diff --git a/context/plan.md b/context/plan.md
index 64eae032..2abf1f68 100644
--- a/context/plan.md
+++ b/context/plan.md
@@ -175,7 +175,7 @@ Generate the GIF by running `nix develop --command vhs docs/demo.tape`. Iterate
 
 Asciinema produces `.cast` files that the asciinema-player JS widget can replay in a browser, with selectable text and pixel-perfect terminal rendering. These will be embedded in the GitHub Pages landing page in Phase 4.
 
-Before recording, set the terminal to exactly 100 columns by 30 rows: `stty cols 100 rows 30` (or resize the terminal window manually if `stty` doesn't take). This matters because the asciinema player renders at the recorded dimensions and a wrong size will look broken on the landing page.
+Before recording, set the terminal to match what `docs/index.html` declares. That is **120 columns by 37 rows** today, not the 100x30 this plan originally said: the casts that were actually recorded are 120x37, and the landing page follows the recordings rather than the other way round, because a 30-row player clips the bottom seven rows of a 37-row cast — which is where the tile bar and the status line are. `stty cols 120 rows 37` (or resize the window manually if `stty` doesn't take). Whichever geometry is used, the two must agree: the player renders at the size it is told and a mismatch looks broken. If a re-recording changes it, change `cols`/`rows` in `docs/index.html` in the same commit (improvise-2oxt).
 
 Record four casts under `docs/casts/`:
 
@@ -235,11 +235,15 @@ Vanilla HTML, single file, under 200 lines. No framework, no build step. Dark ba
 
 Section structure: title and one-line tagline → "Reassign axes on the fly" with the pivot cast → "Drill into aggregated cells" with the drill cast → "Formulas over dimensions" with the formulas cast → "Import a CSV" with the import cast → "Get it" with the install commands and a GitHub link.
 
-Each cast should be embedded with `AsciinemaPlayer.create()` configured with `rows: 30, cols: 100, theme: 'monokai', autoPlay: false, loop: true`.
+Each cast should be embedded with `AsciinemaPlayer.create()` configured with `theme: 'monokai', autoPlay: false, loop: true`, and `cols`/`rows` set to the casts' own geometry — 120x37 as recorded, not the 100x30 this plan first specified. See 2.4.
 
 ### 4.2 Enable GitHub Pages
 
-In the GitHub repo settings, enable Pages with source set to the `main` branch and folder set to `/docs`. Verify the site is live at `https://<user>.github.io/improvise/` within a few minutes of pushing.
+**Not branch-and-folder.** Pages is served from the GitHub Actions artifact that `pages-build` / `pages-deploy` publish in `.github/workflows/ci.yml` (Settings → Pages → Source: GitHub Actions), and the tree is assembled by `web/assemble.sh`: `docs/index.html` and `docs/casts/` at the root, the browser app under `app/`.
+
+Setting the source to branch `main` / folder `/docs` instead would serve `docs/` raw. That used to fail loudly — there was no `docs/index.html`, so it was a 404 — and since improvise-e61 it fails **quietly**: the landing page renders perfectly and its "Run improvise in your browser" link 404s, because `app/` exists only in the assembled tree. A page that looks right with a dead front door is worse than a page that is missing.
+
+Verify the site is live at `https://<user>.github.io/improvise/` within a few minutes of pushing, and click through to the app rather than only loading the root.
 
 ---
 
diff --git a/docs/index.html b/docs/index.html
index 960356d6..acdaa0cd 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -95,6 +95,16 @@
         border-radius: 6px;
         overflow: hidden;
       }
+      /* A 120-column cast shrunk to a phone gives a ~5px font. Scroll it
+         sideways at a legible size instead of rendering it unreadable. */
+      @media (max-width: 900px) {
+        .player {
+          overflow-x: auto;
+        }
+        .player > * {
+          min-width: 880px;
+        }
+      }
       pre {
         background: var(--panel);
         border: 1px solid var(--rule);