Add some docs

README.md

@@ -1,3 +1,47 @@
 # tally-counter
 
-a tally counter app
+A self-hosted tally counter web app. Create counters, organise them into groups, track history, and view stats.
+
+## Features
+
+- Create, edit, and delete counters with optional photos
+- Organise counters into groups with drag-and-drop reordering
+- Per-counter history modal — streak stats, 90-day chart, activity calendar
+- Global stats page with top counters and 12-month calendar
+- Counters can't go below 0
+- Hover-to-prefetch on history modal for instant opens
+- Fully persistent via SQLite (better-sqlite3, WAL mode)
+
+## Tech stack
+
+- **Next.js 16** — App Router, TypeScript, standalone output
+- **Tailwind CSS v4** — Catppuccin Mocha theme
+- **better-sqlite3** — embedded SQLite, no external database needed
+- **@dnd-kit** — drag-and-drop for counters and groups
+
+## Running locally
+
+```bash
+npm install
+npm run dev
+```
+
+Open [http://localhost:3000](http://localhost:3000).
+
+Data is stored in `.data/` (SQLite DB + uploaded images).
+
+## Docker
+
+```bash
+docker build -t tally-counter .
+docker run -p 3000:3000 -v tally_data:/data tally-counter
+```
+
+The `/data` volume holds both the database and uploaded images. Mount it to persist data across container restarts.
+
+## Environment variables
+
+| Variable   | Default              | Description                        |
+|------------|----------------------|------------------------------------|
+| `DATA_DIR` | `.data` (dev) / `/data` (Docker) | Directory for SQLite DB and uploads |
+| `PORT`     | `3000`               | HTTP port                          |