diff --git a/app/demo/index.html b/app/demo/index.html
index f3da360..2178436 100644
--- a/app/demo/index.html
+++ b/app/demo/index.html
@@ -490,8 +490,12 @@ function createScene(container, dataset) {
     trajectories: null,
     numFrames: 0,
     snapshotMs: 1000 / 12,
-    // random phase so the three scenes don't loop in lockstep
-    cycleStartMs: performance.now() - Math.random() * 2000,
+    // holdMs pads the end of each cycle at rest, so the pulse actually
+    // lands (otherwise frame-0-as-rest is zero-duration and never visible).
+    holdMs: 200,
+    // shared reference so all scenes stay in lockstep; applyF() sets this
+    // to the same value across scenes on every n-frames toggle.
+    cycleStartMs: 0,
   };
 }
 
@@ -515,7 +519,6 @@ function buildTrajectories(s, numFrames) {
   }
   s.trajectories = buf;
   s.numFrames = numFrames;
-  s.cycleStartMs = performance.now() - Math.random() * s.snapshotMs * numFrames;
 }
 
 function sizeScene(s) {
@@ -630,9 +633,11 @@ async function main() {
   const fInputs = document.querySelectorAll('input[name="f"]');
   function applyF(n) {
     numFrames = n;
+    // Shared start time keeps all three scenes in lockstep.
+    const start = performance.now();
     for (const s of scenes) {
       s.numFrames = n;
-      s.cycleStartMs = performance.now() - Math.random() * s.snapshotMs * n;
+      s.cycleStartMs = start;
     }
   }
   fInputs.forEach(input => {
@@ -691,14 +696,9 @@ async function main() {
     for (const s of scenes) {
       const N = s.numFrames;
       const n = s.basePositions.length;
-      const cycleMs = N * s.snapshotMs;
+      const walkMs = N * s.snapshotMs;
+      const cycleMs = walkMs + s.holdMs;
       const elapsed = ((now - s.cycleStartMs) % cycleMs + cycleMs) % cycleMs;
-      const frameF = elapsed / s.snapshotMs;
-      const frameIdx = Math.floor(frameF);
-      const interpT = frameF - frameIdx;
-      const nextIdx = (frameIdx + 1) % N;
-      const aOff = frameIdx * n;
-      const bOff = nextIdx * n;
 
       const total = n / 3;
       const drawCount = s.geometry.drawRange.count;
@@ -706,13 +706,25 @@ async function main() {
       const limit = visibleN * 3;
       const pos = s.geometry.attributes.position.array;
       const base = s.basePositions;
-      const tr = s.trajectories;
-      // Jitter is applied in normalized space so σ means the same thing
-      // across datasets — independent of the raw feature magnitudes.
-      const scale = jitterScale;
-      const u = 1 - interpT;
-      for (let i = 0; i < limit; i++) {
-        pos[i] = base[i] + (tr[aOff + i] * u + tr[bOff + i] * interpT) * scale;
+
+      if (elapsed >= walkMs) {
+        // Hold zone: snap-back has landed, sit at rest until next cycle.
+        for (let i = 0; i < limit; i++) pos[i] = base[i];
+      } else {
+        const frameF = elapsed / s.snapshotMs;
+        const frameIdx = Math.floor(frameF);
+        const interpT = frameF - frameIdx;
+        const nextIdx = (frameIdx + 1) % N;
+        const aOff = frameIdx * n;
+        const bOff = nextIdx * n;
+        const tr = s.trajectories;
+        // Jitter is applied in normalized space so σ means the same thing
+        // across datasets — independent of the raw feature magnitudes.
+        const scale = jitterScale;
+        const u = 1 - interpT;
+        for (let i = 0; i < limit; i++) {
+          pos[i] = base[i] + (tr[aOff + i] * u + tr[bOff + i] * interpT) * scale;
+        }
       }
       s.geometry.attributes.position.needsUpdate = true;