diff --git a/src/app/alignment-ui.ts b/src/app/alignment-ui.ts
new file mode 100644
index 0000000..e891ce2
--- /dev/null
+++ b/src/app/alignment-ui.ts
@@ -0,0 +1,117 @@
+import type { Vec2, Mat3, Alignment } from '../types';
+import { imageToMachine, alignmentFromOrigin } from '../geometry/transform';
+
+export interface AlignmentDeps {
+  panel: HTMLElement;
+  overlay: HTMLCanvasElement;
+  getAlignment: () => Alignment;
+  getHomography: () => Mat3 | null;
+  onChange: () => void;
+}
+
+/** Convert a mouse event to normalized [0,1] coords over the overlay canvas box. */
+function normFromEvent(overlay: HTMLCanvasElement, ev: MouseEvent): Vec2 {
+  const rect = overlay.getBoundingClientRect();
+  return [
+    (ev.clientX - rect.left) / rect.width,
+    (ev.clientY - rect.top) / rect.height,
+  ];
+}
+
+export function mountAlignment(deps: AlignmentDeps): void {
+  const { panel, overlay } = deps;
+  panel.innerHTML = `
+    <h2>Alignment</h2>
+    <div class="row">X <input id="al-x" type="number" step="1" /> Y <input id="al-y" type="number" step="1" /></div>
+    <div class="row">Rotation° <input id="al-rot" type="number" step="0.5" /></div>
+    <div class="row"><button id="al-origin">Set origin by clicking video</button></div>
+    <div class="row"><small>Or drag the toolpath to move; Shift-drag to rotate. Arrow keys nudge 1&nbsp;mm.</small></div>
+  `;
+
+  const xEl = panel.querySelector('#al-x') as HTMLInputElement;
+  const yEl = panel.querySelector('#al-y') as HTMLInputElement;
+  const rotEl = panel.querySelector('#al-rot') as HTMLInputElement;
+
+  const sync = () => {
+    const a = deps.getAlignment();
+    xEl.value = a.tx.toFixed(1);
+    yEl.value = a.ty.toFixed(1);
+    rotEl.value = ((a.rot * 180) / Math.PI).toFixed(1);
+  };
+  sync();
+
+  const commitNumeric = () => {
+    const a = deps.getAlignment();
+    a.tx = parseFloat(xEl.value) || 0;
+    a.ty = parseFloat(yEl.value) || 0;
+    a.rot = ((parseFloat(rotEl.value) || 0) * Math.PI) / 180;
+    deps.onChange();
+  };
+  for (const el of [xEl, yEl, rotEl]) el.addEventListener('change', commitNumeric);
+
+  // Click-to-set-origin
+  let armOrigin = false;
+  (panel.querySelector('#al-origin') as HTMLButtonElement).addEventListener('click', () => {
+    armOrigin = true;
+    overlay.classList.add('interactive');
+  });
+
+  // Drag to move / Shift-drag to rotate
+  let dragging = false;
+  let lastMachine: Vec2 | null = null;
+
+  overlay.addEventListener('mousedown', (ev) => {
+    const H = deps.getHomography();
+    if (!H) return;
+    if (armOrigin) {
+      const a = deps.getAlignment();
+      const m = imageToMachine(H, normFromEvent(overlay, ev));
+      Object.assign(a, alignmentFromOrigin(m, a.rot));
+      armOrigin = false;
+      overlay.classList.remove('interactive');
+      sync();
+      deps.onChange();
+      return;
+    }
+    dragging = true;
+    overlay.classList.add('interactive');
+    lastMachine = imageToMachine(H, normFromEvent(overlay, ev));
+  });
+
+  window.addEventListener('mousemove', (ev) => {
+    if (!dragging) return;
+    const H = deps.getHomography();
+    if (!H || !lastMachine) return;
+    const a = deps.getAlignment();
+    const cur = imageToMachine(H, normFromEvent(overlay, ev));
+    if (ev.shiftKey) {
+      // rotate about the work origin's current machine position (tx,ty)
+      const angle = (p: Vec2) => Math.atan2(p[1] - a.ty, p[0] - a.tx);
+      a.rot += angle(cur) - angle(lastMachine);
+    } else {
+      a.tx += cur[0] - lastMachine[0];
+      a.ty += cur[1] - lastMachine[1];
+    }
+    lastMachine = cur;
+    sync();
+    deps.onChange();
+  });
+
+  window.addEventListener('mouseup', () => {
+    dragging = false;
+    overlay.classList.remove('interactive');
+  });
+
+  window.addEventListener('keydown', (ev) => {
+    const a = deps.getAlignment();
+    const step = 1;
+    if (ev.key === 'ArrowLeft') a.tx -= step;
+    else if (ev.key === 'ArrowRight') a.tx += step;
+    else if (ev.key === 'ArrowUp') a.ty -= step;
+    else if (ev.key === 'ArrowDown') a.ty += step;
+    else return;
+    ev.preventDefault();
+    sync();
+    deps.onChange();
+  });
+}
diff --git a/src/main.ts b/src/main.ts
index 1fd429e..36f6f2c 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -4,6 +4,7 @@ import { createState } from './app/state';
 import { computeOverlayRect, syncOverlay } from './app/layout';
 import { drawOverlay, clearCanvas } from './render/renderer';
 import { mountCalibration } from './app/calibration-ui';
+import { mountAlignment } from './app/alignment-ui';
 import type { RenderStyle } from './types';
 
 const stage = document.getElementById('stage') as HTMLDivElement;
@@ -59,6 +60,14 @@ mountCalibration({
   },
 });
 
+mountAlignment({
+  panel: document.getElementById('align-panel') as HTMLElement,
+  overlay,
+  getAlignment: () => state.alignment,
+  getHomography: () => state.homography,
+  onChange: render,
+});
+
 async function boot(): Promise<void> {
   try {
     const cfg = await loadConfig('config.json');