diff --git a/src/quartermaster/main.py b/src/quartermaster/main.py
new file mode 100644
index 0000000..3c1a2ad
--- /dev/null
+++ b/src/quartermaster/main.py
@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from fastapi import FastAPI
+from fastapi.staticfiles import StaticFiles
+
+from quartermaster.routes import router
+
+STATIC_DIR = Path(__file__).parent / "static"
+
+
+def create_app() -> FastAPI:
+    app = FastAPI(title="Quartermaster", version="0.1.0")
+    app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")
+    app.include_router(router)
+    return app
+
+
+app = create_app()
diff --git a/src/quartermaster/routes.py b/src/quartermaster/routes.py
new file mode 100644
index 0000000..eb7c6c9
--- /dev/null
+++ b/src/quartermaster/routes.py
@@ -0,0 +1,133 @@
+from __future__ import annotations
+
+from decimal import Decimal, InvalidOperation
+from pathlib import Path
+
+from fastapi import APIRouter, Depends, Form, HTTPException, Request
+from fastapi.responses import HTMLResponse
+from fastapi.templating import Jinja2Templates
+from sqlalchemy.orm import Session
+
+from quartermaster import service
+from quartermaster.db import get_session
+from quartermaster.models import SECTION_LABELS, Section
+
+TEMPLATES_DIR = Path(__file__).parent / "templates"
+templates = Jinja2Templates(directory=str(TEMPLATES_DIR))
+
+router = APIRouter()
+
+
+def _parse_amount(raw: str) -> Decimal:
+    try:
+        amount = Decimal(raw.strip())
+    except (InvalidOperation, AttributeError) as exc:
+        raise HTTPException(status_code=400, detail="amount must be numeric") from exc
+    if amount < 0:
+        raise HTTPException(status_code=400, detail="amount must be non-negative")
+    return amount.quantize(Decimal("0.01"))
+
+
+def _section_view(db: Session, section: Section) -> service.SectionView:
+    entries = service.list_entries(db, section)
+    return service.SectionView(
+        section=section,
+        label=SECTION_LABELS[section],
+        entries=entries,
+        total=service.section_total(entries),
+    )
+
+
+def _render_section(
+    request: Request, db: Session, section: Section
+) -> HTMLResponse:
+    view = _section_view(db, section)
+    return templates.TemplateResponse(
+        request, "partials/section.html", {"section": view}
+    )
+
+
+def _render_target(request: Request, db: Session) -> HTMLResponse:
+    target = service.get_debt_target(db)
+    debt_minimums = service.list_entries(db, Section.debt_minimum)
+    return templates.TemplateResponse(
+        request,
+        "partials/target_card.html",
+        {"target": target, "debt_minimums": debt_minimums},
+    )
+
+
+@router.get("/", response_class=HTMLResponse)
+def index(request: Request, db: Session = Depends(get_session)) -> HTMLResponse:
+    sections = [_section_view(db, s) for s in Section]
+    target = service.get_debt_target(db)
+    debt_minimums = service.list_entries(db, Section.debt_minimum)
+    return templates.TemplateResponse(
+        request,
+        "index.html",
+        {
+            "sections": sections,
+            "target": target,
+            "debt_minimums": debt_minimums,
+        },
+    )
+
+
+@router.post("/sections/{section}/entries", response_class=HTMLResponse)
+def create_entry(
+    section: Section,
+    request: Request,
+    name: str = Form(...),
+    amount: str = Form(...),
+    db: Session = Depends(get_session),
+) -> HTMLResponse:
+    clean_name = name.strip()
+    if not clean_name:
+        raise HTTPException(status_code=400, detail="name is required")
+    parsed = _parse_amount(amount)
+    service.add_entry(db, section, clean_name, parsed)
+    response = _render_section(request, db, section)
+    if section == Section.debt_minimum:
+        target_html = _render_target(request, db).body.decode()
+        response = HTMLResponse(response.body.decode() + target_html)
+    return response
+
+
+@router.delete("/entries/{entry_id}", response_class=HTMLResponse)
+def remove_entry(
+    entry_id: int,
+    request: Request,
+    db: Session = Depends(get_session),
+) -> HTMLResponse:
+    entry = service.delete_entry(db, entry_id)
+    if entry is None:
+        raise HTTPException(status_code=404, detail="entry not found")
+    response = _render_section(request, db, entry.section)
+    if entry.section == Section.debt_minimum:
+        target_html = _render_target(request, db).body.decode()
+        response = HTMLResponse(response.body.decode() + target_html)
+    return response
+
+
+@router.post("/debt-target", response_class=HTMLResponse)
+def update_debt_target(
+    request: Request,
+    debt_minimum_id: str = Form(""),
+    db: Session = Depends(get_session),
+) -> HTMLResponse:
+    raw = debt_minimum_id.strip()
+    target_id: int | None
+    if raw == "":
+        target_id = None
+    else:
+        try:
+            target_id = int(raw)
+        except ValueError as exc:
+            raise HTTPException(
+                status_code=400, detail="debt_minimum_id must be an integer"
+            ) from exc
+    try:
+        service.set_debt_target(db, target_id)
+    except ValueError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    return _render_target(request, db)
diff --git a/src/quartermaster/service.py b/src/quartermaster/service.py
new file mode 100644
index 0000000..e5fb3ca
--- /dev/null
+++ b/src/quartermaster/service.py
@@ -0,0 +1,65 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from decimal import Decimal
+
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from quartermaster.models import DebtTarget, Entry, Section
+
+
+@dataclass(frozen=True)
+class SectionView:
+    section: Section
+    label: str
+    entries: list[Entry]
+    total: Decimal
+
+
+def list_entries(db: Session, section: Section) -> list[Entry]:
+    stmt = select(Entry).where(Entry.section == section).order_by(Entry.id)
+    return list(db.scalars(stmt))
+
+
+def section_total(entries: list[Entry]) -> Decimal:
+    return sum((e.amount for e in entries), Decimal("0"))
+
+
+def add_entry(db: Session, section: Section, name: str, amount: Decimal) -> Entry:
+    entry = Entry(section=section, name=name.strip(), amount=amount)
+    db.add(entry)
+    db.commit()
+    db.refresh(entry)
+    return entry
+
+
+def delete_entry(db: Session, entry_id: int) -> Entry | None:
+    entry = db.get(Entry, entry_id)
+    if entry is None:
+        return None
+    db.delete(entry)
+    db.commit()
+    return entry
+
+
+def get_debt_target(db: Session) -> DebtTarget:
+    target = db.get(DebtTarget, 1)
+    if target is None:
+        target = DebtTarget(id=1, debt_minimum_id=None)
+        db.add(target)
+        db.commit()
+        db.refresh(target)
+    return target
+
+
+def set_debt_target(db: Session, debt_minimum_id: int | None) -> DebtTarget:
+    target = get_debt_target(db)
+    if debt_minimum_id is not None:
+        candidate = db.get(Entry, debt_minimum_id)
+        if candidate is None or candidate.section != Section.debt_minimum:
+            raise ValueError("debt_minimum_id must reference a debt minimum entry")
+    target.debt_minimum_id = debt_minimum_id
+    db.commit()
+    db.refresh(target)
+    return target
diff --git a/src/quartermaster/static/app.css b/src/quartermaster/static/app.css
new file mode 100644
index 0000000..98d8ba1
--- /dev/null
+++ b/src/quartermaster/static/app.css
@@ -0,0 +1,160 @@
+:root {
+  --bg: #f7f6f2;
+  --card: #ffffff;
+  --ink: #1f1f1f;
+  --muted: #6b6b6b;
+  --accent: #2f6b4f;
+  --danger: #a03030;
+  --border: #d8d6cf;
+}
+
+* { box-sizing: border-box; }
+
+body {
+  margin: 0;
+  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
+  color: var(--ink);
+  background: var(--bg);
+  line-height: 1.4;
+}
+
+header {
+  padding: 1.5rem 2rem 0.5rem;
+}
+
+header h1 {
+  margin: 0;
+  font-size: 1.6rem;
+}
+
+.subtitle {
+  margin: 0;
+  color: var(--muted);
+}
+
+main {
+  padding: 1rem 2rem 2rem;
+}
+
+.grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
+  gap: 1rem;
+}
+
+.card {
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  padding: 1rem;
+  display: flex;
+  flex-direction: column;
+  gap: 0.75rem;
+}
+
+.card-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: baseline;
+}
+
+.card-header h2 {
+  margin: 0;
+  font-size: 1.1rem;
+}
+
+.total {
+  font-variant-numeric: tabular-nums;
+  font-weight: 600;
+  color: var(--accent);
+}
+
+ul.entries {
+  list-style: none;
+  padding: 0;
+  margin: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 0.25rem;
+}
+
+.entry {
+  display: grid;
+  grid-template-columns: 1fr auto auto;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.35rem 0.5rem;
+  border-radius: 4px;
+  background: #fafaf7;
+}
+
+.entry-amount {
+  font-variant-numeric: tabular-nums;
+  color: var(--muted);
+}
+
+.empty {
+  color: var(--muted);
+  font-style: italic;
+}
+
+button.delete {
+  background: transparent;
+  border: none;
+  color: var(--danger);
+  font-size: 1rem;
+  cursor: pointer;
+  padding: 0 0.35rem;
+}
+
+.add-form,
+.target-form {
+  display: grid;
+  grid-template-columns: 1fr 7rem auto;
+  gap: 0.5rem;
+}
+
+.target-form {
+  grid-template-columns: 1fr auto;
+  align-items: center;
+}
+
+.target-form label {
+  grid-column: 1 / -1;
+  font-size: 0.85rem;
+  color: var(--muted);
+}
+
+.target-current {
+  margin: 0;
+  padding: 0.5rem 0.75rem;
+  background: #f0ece0;
+  border-radius: 4px;
+  display: flex;
+  justify-content: space-between;
+}
+
+.target-current.empty {
+  color: var(--muted);
+  font-style: italic;
+}
+
+input[type=text],
+input[type=number],
+select {
+  padding: 0.35rem 0.5rem;
+  border: 1px solid var(--border);
+  border-radius: 4px;
+  font: inherit;
+  background: #fff;
+}
+
+button[type=submit] {
+  padding: 0.35rem 0.75rem;
+  background: var(--accent);
+  color: #fff;
+  border: none;
+  border-radius: 4px;
+  cursor: pointer;
+  font: inherit;
+}
diff --git a/src/quartermaster/templates/base.html b/src/quartermaster/templates/base.html
new file mode 100644
index 0000000..807588b
--- /dev/null
+++ b/src/quartermaster/templates/base.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width,initial-scale=1">
+  <title>Quartermaster</title>
+  <link rel="stylesheet" href="{{ url_for('static', path='app.css') }}">
+  <script src="https://unpkg.com/htmx.org@2.0.3" defer></script>
+</head>
+<body>
+  <header>
+    <h1>Quartermaster</h1>
+    <p class="subtitle">Household budget</p>
+  </header>
+  <main>
+    {% block content %}{% endblock %}
+  </main>
+</body>
+</html>
diff --git a/src/quartermaster/templates/index.html b/src/quartermaster/templates/index.html
new file mode 100644
index 0000000..96dc563
--- /dev/null
+++ b/src/quartermaster/templates/index.html
@@ -0,0 +1,9 @@
+{% extends "base.html" %}
+{% block content %}
+<div class="grid">
+  {% for section in sections %}
+    {% include "partials/section.html" %}
+  {% endfor %}
+  {% include "partials/target_card.html" %}
+</div>
+{% endblock %}
diff --git a/src/quartermaster/templates/partials/section.html b/src/quartermaster/templates/partials/section.html
new file mode 100644
index 0000000..1c091a7
--- /dev/null
+++ b/src/quartermaster/templates/partials/section.html
@@ -0,0 +1,37 @@
+<section class="card" id="section-{{ section.section.value }}">
+  <header class="card-header">
+    <h2>{{ section.label }}</h2>
+    <span class="total" data-testid="total-{{ section.section.value }}">
+      ${{ '%.2f' | format(section.total) }}
+    </span>
+  </header>
+  <ul class="entries">
+    {% for entry in section.entries %}
+      <li class="entry">
+        <span class="entry-name">{{ entry.name }}</span>
+        <span class="entry-amount">${{ '%.2f' | format(entry.amount) }}</span>
+        <button
+          class="delete"
+          type="button"
+          hx-delete="/entries/{{ entry.id }}"
+          hx-target="#section-{{ section.section.value }}"
+          hx-swap="outerHTML"
+          aria-label="Delete {{ entry.name }}"
+        >&times;</button>
+      </li>
+    {% else %}
+      <li class="empty">No entries yet.</li>
+    {% endfor %}
+  </ul>
+  <form
+    class="add-form"
+    hx-post="/sections/{{ section.section.value }}/entries"
+    hx-target="#section-{{ section.section.value }}"
+    hx-swap="outerHTML"
+    hx-on::after-request="if(event.detail.successful) this.reset()"
+  >
+    <input type="text" name="name" placeholder="Name" required>
+    <input type="number" name="amount" step="0.01" min="0" placeholder="0.00" required>
+    <button type="submit">Add</button>
+  </form>
+</section>
diff --git a/src/quartermaster/templates/partials/target_card.html b/src/quartermaster/templates/partials/target_card.html
new file mode 100644
index 0000000..3d513b3
--- /dev/null
+++ b/src/quartermaster/templates/partials/target_card.html
@@ -0,0 +1,31 @@
+<section class="card target-card" id="section-debt_target" hx-swap-oob="outerHTML">
+  <header class="card-header">
+    <h2>Primary Debt Target</h2>
+  </header>
+  {% if target.entry %}
+    <p class="target-current">
+      <span class="entry-name">{{ target.entry.name }}</span>
+      <span class="entry-amount">${{ '%.2f' | format(target.entry.amount) }}</span>
+    </p>
+  {% else %}
+    <p class="target-current empty">No target selected.</p>
+  {% endif %}
+  <form
+    class="target-form"
+    hx-post="/debt-target"
+    hx-target="#section-debt_target"
+    hx-swap="outerHTML"
+  >
+    <label for="debt-target-select">Choose from Debt Minimums</label>
+    <select id="debt-target-select" name="debt_minimum_id">
+      <option value="">(none)</option>
+      {% for dm in debt_minimums %}
+        <option
+          value="{{ dm.id }}"
+          {% if target.debt_minimum_id == dm.id %}selected{% endif %}
+        >{{ dm.name }}: ${{ '%.2f' | format(dm.amount) }}</option>
+      {% endfor %}
+    </select>
+    <button type="submit">Set</button>
+  </form>
+</section>