diff --git a/docs/dev.md b/docs/dev.md
new file mode 100644
index 0000000..ab5ddd7
--- /dev/null
+++ b/docs/dev.md
@@ -0,0 +1,18 @@
+# Local development
+
+## Run
+
+ go run .
+
+The server listens on http://localhost:8080 (override with `PORT`). Templates, static assets, and sample data are read from disk on every request — edit a file and refresh the browser; no restart needed.
+
+## Local data
+
+The server reads local data from `sampledata/`, mirroring the production Sheets layout: one directory per app, one CSV file per table, first row is the schema. It goes through the same data-source interface production backends implement, so app code never knows which backend it is talking to.
+
+## Layout
+
+- `main.go` — server entry point and app routing
+- `internal/data` — data source interface and the CSV sample-data implementation
+- `internal/directory` — directory app handlers
+- `web/directory` — directory app page templates and static assets
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f54468d
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module heliosian
+
+go 1.26
diff --git a/internal/data/data.go b/internal/data/data.go
new file mode 100644
index 0000000..d469cce
--- /dev/null
+++ b/internal/data/data.go
@@ -0,0 +1,42 @@
+// Package data provides tabular app data sources.
+package data
+
+import (
+ "encoding/csv"
+ "fmt"
+ "os"
+ "path/filepath"
+)
+
+type Source interface {
+ Table(app, name string) ([]map[string]string, error)
+}
+
+type Dir struct {
+ Root string
+}
+
+func (d Dir) Table(app, name string) ([]map[string]string, error) {
+ f, err := os.Open(filepath.Join(d.Root, app, name+".csv"))
+ if err != nil {
+ return nil, err
+ }
+ defer f.Close()
+ rows, err := csv.NewReader(f).ReadAll()
+ if err != nil {
+ return nil, err
+ }
+ if len(rows) == 0 {
+ return nil, fmt.Errorf("table %s/%s has no header row", app, name)
+ }
+ header := rows[0]
+ records := []map[string]string{}
+ for _, row := range rows[1:] {
+ record := map[string]string{}
+ for i, column := range header {
+ record[column] = row[i]
+ }
+ records = append(records, record)
+ }
+ return records, nil
+}
diff --git a/internal/directory/directory.go b/internal/directory/directory.go
new file mode 100644
index 0000000..58c1391
--- /dev/null
+++ b/internal/directory/directory.go
@@ -0,0 +1,102 @@
+// Package directory serves the school directory app.
+package directory
+
+import (
+ "encoding/json"
+ "fmt"
+ "html/template"
+ "log"
+ "net/http"
+ "sort"
+
+ "heliosian/internal/data"
+)
+
+type app struct {
+ source data.Source
+}
+
+func Register(mux *http.ServeMux, source data.Source) {
+ a := app{source: source}
+ mux.HandleFunc("GET /directory/{$}", a.index)
+ mux.HandleFunc("GET /directory/api/people", a.people)
+ mux.Handle("GET /directory/static/", http.StripPrefix("/directory/static/", http.FileServer(http.Dir("web/directory/static"))))
+}
+
+func (a app) index(w http.ResponseWriter, r *http.Request) {
+ t, err := template.ParseFiles("web/directory/index.html")
+ if err != nil {
+ serverError(w, err)
+ return
+ }
+ if err := t.Execute(w, nil); err != nil {
+ log.Printf("[ERROR] render directory index: %v", err)
+ }
+}
+
+type person struct {
+ ID string `json:"id"`
+ FirstName string `json:"firstName"`
+ LastName string `json:"lastName"`
+ Role string `json:"role"`
+ Grade string `json:"grade"`
+ Email string `json:"email"`
+ Phone string `json:"phone"`
+ Pronunciation string `json:"pronunciation"`
+ FamilyName string `json:"familyName"`
+ Address string `json:"address"`
+ FamilyPhone string `json:"familyPhone"`
+}
+
+func (a app) people(w http.ResponseWriter, r *http.Request) {
+ families, err := a.source.Table("directory", "families")
+ if err != nil {
+ serverError(w, err)
+ return
+ }
+ familiesByID := map[string]map[string]string{}
+ for _, family := range families {
+ familiesByID[family["id"]] = family
+ }
+ rows, err := a.source.Table("directory", "people")
+ if err != nil {
+ serverError(w, err)
+ return
+ }
+ people := []person{}
+ for _, row := range rows {
+ family, ok := familiesByID[row["family_id"]]
+ if !ok {
+ serverError(w, fmt.Errorf("person %s has unknown family_id %q", row["id"], row["family_id"]))
+ return
+ }
+ people = append(people, person{
+ ID: row["id"],
+ FirstName: row["first_name"],
+ LastName: row["last_name"],
+ Role: row["role"],
+ Grade: row["grade"],
+ Email: row["email"],
+ Phone: row["phone"],
+ Pronunciation: row["pronunciation"],
+ FamilyName: family["name"],
+ Address: family["address"],
+ FamilyPhone: family["phone"],
+ })
+ }
+ sort.Slice(people, func(i, j int) bool {
+ if people[i].LastName != people[j].LastName {
+ return people[i].LastName < people[j].LastName
+ }
+ return people[i].FirstName < people[j].FirstName
+ })
+ w.Header().Set("Content-Type", "application/json")
+ if err := json.NewEncoder(w).Encode(people); err != nil {
+ log.Printf("[ERROR] encode people: %v", err)
+ }
+}
+
+func serverError(w http.ResponseWriter, err error) {
+ log.Printf("[ERROR] %v", err)
+ http.Error(w, "internal error", http.StatusInternalServerError)
+}
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..5f67ee0
--- /dev/null
+++ b/main.go
@@ -0,0 +1,23 @@
+// Heliosian serves the Helios school community apps.
+package main
+
+import (
+ "log"
+ "net/http"
+ "os"
+
+ "heliosian/internal/data"
+ "heliosian/internal/directory"
+)
+
+func main() {
+ mux := http.NewServeMux()
+ directory.Register(mux, data.Dir{Root: "sampledata"})
+ mux.Handle("GET /{$}", http.RedirectHandler("/directory/", http.StatusFound))
+ port := os.Getenv("PORT")
+ if port == "" {
+ port = "8080"
+ }
+ log.Printf("listening on http://localhost:%s", port)
+ log.Fatal(http.ListenAndServe(":"+port, mux))
+}
diff --git a/web/directory/index.html b/web/directory/index.html
new file mode 100644
index 0000000..b15016d
--- /dev/null
+++ b/web/directory/index.html
@@ -0,0 +1,17 @@
+
+
+
+
+
+Helios Directory
+
+
+
+
+
+
+
+
diff --git a/web/directory/static/app.js b/web/directory/static/app.js
new file mode 100644
index 0000000..bb41c0a
--- /dev/null
+++ b/web/directory/static/app.js
@@ -0,0 +1,68 @@
+const state = {people: []};
+
+function hue(text) {
+ let h = 0;
+ for (const c of text) {
+ h = (h * 31 + c.codePointAt(0)) % 360;
+ }
+ return h;
+}
+
+function el(tag, className, text) {
+ const node = document.createElement(tag);
+ if (className) {
+ node.className = className;
+ }
+ if (text) {
+ node.textContent = text;
+ }
+ return node;
+}
+
+function card(p) {
+ const root = el('div', 'card');
+ const avatar = el('div', 'avatar', (p.firstName[0] || '') + (p.lastName[0] || ''));
+ avatar.style.background = `hsl(${hue(p.firstName + p.lastName)} 60% 45%)`;
+ root.append(avatar);
+ const info = el('div');
+ info.append(el('div', 'name', `${p.firstName} ${p.lastName}`));
+ if (p.pronunciation) {
+ info.append(el('div', 'pronunciation', p.pronunciation));
+ }
+ const who = p.role === 'student' ? `Student, grade ${p.grade}` : 'Parent';
+ info.append(el('div', 'detail', `${who} · ${p.familyName}`));
+ info.append(el('div', 'detail', p.address));
+ const contact = [p.phone || p.familyPhone, p.email].filter(Boolean).join(' · ');
+ if (contact) {
+ info.append(el('div', 'detail', contact));
+ }
+ root.append(info);
+ return root;
+}
+
+function render() {
+ const q = document.querySelector('#search').value.trim().toLowerCase();
+ const list = document.querySelector('#people');
+ list.replaceChildren();
+ const matches = state.people.filter(p =>
+ `${p.firstName} ${p.lastName} ${p.familyName}`.toLowerCase().includes(q));
+ if (matches.length === 0) {
+ list.append(el('div', 'empty', 'No matches.'));
+ return;
+ }
+ for (const p of matches) {
+ list.append(card(p));
+ }
+}
+
+async function load() {
+ const res = await fetch('/directory/api/people');
+ if (!res.ok) {
+ throw new Error(`loading people failed: ${res.status}`);
+ }
+ state.people = await res.json();
+ render();
+}
+
+document.querySelector('#search').addEventListener('input', render);
+load();
diff --git a/web/directory/static/style.css b/web/directory/static/style.css
new file mode 100644
index 0000000..278c6d7
--- /dev/null
+++ b/web/directory/static/style.css
@@ -0,0 +1,96 @@
+:root {
+ --bg: #f6f7f9;
+ --card: #ffffff;
+ --line: #e2e6eb;
+ --text: #1c2430;
+ --muted: #5b6572;
+}
+
+* {
+ box-sizing: border-box;
+}
+
+body {
+ margin: 0;
+ font-family: system-ui, sans-serif;
+ background: var(--bg);
+ color: var(--text);
+}
+
+header {
+ position: sticky;
+ top: 0;
+ background: var(--card);
+ border-bottom: 1px solid var(--line);
+ padding: 1rem 1.5rem;
+ display: flex;
+ align-items: center;
+ gap: 1.5rem;
+}
+
+header h1 {
+ font-size: 1.25rem;
+ margin: 0;
+}
+
+#search {
+ flex: 1;
+ max-width: 24rem;
+ padding: 0.5rem 0.75rem;
+ border: 1px solid #cdd3db;
+ border-radius: 0.5rem;
+ font-size: 1rem;
+}
+
+#people {
+ display: grid;
+ grid-template-columns: repeat(auto-fill, minmax(17rem, 1fr));
+ gap: 1rem;
+ padding: 1.5rem;
+ max-width: 72rem;
+ margin: 0 auto;
+}
+
+.card {
+ background: var(--card);
+ border: 1px solid var(--line);
+ border-radius: 0.75rem;
+ padding: 1rem;
+ display: flex;
+ gap: 0.75rem;
+}
+
+.avatar {
+ width: 3rem;
+ height: 3rem;
+ border-radius: 50%;
+ color: white;
+ display: flex;
+ align-items: center;
+ justify-content: center;
+ font-weight: 600;
+ flex-shrink: 0;
+}
+
+.name {
+ font-weight: 600;
+}
+
+.pronunciation {
+ color: var(--muted);
+ font-style: italic;
+ font-size: 0.875rem;
+}
+
+.detail {
+ color: var(--muted);
+ font-size: 0.875rem;
+ margin-top: 0.25rem;
+}
+
+.empty {
+ color: var(--muted);
+ padding: 3rem;
+ text-align: center;
+ grid-column: 1 / -1;
+}