diff --git a/frontend/js/labs/opticsbench.js b/frontend/js/labs/opticsbench.js
index 21a0b4e..e072c2b 100644
--- a/frontend/js/labs/opticsbench.js
+++ b/frontend/js/labs/opticsbench.js
@@ -2545,7 +2545,7 @@ class BenchSim {
     this._drag = null;
     this._nextId = 1;
     // source: object arrow by default. `ang` (deg) aims point/single/laser/parallel.
-    this.source = { kind: 'object', xf: 0.07, h: 70, spread: 0.32, rays: 9, ang: 0 };
+    this.source = { kind: 'object', xf: 0.07, yf: 0, h: 70, spread: 0.32, rays: 9, ang: 0 };
     // elements along the bench, positioned by x-fraction; centred on the axis
     this.elements = [
       this._mk('lens',   { xf: 0.40, f: 130, ap: 95 }),
@@ -2612,10 +2612,11 @@ class BenchSim {
   /* ── geometry helpers ── */
   _ex(el) { return el.xf * this.W; }
   _ay() { return this.H / 2; }
+  _sy() { return this._ay() + (this.source.yf || 0) * (this.H / 2 - 14); } // source y (vertical position)
 
   /* Emit the initial rays from the source. */
   _emitRays() {
-    const ay = this._ay();
+    const ay = this._sy();          // emission height respects the source vertical position
     const sx = this.source.xf * this.W;
     const rays = [];
     // white light → one sub-ray per spectral sample (they coincide until a prism disperses them)
@@ -2795,7 +2796,9 @@ class BenchSim {
     this._drawScreenHits(ctx, rays);
 
     if (typeof _drawOBFXLayer === 'function') {
-      _drawOBFXLayer(ctx, 'freebuild', { srcX: this.source.xf * W, srcY: ay - (this.source.h || 0) });
+      // FX anchored at the actual source point (only the object arrow has a raised tip)
+      const fxY = this._sy() - (this.source.kind === 'object' ? this.source.h : 0);
+      _drawOBFXLayer(ctx, 'freebuild', { srcX: this.source.xf * W, srcY: fxY });
     }
   }
 
@@ -2819,7 +2822,8 @@ class BenchSim {
     ctx.restore();
   }
 
-  _drawSource(ctx, ay) {
+  _drawSource(ctx, _ayIgnored) {
+    const ay = this._sy();          // draw at the source vertical position
     const sx = this.source.xf * this.W;
     const aim = (this.source.ang || 0) * Math.PI / 180;
     ctx.save();
@@ -2938,11 +2942,12 @@ class BenchSim {
     };
     const hit = (mx, my) => {
       const ay = this._ay();
+      // source first (it can sit off-axis), grab around its actual vertical position
+      const sx = this.source.xf * this.W, sy = this._sy();
+      if (Math.abs(mx - sx) < 16 && Math.abs(my - sy) < 70) return { kind: 'src' };
       for (const el of this.elements) {
         if (Math.abs(mx - this._ex(el)) < 14 && Math.abs(my - ay) < 120) return { kind: 'el', id: el.id };
       }
-      const sx = this.source.xf * this.W;
-      if (Math.abs(mx - sx) < 16 && Math.abs(my - ay) < 120) return { kind: 'src' };
       return null;
     };
     on(cv, 'pointerdown', e => {
@@ -2957,10 +2962,14 @@ class BenchSim {
     });
     on(cv, 'pointermove', e => {
       if (!this._drag) { const { mx, my } = pos(e); cv.style.cursor = hit(mx, my) ? 'grab' : 'default'; return; }
-      const { mx } = pos(e);
+      const { mx, my } = pos(e);
       const xf = Math.max(0.02, Math.min(0.98, mx / this.W));
-      if (this._drag.kind === 'src') this.source.xf = xf;
-      else { const el = this.elements.find(x => x.id === this._drag.id); if (el) el.xf = xf; }
+      if (this._drag.kind === 'src') {
+        this.source.xf = xf;
+        // vertical drag too → move the source up/down off the axis
+        const yf = (my - this._ay()) / (this.H / 2 - 14);
+        this.source.yf = Math.max(-0.95, Math.min(0.95, yf));
+      } else { const el = this.elements.find(x => x.id === this._drag.id); if (el) el.xf = xf; }
       this._redraw();          // position drag → redraw canvas, keep inspector intact
     });
     on(cv, 'pointerup', e => { this._drag = null; try { cv.releasePointerCapture(e.pointerId); } catch (_) {} });
@@ -4444,9 +4453,9 @@ function _benchPropsHTML() {
     let h = '<div class="gp-section-title" style="margin:4px 0 6px">Источник</div>';
     h += _benchBtnRow(['object:Предмет', 'point:Точка', 'parallel:Параллель', 'single:Луч', 'laser:Лазер'],
       k => s.kind === k, k => "benchSourceKind('" + k + "')");
-    if (s.kind === 'object') h += _benchCtl('Высота', 0, 'h', 20, 120, 2, s.h, true);
+    h += _benchCtl('Положение ↕', 0, 'yf', -0.9, 0.9, 0.02, +(s.yf || 0).toFixed(2), true);  // vertical position (any kind)
+    if (s.kind === 'object') h += _benchCtl('Размер стрелки', 0, 'h', 20, 120, 2, s.h, true);
     if (s.kind === 'point') h += _benchCtl('Раствор', 0, 'spread', 0.1, 0.6, 0.02, s.spread, true);
-    if (s.kind !== 'object' && s.kind !== 'parallel') {} // no spread for single/laser
     if (s.kind !== 'object') h += _benchCtl('Угол°', 0, 'ang', -60, 60, 1, s.ang || 0, true);
     return h;
   }
diff --git a/frontend/lab.html b/frontend/lab.html
index 986c930..2f20142 100644
--- a/frontend/lab.html
+++ b/frontend/lab.html
@@ -4847,7 +4847,7 @@
 <script src="/js/labs/graphtransform.js"></script>
 <script src="/js/labs/pendulum.js"></script>
 <script src="/js/labs/equilibrium.js"></script>
-    <script src="/js/labs/opticsbench.js?v=7"></script>
+    <script src="/js/labs/opticsbench.js?v=8"></script>
 <script src="/js/labs/isoprocess.js"></script>
 <script src="/js/labs/titration.js"></script>
 <script src="/js/labs/probability.js"></script>