when the user says "fl…

  skills/coding/flaky-test-killer/SKILL.md on GitHub (opens in a new tab)

• security-threat-model

  Threat-model the user's own app from its real code. Draws the data flow (actors, trust boundaries, data stores, external services) as a Mermaid diagram, finds threats per element with STRIDE, ranks them by likelihood times impact, then proves each top risk with a local failing test, fixes it, and keeps the test as a regression test. Covers auth, IDOR and tenant isolation, injection, SSRF, secrets…

  skills/coding/security-threat-model/SKILL.md on GitHub (opens in a new tab)

• brand-kit

  Learn a company's brand design from its live website (colours, fonts with the real font files, logo, button and card shapes, texture, image style) and save it as a reusable kit that vox-explainer and image-gen apply automatically. Use FIRST, before any brand or sponsored video, sticker, graphic or asset for a company (e.g. "a video for Devin", "ChatGPT-style stickers", "match their brand"), or wh…

  skills/design/brand-kit/SKILL.md on GitHub (opens in a new tab)

• image-gen

  Generate images with the user's own API keys (Google Gemini "Nano Banana" or OpenAI gpt-image). Use when asked to generate, create or make an image, illustration, icon, cut-out, sticker, thumbnail, texture, mockup or visual asset, to edit an image, or to make several images that stay consistent (same character or object). Also used by the vox-explainer skill for collage cut-outs.

  skills/design/image-gen/SKILL.md on GitHub (opens in a new tab)

• from-scratch

  Learn how something really works by building the smallest working version of it from scratch, Karpathy style, one small step at a time, with the user predicting what each step will do before running it. Works for ML and AI ideas (attention, tokenizers, backprop, RAG, agents), systems (a database, an HTTP server, git, a shell) and anything else that can be coded. Use when the user says "teach me h…

  skills/learning/from-scratch/SKILL.md on GitHub (opens in a new tab)

• paper-to-runnable

  Turn a research paper (arXiv id, arXiv URL or local PDF) into the smallest honest working implementation of its core idea, checked with a sanity ladder and a toy reproduction of the paper's main result, plus plots or an animation of what happens inside and a short explainer. Use when the user says "implement this paper", "reproduce this paper", "explain this paper by building it", "code up this a…

  skills/learning/paper-to-runnable/SKILL.md on GitHub (opens in a new tab)

• system-design-from-scratch

  Design a backend or distributed system by building a tiny but real working version of it, proving its properties with invariant tests, a load test (throughput and p50/p95/p99 latency) and fault injection (crashed nodes, dropped or delayed messages, partitions, clock skew, full disks), then writing a design doc with the numbers, alternatives, where it breaks, how Redis, Kafka, Cassandra or etcd do…

  skills/learning/system-design-from-scratch/SKILL.md on GitHub (opens in a new tab)

• teach-back

  Find out what the user actually understands about a topic by having them explain it back (the Feynman technique), then probe the gaps one question at a time and end with a one-page cheat sheet and spaced review questions. Works for anything they are studying or have just read, watched or built: a paper, a course, a codebase, an interview topic, a concept. Use when the user says "quiz me", "test m…

  skills/learning/teach-back/SKILL.md on GitHub (opens in a new tab)

• next-step

  Turn a big, messy goal or a brain dump into one clear next action at a time, for people who freeze in front of long to-do lists (ADHD-friendly). Asks one question at a time, keeps a small plan file, and only ever shows the single next step plus how long it takes. Use when the user says "I don't know where to start", "help me plan", "I'm overwhelmed", "what should I do next", "break this down", du…

  skills/planning/next-step/SKILL.md on GitHub (opens in a new tab)

• skill-router

  Decide which installed skill, or which chain of two or three skills, fits a task before starting it, and run them in the right order with each one's output feeding the next. Works with any set of skills, because it reads every installed skill's description at run time. Use when a task is big or vague, could fit several skills, or needs more than one ("which skill should I use", "what's the best w…

  skills/planning/skill-router/SKILL.md on GitHub (opens in a new tab)

• video-script

  Write a short talking-head, explainer or product demo video script (30 seconds to 3 minutes) that sounds like the creator, not like AI. Starts from their own voice-note ramble, builds one question, one story, one lesson, puts the stakes in the first line, sizes it to the target length, and lists every fact to check with sources. Use when asked to write, draft, plan or fix a video script, a hook,…

  skills/planning/video-script/SKILL.md on GitHub (opens in a new tab)

• clean-audio

  Clean up voice audio in a video: rumble, electrical hum, background noise and hiss, muddy or harsh tone, sharp S sounds, uneven volume, and loudness for YouTube/Instagram/TikTok. Measures the audio first, picks the strongest cleanup that doesn't make the words less clear, and keeps lip sync exact. Use when the user says "clean up the audio", "fix the sound", "remove background noise", "remove hum…

  skills/video/clean-audio/SKILL.md on GitHub (opens in a new tab)

• code-loop

  Make a seamless, perfectly looping generative video in code, from a three.js scene or a raw GLSL fragment shader, rendered frame-perfect with jittered anti-aliasing and motion blur, then checked for a visible seam, freezing and blinking. Use when asked for a "seamless loop", a "perfect loop", "generative art video", a "shader loop", "three.js animation to video", to "render a looping animation",…

  skills/video/code-loop/SKILL.md on GitHub (opens in a new tab)

• perspective-illusion

  Make a looping illustrated 3D video in the Japanese perspective-illusion style (e.g. @garments__) of any place, such as a street, crossing, station, shop aisle, room, park or rooftop. A clean line-art scene squashed flat by a telephoto lens opens into deep perspective with dolly zooms, swings round to corner views that first read flat and then turn 3D, and objects quietly swap depth while the vie…

  skills/video/perspective-illusion/SKILL.md on GitHub (opens in a new tab)

• repo-timelapse

  Turn a git repo's history into a video of the project growing. Files appear as a living treemap coloured by language that grows with the code, glows when touched and fades on delete, with a date, a lines-of-code counter, commit messages typing in as captions and an activity sparkline. 16:9 or 9:16, dark or light. Use when the user says "timelapse of my repo", "visualise git history", "build in pu…

  skills/video/repo-timelapse/SKILL.md on GitHub (opens in a new tab)

• reverse-engineer-video

  Break down a reference or viral video clip so it can be remade. Finds every cut and dissolve, times each shot, measures pacing, works out the camera move in each shot (static, pan, tilt, zoom or push in, roll, handheld shake, with speed), finds beats and loudness jumps and checks whether the cuts land on them, and reads on-screen text and speech when the tools are installed. Makes a contact sheet…

  skills/video/reverse-engineer-video/SKILL.md on GitHub (opens in a new tab)

• rough-cut

  Trim the fat from raw talking footage. Turns raw video into a tight first cut by removing dead air, ums and uhs, stutters, false starts and bad takes (keeping the last good take), then checks the result by listening to it again. Use when the user says "rough cut", "first cut", "trim the fat", "cut the pauses", "remove the ums", "cut my retakes", "make it snappy", or hands over raw footage to edit.

  skills/video/rough-cut/SKILL.md on GitHub (opens in a new tab)

• scripted-screencast

  Turn a browser product demo written as a script (click, type, hover, scroll, zoom, caption) into a polished Screen Studio style recording. You get a smooth human-like cursor, click ripples, automatic zoom on small targets, typing at human speed, a padded background with a rounded window frame, burned-in captions and an optional 9:16 version that follows the cursor. It is frame-perfect and needs n…

  skills/video/scripted-screencast/SKILL.md on GitHub (opens in a new tab)

• vox-explainer

  Make Vox-style explainer graphics or a full faceless explainer video, in the user's chosen "style C" (navy and red colour blocks, torn cream paper cards, condensed uppercase headlines, serif quotes, yellow highlighter, black mono label strips, light grain). Every beat, highlight and list item is timed to the exact word in the voiceover. Use when asked for a Vox-style video, explainer graphics, an…

  skills/video/vox-explainer/SKILL.md on GitHub (opens in a new tab)

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