diff --git a/static/app.js b/static/app.js
new file mode 100644
index 0000000..64055f5
--- /dev/null
+++ b/static/app.js
@@ -0,0 +1,426 @@
+import * as THREE from "three";
+import { OrbitControls } from "three/addons/controls/OrbitControls.js";
+import { STLLoader } from "three/addons/loaders/STLLoader.js";
+import { ThreeMFLoader } from "three/addons/loaders/3MFLoader.js";
+
+const view = document.getElementById("view");
+const crumbs = document.getElementById("crumbs");
+const homeLink = document.getElementById("home-link");
+
+const stlLoader = new STLLoader();
+const mfLoader = new ThreeMFLoader();
+
+let currentProject = null;
+const activeViewers = []; // track for cleanup / resize
+
+// ---------- Routing ----------
+
+homeLink.addEventListener("click", (e) => {
+  e.preventDefault();
+  navigateHome();
+});
+
+function navigateHome() {
+  currentProject = null;
+  crumbs.innerHTML = "";
+  renderDashboard();
+}
+
+function navigateToProject(name) {
+  currentProject = name;
+  crumbs.innerHTML = `<span class="sep">/</span><span class="current"></span>`;
+  crumbs.querySelector(".current").textContent = name;
+  renderProject(name);
+}
+
+// ---------- API helpers ----------
+
+async function api(path, options = {}) {
+  const res = await fetch(path, options);
+  if (!res.ok) {
+    let detail = res.statusText;
+    try {
+      const body = await res.json();
+      detail = body.detail || detail;
+    } catch (_) {}
+    throw new Error(detail);
+  }
+  if (res.status === 204) return null;
+  return res.json();
+}
+
+function showToast(message, isError = false) {
+  const el = document.createElement("div");
+  el.className = "toast" + (isError ? " toast--error" : "");
+  el.textContent = message;
+  document.body.appendChild(el);
+  setTimeout(() => el.remove(), 3000);
+}
+
+function formatSize(bytes) {
+  if (bytes < 1024) return `${bytes} B`;
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
+  return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
+}
+
+// ---------- Dashboard ----------
+
+async function renderDashboard() {
+  view.innerHTML = "";
+
+  const header = document.createElement("div");
+  header.className = "view-header";
+  header.innerHTML = `
+    <div>
+      <h1 class="view-title">Projekte</h1>
+      <div class="view-subtitle">Lege ein Projekt an, um STL- und 3MF-Dateien zu verwalten.</div>
+    </div>
+  `;
+  view.appendChild(header);
+
+  let projects = [];
+  try {
+    projects = await api("/api/projects");
+  } catch (err) {
+    showToast("Projekte konnten nicht geladen werden: " + err.message, true);
+  }
+
+  const grid = document.createElement("div");
+  grid.className = "project-grid";
+
+  const newCardTpl = document.getElementById("tpl-new-project-card");
+  const newCard = newCardTpl.content.firstElementChild.cloneNode(true);
+  newCard.addEventListener("click", () => showNewProjectForm(grid, newCard));
+  grid.appendChild(newCard);
+
+  const cardTpl = document.getElementById("tpl-project-card");
+  for (const project of projects) {
+    const card = cardTpl.content.firstElementChild.cloneNode(true);
+    card.querySelector(".project-card-name").textContent = project.name;
+    card.querySelector(".project-card-meta").textContent =
+      project.file_count === 1 ? "1 Datei" : `${project.file_count} Dateien`;
+    card.addEventListener("click", () => navigateToProject(project.name));
+    grid.appendChild(card);
+  }
+
+  view.appendChild(grid);
+}
+
+function showNewProjectForm(grid, anchorCard) {
+  if (document.querySelector(".new-project-form")) return;
+
+  const form = document.createElement("div");
+  form.className = "new-project-form";
+  form.innerHTML = `
+    <input type="text" placeholder="Projektname" maxlength="80" />
+    <button class="btn" type="button" data-action="create">Anlegen</button>
+    <button class="btn" type="button" data-action="cancel">Abbrechen</button>
+  `;
+  view.insertBefore(form, grid);
+
+  const input = form.querySelector("input");
+  input.focus();
+
+  const cleanup = () => form.remove();
+
+  form.querySelector('[data-action="cancel"]').addEventListener("click", cleanup);
+
+  const submit = async () => {
+    const name = input.value.trim();
+    if (!name) return;
+    try {
+      await api("/api/projects", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ name }),
+      });
+      cleanup();
+      renderDashboard();
+    } catch (err) {
+      showToast("Projekt konnte nicht angelegt werden: " + err.message, true);
+    }
+  };
+
+  form.querySelector('[data-action="create"]').addEventListener("click", submit);
+  input.addEventListener("keydown", (e) => {
+    if (e.key === "Enter") submit();
+    if (e.key === "Escape") cleanup();
+  });
+}
+
+// ---------- Project view ----------
+
+async function renderProject(name) {
+  disposeViewers();
+  view.innerHTML = "";
+
+  const header = document.createElement("div");
+  header.className = "view-header";
+  header.innerHTML = `
+    <div>
+      <h1 class="view-title"></h1>
+      <div class="view-subtitle">STL- und 3MF-Dateien dieses Projekts.</div>
+    </div>
+    <button class="btn btn-danger" type="button" data-action="delete-project">Projekt löschen</button>
+  `;
+  header.querySelector(".view-title").textContent = name;
+  header.querySelector('[data-action="delete-project"]').addEventListener("click", async () => {
+    if (!confirm(`Projekt "${name}" inklusive aller Dateien löschen?`)) return;
+    try {
+      await api(`/api/projects/${encodeURIComponent(name)}`, { method: "DELETE" });
+      navigateHome();
+    } catch (err) {
+      showToast("Löschen fehlgeschlagen: " + err.message, true);
+    }
+  });
+  view.appendChild(header);
+
+  const dropzone = document.createElement("div");
+  dropzone.className = "dropzone";
+  dropzone.innerHTML = `<strong>STL- oder 3MF-Dateien hierher ziehen</strong> oder klicken zum Auswählen`;
+  view.appendChild(dropzone);
+
+  const fileInput = document.createElement("input");
+  fileInput.type = "file";
+  fileInput.multiple = true;
+  fileInput.accept = ".stl,.3mf";
+  fileInput.style.display = "none";
+  view.appendChild(fileInput);
+
+  dropzone.addEventListener("click", () => fileInput.click());
+  fileInput.addEventListener("change", () => {
+    if (fileInput.files.length) uploadFiles(name, fileInput.files);
+    fileInput.value = "";
+  });
+
+  ["dragenter", "dragover"].forEach((evt) =>
+    dropzone.addEventListener(evt, (e) => {
+      e.preventDefault();
+      dropzone.classList.add("is-dragover");
+    })
+  );
+  ["dragleave", "drop"].forEach((evt) =>
+    dropzone.addEventListener(evt, (e) => {
+      e.preventDefault();
+      dropzone.classList.remove("is-dragover");
+    })
+  );
+  dropzone.addEventListener("drop", (e) => {
+    const files = e.dataTransfer.files;
+    if (files.length) uploadFiles(name, files);
+  });
+
+  const gridContainer = document.createElement("div");
+  gridContainer.id = "file-grid-container";
+  view.appendChild(gridContainer);
+
+  await loadFileGrid(name, gridContainer);
+}
+
+async function uploadFiles(projectName, fileList) {
+  const formData = new FormData();
+  let hasValid = false;
+  for (const file of fileList) {
+    const ext = "." + file.name.split(".").pop().toLowerCase();
+    if (ext === ".stl" || ext === ".3mf") {
+      formData.append("files", file);
+      hasValid = true;
+    }
+  }
+  if (!hasValid) {
+    showToast("Nur .stl und .3mf Dateien werden unterstützt.", true);
+    return;
+  }
+  try {
+    const result = await api(`/api/projects/${encodeURIComponent(projectName)}/upload`, {
+      method: "POST",
+      body: formData,
+    });
+    showToast(`${result.saved.length} Datei(en) hochgeladen`);
+    const container = document.getElementById("file-grid-container");
+    if (container) await loadFileGrid(projectName, container);
+  } catch (err) {
+    showToast("Upload fehlgeschlagen: " + err.message, true);
+  }
+}
+
+async function loadFileGrid(projectName, container) {
+  disposeViewers();
+  container.innerHTML = "";
+
+  let files = [];
+  try {
+    files = await api(`/api/projects/${encodeURIComponent(projectName)}/files`);
+  } catch (err) {
+    showToast("Dateien konnten nicht geladen werden: " + err.message, true);
+    return;
+  }
+
+  if (!files.length) {
+    const empty = document.createElement("div");
+    empty.className = "empty-state";
+    empty.textContent = "Noch keine Dateien in diesem Projekt.";
+    container.appendChild(empty);
+    return;
+  }
+
+  const grid = document.createElement("div");
+  grid.className = "file-grid";
+  container.appendChild(grid);
+
+  const tpl = document.getElementById("tpl-file-card");
+  for (const file of files) {
+    const card = tpl.content.firstElementChild.cloneNode(true);
+    card.querySelector(".file-card-name").textContent = file.name;
+    card.querySelector(".file-card-meta").textContent =
+      `${file.type.toUpperCase()} · ${formatSize(file.size)}`;
+
+    card.querySelector(".file-card-delete").addEventListener("click", async (e) => {
+      e.stopPropagation();
+      if (!confirm(`"${file.name}" löschen?`)) return;
+      try {
+        await api(
+          `/api/projects/${encodeURIComponent(projectName)}/files/${encodeURIComponent(file.name)}`,
+          { method: "DELETE" }
+        );
+        await loadFileGrid(projectName, container);
+      } catch (err) {
+        showToast("Löschen fehlgeschlagen: " + err.message, true);
+      }
+    });
+
+    grid.appendChild(card);
+    const canvasHost = card.querySelector(".file-card-canvas");
+    initViewer(canvasHost, `/api/projects/${encodeURIComponent(projectName)}/files/${encodeURIComponent(file.name)}`, file.type);
+  }
+}
+
+// ---------- Three.js viewer ----------
+
+function initViewer(host, url, type) {
+  const width = host.clientWidth || 260;
+  const height = host.clientHeight || 195;
+
+  const scene = new THREE.Scene();
+  scene.background = new THREE.Color(0x20252b);
+
+  const camera = new THREE.PerspectiveCamera(45, width / height, 0.1, 5000);
+
+  const renderer = new THREE.WebGLRenderer({ antialias: true });
+  renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
+  renderer.setSize(width, height);
+  host.appendChild(renderer.domElement);
+
+  const ambient = new THREE.AmbientLight(0xffffff, 0.6);
+  scene.add(ambient);
+  const key = new THREE.DirectionalLight(0xffffff, 0.9);
+  key.position.set(1, 1.5, 1);
+  scene.add(key);
+  const fill = new THREE.DirectionalLight(0xffffff, 0.4);
+  fill.position.set(-1, -0.5, -1);
+  scene.add(fill);
+
+  const controls = new OrbitControls(camera, renderer.domElement);
+  controls.enableDamping = true;
+  controls.dampingFactor = 0.08;
+
+  let frameId;
+  const animate = () => {
+    frameId = requestAnimationFrame(animate);
+    controls.update();
+    renderer.render(scene, camera);
+  };
+  animate();
+
+  const viewer = { host, renderer, scene, camera, controls, frameId: () => frameId };
+  activeViewers.push(viewer);
+
+  const resizeObserver = new ResizeObserver(() => {
+    const w = host.clientWidth;
+    const h = host.clientHeight;
+    if (w === 0 || h === 0) return;
+    camera.aspect = w / h;
+    camera.updateProjectionMatrix();
+    renderer.setSize(w, h);
+  });
+  resizeObserver.observe(host);
+  viewer.resizeObserver = resizeObserver;
+
+  const material = new THREE.MeshStandardMaterial({
+    color: 0xff6a35,
+    metalness: 0.15,
+    roughness: 0.55,
+  });
+
+  const fitAndAdd = (object3d) => {
+    const box = new THREE.Box3().setFromObject(object3d);
+    const size = new THREE.Vector3();
+    const center = new THREE.Vector3();
+    box.getSize(size);
+    box.getCenter(center);
+    object3d.position.sub(center);
+
+    const maxDim = Math.max(size.x, size.y, size.z) || 1;
+    const distance = maxDim * 2.2;
+    camera.position.set(distance, distance * 0.75, distance);
+    camera.near = maxDim / 100;
+    camera.far = maxDim * 100;
+    camera.updateProjectionMatrix();
+    controls.target.set(0, 0, 0);
+    controls.update();
+
+    scene.add(object3d);
+  };
+
+  if (type === "stl") {
+    stlLoader.load(
+      url,
+      (geometry) => {
+        geometry.computeVertexNormals();
+        const mesh = new THREE.Mesh(geometry, material);
+        fitAndAdd(mesh);
+      },
+      undefined,
+      () => showLoadError(host)
+    );
+  } else if (type === "3mf") {
+    mfLoader.load(
+      url,
+      (object) => {
+        fitAndAdd(object);
+      },
+      undefined,
+      () => showLoadError(host)
+    );
+  }
+}
+
+function showLoadError(host) {
+  const msg = document.createElement("div");
+  msg.style.cssText =
+    "position:absolute;inset:0;display:flex;align-items:center;justify-content:center;color:#8a929b;font-size:12px;padding:12px;text-align:center;";
+  msg.textContent = "Vorschau konnte nicht geladen werden";
+  host.style.position = "relative";
+  host.appendChild(msg);
+}
+
+function disposeViewers() {
+  while (activeViewers.length) {
+    const v = activeViewers.pop();
+    cancelAnimationFrame(v.frameId());
+    v.resizeObserver.disconnect();
+    v.controls.dispose();
+    v.renderer.dispose();
+    v.scene.traverse((obj) => {
+      if (obj.geometry) obj.geometry.dispose();
+      if (obj.material) {
+        if (Array.isArray(obj.material)) obj.material.forEach((m) => m.dispose());
+        else obj.material.dispose();
+      }
+    });
+  }
+}
+
+// ---------- Init ----------
+
+renderDashboard();
diff --git a/static/index.html b/static/index.html
new file mode 100644
index 0000000..ba912df
--- /dev/null
+++ b/static/index.html
@@ -0,0 +1,56 @@
+<!doctype html>
+<html lang="de">
+<head>
+  <meta charset="utf-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1" />
+  <title>3D Project Manager</title>
+  <link rel="stylesheet" href="/style.css" />
+  <script type="importmap">
+    {
+      "imports": {
+        "three": "https://unpkg.com/three@0.160.0/build/three.module.js",
+        "three/addons/": "https://unpkg.com/three@0.160.0/examples/jsm/"
+      }
+    }
+  </script>
+</head>
+<body>
+  <header class="topbar">
+    <div class="topbar-inner">
+      <a href="#" class="wordmark" id="home-link">
+        <span class="wordmark-mark">◇</span> 3D Project Manager
+      </a>
+      <nav class="crumbs" id="crumbs"></nav>
+    </div>
+  </header>
+
+  <main id="view" class="view"></main>
+
+  <template id="tpl-project-card">
+    <button class="project-card" type="button">
+      <span class="project-card-name"></span>
+      <span class="project-card-meta"></span>
+    </button>
+  </template>
+
+  <template id="tpl-new-project-card">
+    <button class="project-card project-card--new" type="button">
+      <span class="new-icon">+</span>
+      <span class="project-card-name">Neues Projekt</span>
+    </button>
+  </template>
+
+  <template id="tpl-file-card">
+    <div class="file-card">
+      <div class="file-card-canvas"></div>
+      <div class="file-card-info">
+        <span class="file-card-name"></span>
+        <span class="file-card-meta"></span>
+      </div>
+      <button class="file-card-delete" type="button" title="Datei löschen">×</button>
+    </div>
+  </template>
+
+  <script type="module" src="/app.js"></script>
+</body>
+</html>
diff --git a/static/style.css b/static/style.css
new file mode 100644
index 0000000..1993038
--- /dev/null
+++ b/static/style.css
@@ -0,0 +1,360 @@
+:root {
+  --bg: #14171a;
+  --panel: #1b1f23;
+  --panel-alt: #20252b;
+  --border: #2a2f36;
+  --border-strong: #3a4048;
+  --text: #e8eaed;
+  --text-muted: #8a929b;
+  --accent: #ff6a35;
+  --accent-dim: #7a3a22;
+  --danger: #e0605c;
+  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
+  --font-mono: "SF Mono", "Cascadia Code", Consolas, "Roboto Mono", monospace;
+  --radius: 6px;
+}
+
+* { box-sizing: border-box; }
+
+html, body {
+  margin: 0;
+  height: 100%;
+  background: var(--bg);
+  color: var(--text);
+  font-family: var(--font-sans);
+}
+
+a { color: inherit; text-decoration: none; }
+
+button {
+  font-family: inherit;
+  cursor: pointer;
+}
+
+/* Topbar */
+
+.topbar {
+  border-bottom: 1px solid var(--border);
+  background: var(--bg);
+  position: sticky;
+  top: 0;
+  z-index: 10;
+}
+
+.topbar-inner {
+  max-width: 1200px;
+  margin: 0 auto;
+  padding: 18px 28px;
+  display: flex;
+  align-items: baseline;
+  gap: 14px;
+}
+
+.wordmark {
+  font-size: 17px;
+  font-weight: 600;
+  letter-spacing: -0.01em;
+  color: var(--text);
+}
+
+.wordmark-mark {
+  color: var(--accent);
+  margin-right: 2px;
+}
+
+.crumbs {
+  color: var(--text-muted);
+  font-size: 14px;
+}
+
+.crumbs a {
+  color: var(--text-muted);
+  border-bottom: 1px solid transparent;
+}
+
+.crumbs a:hover {
+  color: var(--text);
+  border-bottom-color: var(--border-strong);
+}
+
+.crumbs .sep {
+  margin: 0 8px;
+  color: var(--border-strong);
+}
+
+.crumbs .current {
+  color: var(--text);
+}
+
+/* Layout */
+
+.view {
+  max-width: 1200px;
+  margin: 0 auto;
+  padding: 32px 28px 80px;
+}
+
+.view-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 24px;
+  gap: 16px;
+}
+
+.view-title {
+  font-size: 22px;
+  font-weight: 600;
+  letter-spacing: -0.01em;
+  margin: 0;
+}
+
+.view-subtitle {
+  color: var(--text-muted);
+  font-size: 14px;
+  margin-top: 4px;
+}
+
+.btn {
+  border: 1px solid var(--border-strong);
+  background: transparent;
+  color: var(--text);
+  border-radius: var(--radius);
+  padding: 9px 16px;
+  font-size: 14px;
+  font-weight: 500;
+  transition: border-color 0.15s ease, background 0.15s ease;
+}
+
+.btn:hover {
+  border-color: var(--accent);
+}
+
+.btn-danger {
+  border-color: var(--border-strong);
+  color: var(--danger);
+}
+
+.btn-danger:hover {
+  border-color: var(--danger);
+}
+
+/* Project grid */
+
+.project-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
+  gap: 14px;
+}
+
+.project-card {
+  border: 1px solid var(--border);
+  background: var(--panel);
+  border-radius: var(--radius);
+  padding: 20px 18px;
+  text-align: left;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  min-height: 84px;
+  transition: border-color 0.15s ease, transform 0.1s ease;
+}
+
+.project-card:hover {
+  border-color: var(--border-strong);
+}
+
+.project-card-name {
+  font-size: 15px;
+  font-weight: 600;
+  color: var(--text);
+  word-break: break-word;
+}
+
+.project-card-meta {
+  font-size: 13px;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+.project-card--new {
+  border-style: dashed;
+  align-items: flex-start;
+  justify-content: center;
+  color: var(--text-muted);
+}
+
+.project-card--new:hover {
+  border-color: var(--accent);
+  color: var(--accent);
+}
+
+.new-icon {
+  font-size: 22px;
+  line-height: 1;
+  margin-bottom: 4px;
+}
+
+.empty-state {
+  border: 1px dashed var(--border);
+  border-radius: var(--radius);
+  padding: 48px 24px;
+  text-align: center;
+  color: var(--text-muted);
+  font-size: 14px;
+}
+
+/* Inline new-project form */
+
+.new-project-form {
+  border: 1px solid var(--border-strong);
+  background: var(--panel);
+  border-radius: var(--radius);
+  padding: 20px;
+  display: flex;
+  gap: 10px;
+  align-items: center;
+  margin-bottom: 20px;
+}
+
+.new-project-form input[type="text"] {
+  flex: 1;
+  background: var(--panel-alt);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  color: var(--text);
+  padding: 9px 12px;
+  font-size: 14px;
+  font-family: inherit;
+}
+
+.new-project-form input[type="text"]:focus {
+  outline: none;
+  border-color: var(--accent);
+}
+
+/* Dropzone */
+
+.dropzone {
+  border: 1px dashed var(--border-strong);
+  border-radius: var(--radius);
+  padding: 22px;
+  text-align: center;
+  color: var(--text-muted);
+  font-size: 14px;
+  margin-bottom: 24px;
+  transition: border-color 0.15s ease, color 0.15s ease, background 0.15s ease;
+}
+
+.dropzone strong {
+  color: var(--text);
+  font-weight: 500;
+}
+
+.dropzone.is-dragover {
+  border-color: var(--accent);
+  color: var(--text);
+  background: rgba(255, 106, 53, 0.06);
+}
+
+/* File grid */
+
+.file-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
+  gap: 16px;
+}
+
+.file-card {
+  border: 1px solid var(--border);
+  background: var(--panel);
+  border-radius: var(--radius);
+  overflow: hidden;
+  position: relative;
+  animation: fade-in 0.25s ease;
+}
+
+@keyframes fade-in {
+  from { opacity: 0; transform: translateY(4px); }
+  to { opacity: 1; transform: translateY(0); }
+}
+
+.file-card-canvas {
+  width: 100%;
+  aspect-ratio: 4 / 3;
+  background: var(--panel-alt);
+}
+
+.file-card-canvas canvas {
+  display: block;
+  width: 100%;
+  height: 100%;
+}
+
+.file-card-info {
+  padding: 12px 14px;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  border-top: 1px solid var(--border);
+}
+
+.file-card-name {
+  font-family: var(--font-mono);
+  font-size: 13px;
+  color: var(--text);
+  word-break: break-all;
+}
+
+.file-card-meta {
+  font-family: var(--font-mono);
+  font-size: 12px;
+  color: var(--text-muted);
+}
+
+.file-card-delete {
+  position: absolute;
+  top: 8px;
+  right: 8px;
+  width: 24px;
+  height: 24px;
+  border-radius: 50%;
+  border: 1px solid var(--border-strong);
+  background: rgba(20, 23, 26, 0.85);
+  color: var(--text-muted);
+  font-size: 15px;
+  line-height: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  opacity: 0;
+  transition: opacity 0.15s ease, color 0.15s ease, border-color 0.15s ease;
+}
+
+.file-card:hover .file-card-delete {
+  opacity: 1;
+}
+
+.file-card-delete:hover {
+  color: var(--danger);
+  border-color: var(--danger);
+}
+
+.toast {
+  position: fixed;
+  bottom: 24px;
+  left: 50%;
+  transform: translateX(-50%);
+  background: var(--panel-alt);
+  border: 1px solid var(--border-strong);
+  border-radius: var(--radius);
+  padding: 10px 18px;
+  font-size: 13px;
+  color: var(--text);
+  z-index: 50;
+}
+
+.toast.toast--error {
+  border-color: var(--danger);
+  color: var(--danger);
+}