diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..fc94470
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,34 @@
+.PHONY: build build-web build-go dev test clean
+
+# Build the production single binary (embeds the Svelte SPA)
+build: build-web build-go
+
+build-web:
+	@echo "==> Building Svelte frontend..."
+	cd web && npm run build
+
+build-go:
+	@echo "==> Building Go binary (production, embeds web/build)..."
+	go build -tags production -o wotra ./cmd/wotra
+
+# Development mode: run Go server + Vite dev server concurrently
+dev:
+	@echo "==> Starting development servers..."
+	@echo "    Go API:  http://localhost:8080"
+	@echo "    Vite UI: http://localhost:5173"
+	@trap 'kill 0' INT; \
+	  AUTH_TOKEN=$${AUTH_TOKEN:-devtoken} go run ./cmd/wotra & \
+	  cd web && npm run dev
+
+# Run all Go tests
+test:
+	go test ./...
+
+# Install frontend dependencies
+web/node_modules:
+	cd web && npm install
+
+# Remove build artifacts
+clean:
+	rm -f wotra
+	rm -rf web/build web/.svelte-kit
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a31a254
--- /dev/null
+++ b/README.md
@@ -0,0 +1,132 @@
+# Wotra — Working Time Tracker
+
+A self-hosted working time tracker with a Go backend and a Svelte PWA frontend. Offline-capable, single-binary deploy.
+
+## Features
+
+- **Start / Stop** time tracking with an optional note.
+- **Close days**: merges all entries (worked_ms = sum of durations, breaks excluded).
+- **Mark days** as holiday, vacation, or sick (auto-credits expected daily hours).
+- **Close weeks**: computes overtime/undertime against a frozen snapshot of your expected hours.
+- **Settings history**: change hours/week with an `effective_from` date — past closed weeks are unaffected.
+- **PWA + offline**: works without a network connection; syncs via IndexedDB outbox when back online.
+- **CSV export**: entries, days, weeks.
+- **Midnight guard**: running entries are automatically stopped at 23:59:59 if they cross midnight.
+
+## Quick Start
+
+### Development
+
+```bash
+# 1. Set your auth token
+export AUTH_TOKEN=mysecrettoken
+
+# 2. Start both servers
+make dev
+# Go API:  http://localhost:8080
+# Vite UI: http://localhost:5173 (with /api proxy)
+```
+
+Open `http://localhost:5173`, go to **Settings**, enter your token.
+
+### Production (single binary)
+
+```bash
+make build           # builds web/ then embeds it in the Go binary
+
+# Run
+AUTH_TOKEN=mysecrettoken ./wotra
+# open http://localhost:8080
+```
+
+## Configuration (environment variables)
+
+| Variable     | Default     | Description                                  |
+|-------------|-------------|----------------------------------------------|
+| `AUTH_TOKEN` | **required** | Bearer token for API access                  |
+| `PORT`       | `8080`       | HTTP port                                    |
+| `DB_PATH`    | `wotra.db`   | SQLite database file path                    |
+| `TZ`         | `UTC`        | Timezone for day/week key calculation        |
+
+## API Reference
+
+All API endpoints require `Authorization: Bearer <token>` except `/healthz`.
+
+### Entries
+
+| Method | Path                        | Description              |
+|--------|-----------------------------|--------------------------|
+| POST   | `/api/entries/start`        | Start tracking           |
+| POST   | `/api/entries/{id}/stop`    | Stop a specific entry    |
+| GET    | `/api/entries?from=&to=`    | List entries by date     |
+| PUT    | `/api/entries/{id}`         | Edit start/end/note      |
+| DELETE | `/api/entries/{id}`         | Soft-delete an entry     |
+
+### Days
+
+| Method | Path                          | Description                          |
+|--------|-------------------------------|--------------------------------------|
+| GET    | `/api/days?from=&to=`         | List closed days                     |
+| POST   | `/api/days/{day}/close`       | Close a day (merge entries)          |
+| POST   | `/api/days/{day}/mark`        | Mark as holiday/vacation/sick        |
+| DELETE | `/api/days/{day}/close`       | Reopen a closed day                  |
+
+### Weeks
+
+| Method | Path                          | Description                          |
+|--------|-------------------------------|--------------------------------------|
+| GET    | `/api/weeks?from=&to=`        | List closed weeks                    |
+| POST   | `/api/weeks/{week}/close`     | Close a week (compute overtime)      |
+| DELETE | `/api/weeks/{week}/close`     | Reopen a closed week                 |
+
+Week key format: `YYYY-Www` (e.g. `2024-W03`).
+
+### Settings
+
+| Method | Path                    | Description                        |
+|--------|-------------------------|------------------------------------|
+| GET    | `/api/settings`         | Current effective settings         |
+| PUT    | `/api/settings`         | Add a new settings version         |
+| GET    | `/api/settings/history` | All settings history               |
+
+### Export
+
+| Method | Path                         | Description              |
+|--------|------------------------------|--------------------------|
+| GET    | `/api/export/entries.csv`    | Export entries as CSV    |
+| GET    | `/api/export/days.csv`       | Export days as CSV       |
+| GET    | `/api/export/weeks.csv`      | Export weeks as CSV      |
+
+### Sync
+
+| Method | Path              | Description                         |
+|--------|-------------------|-------------------------------------|
+| POST   | `/api/sync/pull`  | Pull changes since a version        |
+| POST   | `/api/sync/push`  | Push local changes (advisory)       |
+
+### Health
+
+| Method | Path        | Description              |
+|--------|-------------|--------------------------|
+| GET    | `/healthz`  | Unauthenticated health   |
+
+## Architecture
+
+```
+┌─────────────────────────┐         ┌──────────────────────────┐
+│   Svelte PWA (client)   │ ◄─────► │    Go service (API)      │
+│  - IndexedDB (Dexie)    │  HTTPS  │  - REST/JSON endpoints   │
+│  - Service Worker       │  JSON   │  - Business logic        │
+│  - Sync outbox          │         │  - SQLite (modernc)      │
+└─────────────────────────┘         └──────────────────────────┘
+```
+
+See [PLAN.md](PLAN.md) for the full design document.
+
+## Development Notes
+
+- **Go module**: `github.com/wotra/wotra`
+- **SQLite driver**: `modernc.org/sqlite` (pure Go, no CGO)
+- **Day boundary**: entries must not cross midnight; the server auto-stops any running entry at 23:59:59 local time.
+- **Settings history**: `effective_from` lets you change hours/week without rewriting past closed weeks.
+- **Overtime**: stored as a signed `delta_ms` on each `closed_weeks` row. Frozen at close time.
diff --git a/internal/handler/export_handler.go b/internal/handler/export_handler.go
new file mode 100644
index 0000000..6936f1e
--- /dev/null
+++ b/internal/handler/export_handler.go
@@ -0,0 +1,120 @@
+package handler
+
+import (
+	"encoding/csv"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/wotra/wotra/internal/service"
+)
+
+// ExportHandler serves /api/export routes.
+type ExportHandler struct {
+	entrySvc   *service.EntryService
+	daySvc     *service.DayService
+	weekSvc    *service.WeekService
+}
+
+func NewExportHandler(e *service.EntryService, d *service.DayService, w *service.WeekService) *ExportHandler {
+	return &ExportHandler{entrySvc: e, daySvc: d, weekSvc: w}
+}
+
+func (h *ExportHandler) Routes(r chi.Router) {
+	r.Get("/export/entries.csv", h.EntriesCSV)
+	r.Get("/export/days.csv", h.DaysCSV)
+	r.Get("/export/weeks.csv", h.WeeksCSV)
+}
+
+// EntriesCSV GET /api/export/entries.csv?from=YYYY-MM-DD&to=YYYY-MM-DD
+func (h *ExportHandler) EntriesCSV(w http.ResponseWriter, r *http.Request) {
+	from := r.URL.Query().Get("from")
+	to := r.URL.Query().Get("to")
+	if from == "" { from = "0000-01-01" }
+	if to == "" { to = "9999-12-31" }
+
+	es, err := h.entrySvc.List(r.Context(), from, to)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/csv")
+	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="entries-%s.csv"`, time.Now().Format("20060102")))
+	cw := csv.NewWriter(w)
+	cw.Write([]string{"id", "day_key", "start_time", "end_time", "duration_ms", "note", "auto_stopped"})
+	for _, e := range es {
+		endStr := ""
+		durStr := "0"
+		if e.EndTime != nil {
+			endStr = time.UnixMilli(*e.EndTime).UTC().Format(time.RFC3339)
+			durStr = fmt.Sprintf("%d", *e.EndTime - e.StartTime)
+		}
+		cw.Write([]string{
+			e.ID,
+			e.DayKey,
+			time.UnixMilli(e.StartTime).UTC().Format(time.RFC3339),
+			endStr,
+			durStr,
+			e.Note,
+			fmt.Sprintf("%v", e.AutoStopped),
+		})
+	}
+	cw.Flush()
+}
+
+// DaysCSV GET /api/export/days.csv?from=YYYY-MM-DD&to=YYYY-MM-DD
+func (h *ExportHandler) DaysCSV(w http.ResponseWriter, r *http.Request) {
+	from := r.URL.Query().Get("from")
+	to := r.URL.Query().Get("to")
+	if from == "" { from = "0000-01-01" }
+	if to == "" { to = "9999-12-31" }
+
+	ds, err := h.daySvc.ListDays(r.Context(), from, to)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/csv")
+	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="days-%s.csv"`, time.Now().Format("20060102")))
+	cw := csv.NewWriter(w)
+	cw.Write([]string{"day_key", "kind", "worked_ms", "worked_hours"})
+	for _, d := range ds {
+		workedH := fmt.Sprintf("%.2f", float64(d.WorkedMs)/3_600_000)
+		cw.Write([]string{d.DayKey, string(d.Kind), fmt.Sprintf("%d", d.WorkedMs), workedH})
+	}
+	cw.Flush()
+}
+
+// WeeksCSV GET /api/export/weeks.csv
+func (h *ExportHandler) WeeksCSV(w http.ResponseWriter, r *http.Request) {
+	from := r.URL.Query().Get("from")
+	to := r.URL.Query().Get("to")
+	if from == "" { from = "0000-W01" }
+	if to == "" { to = "9999-W53" }
+
+	ws, err := h.weekSvc.ListWeeks(r.Context(), from, to)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/csv")
+	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="weeks-%s.csv"`, time.Now().Format("20060102")))
+	cw := csv.NewWriter(w)
+	cw.Write([]string{"week_key", "expected_ms", "worked_ms", "delta_ms", "expected_h", "worked_h", "delta_h"})
+	for _, wk := range ws {
+		cw.Write([]string{
+			wk.WeekKey,
+			fmt.Sprintf("%d", wk.ExpectedMs),
+			fmt.Sprintf("%d", wk.WorkedMs),
+			fmt.Sprintf("%d", wk.DeltaMs),
+			fmt.Sprintf("%.2f", float64(wk.ExpectedMs)/3_600_000),
+			fmt.Sprintf("%.2f", float64(wk.WorkedMs)/3_600_000),
+			fmt.Sprintf("%.2f", float64(wk.DeltaMs)/3_600_000),
+		})
+	}
+	cw.Flush()
+}
diff --git a/internal/handler/router.go b/internal/handler/router.go
index f7b0573..8ab116f 100644
--- a/internal/handler/router.go
+++ b/internal/handler/router.go
@@ -49,6 +49,9 @@ func NewRouter(
 
 		syncH := NewSyncHandler(syncStore)
 		syncH.Routes(r)
+
+		exportH := NewExportHandler(entrySvc, daySvc, weekSvc)
+		exportH.Routes(r)
 	})
 
 	// Serve embedded SPA if available (production build)