diff --git a/.github/workflows/pages.yml b/.github/workflows/pages.yml
index ff967ec..0e7a189 100644
--- a/.github/workflows/pages.yml
+++ b/.github/workflows/pages.yml
@@ -22,12 +22,27 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
       - uses: actions/checkout@v4
+        with:
+          lfs: true
+      - name: Install ffmpeg (no longer preinstalled on ubuntu-latest runners)
+        run: sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends ffmpeg
       - name: Stage site (docs + videos + volumes referenced by the site)
         run: |
           mkdir -p site/videos site/img
-          cp assets/videos/*.mp4 site/videos/
           cp docs/algorithm.html site/ 2>/dev/null || true
           cp docs/images/example-run/*.png site/img/
+          # Committed videos are mp4v (MPEG-4 Part 2, ADR 0004), which Chrome/
+          # Firefox/Edge refuse to play in <video>. Re-encode to H.264 for the
+          # site only; the repo's assets/videos/*.mp4 stay mp4v.
+          ffmpeg -v error -y -i assets/videos/lecturer_example.mp4 \
+            -c:v libx264 -pix_fmt yuv420p -movflags +faststart \
+            site/videos/lecturer_example.mp4
+          ffmpeg -v error -y -i assets/videos/head.mp4 \
+            -c:v libx264 -pix_fmt yuv420p -movflags +faststart \
+            site/videos/head.mp4
+          ffmpeg -v error -y -i assets/videos/onion.mp4 \
+            -c:v libx264 -pix_fmt yuv420p -movflags +faststart \
+            site/videos/onion.mp4
       - uses: actions/configure-pages@v5
       - uses: actions/upload-pages-artifact@v3
         with:
diff --git a/README.md b/README.md
index a3d1149..ecb7ca3 100644
--- a/README.md
+++ b/README.md
@@ -23,8 +23,8 @@ A plane arrives as 3 or 4 points in a CSV row:
 
 | Points | Geometry | Validity rule (with `EPS = 0.001`) |
 |---:|---|---|
-| 3 | isosceles triangle `(a, b, c)` | `|dist(a,b) − dist(a,c)| < EPS` |
-| 4 | isosceles trapezoid `(a1, a2, b, c)` | `|dist(a1,b) − dist(a2,c)| < EPS`, `dist(a1,a2) ≤ dist(b,c)`, both legs on one plane |
+| 3 | isosceles triangle `(a, b, c)` | `\|dist(a,b) − dist(a,c)\| < EPS` |
+| 4 | isosceles trapezoid `(a1, a2, b, c)` | `\|dist(a1,b) − dist(a2,c)\| < EPS`, `dist(a1,a2) ≤ dist(b,c)`, both legs on one plane |
 
 An invalid row raises internally and becomes a **black error frame** with a red
 banner naming the row and the failing rule; the remaining rows still render, so
@@ -78,6 +78,8 @@ python Ex0.py assets/nrrd/MRHead_1.nrrd assets/csv/lecturer_example.csv out.mp4
 ```
 row 1: ok (triangle)
 row 2: ok (trapezoid)
+row 3: |dist(a,b) − dist(a,c)| = 20.5284 ≥ EPS = 0.001 (dist(a,b) = 497.393, dist(a,c) = 476.865)
+row 4: |dist(a1,b) − dist(a2,c)| = 100 ≥ EPS = 0.001 (dist(a1,b) = 300, dist(a2,c) = 400)
 wrote 4 frames (500x448, mp4v @30 fps) to 'out.mp4' (2 error row(s))
 ```
 
diff --git a/site/index.html b/site/index.html
index a1dd93f..6ee2ba7 100644
--- a/site/index.html
+++ b/site/index.html
@@ -166,7 +166,7 @@ <h2>Demo videos</h2>
   <!-- ============ quickstart ============ -->
   <section id="quickstart">
     <h2>Quickstart</h2>
-    <p class="section-sub">Python ≥ 3.10 (exercised on 3.12). Everything is pip-installable.</p>
+    <p class="section-sub">Python ≥ 3.12 (numpy 2.5 requires it). Everything is pip-installable.</p>
     <pre class="term">
 <span class="c"># clone + set up</span>
 <span class="p">$</span> git clone https://github.com/ofeq-dev/plane-projection.git