Collection of Claude Skills for Indie Developers - Here's What I Learned

A developer built four single-HTML-file tools—DarkenAmber IT Tools, ZeroOffice, PrivacyKit, and ElectroKit—to demonstrate offline-first, zero-dependency web apps. Frustrated with AI coding assistants defaulting to React and npm setups, they created two reusable Claude skills: 'single-file-app' for building complete tools in one HTML file, and 'ship-it' for prioritizing shipping over planning in early-stage MVPs. The skills are available as Markdown files with YAML frontmatter, designed to advise rather than dictate decisions.

A few months ago I started building small tools as single HTML files - no npm, no React, no backend. Just one file that opens in a browser and works offline. I built 4 real products this way: DarkenAmber IT Tools - 17+ developer tools in 194KB ZeroOffice - PDF, image, AI tools in one file PrivacyKit - Photo privacy tools, no upload required ElectroKit - Electrical calculator + cost estimates for CIS market Every single one: one .html file. Works offline. Opens instantly. No server. The problem with AI coding assistants Every time I asked Claude or Copilot to build something simple, I got: A React project with src/ folder package.json with 12 dependencies webpack config TypeScript setup ...before writing a single line of actual logic. I kept manually correcting it. "No, one file. No npm. Vanilla JS." Then I realized - I should just teach it once and reuse that knowledge. What is a Claude Skill? A skill is a Markdown file with YAML frontmatter that changes how Claude thinks for a specific context. It is not a prompt. It is not a system message. It is a reusable set of rules that shapes how Claude reasons, what it prioritizes, and what it avoids. yaml--- name: single-file-app description: "Build complete web tools as a single HTML file - vanilla JS, inline CSS, localStorage, offline-first." tags: The two skills I built Teaches Claude to build complete web tools in one HTML file. What changes: No React, no npm, no build tools unless truly justified Vanilla JS first, always localStorage for data persistence Dark/light theme with system preference detection Accessibility built in labels, aria, keyboard nav XSS prevention for user input Export/import for user data Anti-patterns it prevents: ❌ "Let me set up a React project" ❌ Creating src/ folder for a simple tool ❌ Suggesting npm install for a calculator ✅ "Here is your complete HTML file" Teaches Claude to bias toward shipping over planning for early-stage MVPs. What it does: Shows trade-offs instead of blocking decisions Cuts scope to what proves the core idea Knows when NOT to apply payments, auth, licensing, irreversible ops The trade-off table not a blocking table : User saysClaude shows"We should make it scalable""Scalability now means X days extra. You have few or no users. Want to spend that on scale or first users?""Let me refactor before shipping""Refactor now cleaner, delayed feedback or ship and refactor if users return faster validation, messier code . Your call." The key insight: a skill should be an advisor, not a saboteur. How to install Claude Code bash single-file-app curl -o CLAUDE.md https://raw.githubusercontent.com/DarkenAmber/claude-skills/main/single-file-app/SKILL.md https://raw.githubusercontent.com/DarkenAmber/claude-skills/main/single-file-app/SKILL.md curl https://raw.githubusercontent.com/DarkenAmber/claude-skills/main/single-file-app/SKILL.md https://raw.githubusercontent.com/DarkenAmber/claude-skills/main/single-file-app/SKILL.md CLAUDE.md curl https://raw.githubusercontent.com/DarkenAmber/claude-skills/main/ship-it/SKILL.md https://raw.githubusercontent.com/DarkenAmber/claude-skills/main/ship-it/SKILL.md CLAUDE.md Claude.ai Projects Copy the contents of any SKILL.md into your Project Instructions. What I learned building these Early version of ship-it had a table that said "We need tests before launching" → "Smoke test manually, write tests after validation". This is the skill making a decision for you. Bad. Better: show the cost of each option and let the developer decide. The most valuable part of ship-it is not the rules - it is the Do NOT use when section: Payments and billing Auth and licensing Irreversible data operations Without this, the skill would tell you to skip tests on your payment module. That is dangerous. When you cannot split into components, you think harder about what actually needs to exist. Every line earns its place. Both skills went through 3+ review rounds. Each round caught something the previous missed. The process itself demonstrated ship-it's philosophy - ship early, iterate on feedback. The repo github.com/DarkenAmber/claude-skills Two skills, MIT license, open to contributions. If you build something with these - I would love to see it. What rules do you give your AI coding assistant? Do you have a CLAUDE.md or .cursorrules file you swear by?