docs: add docs/pong.gif demo to README

Record a 6-second gif of examples/pong.nes running in jsnes and
embed it alongside docs/platformer.gif and docs/war.gif as the
third project demo. The gif opens on Pong's title menu (CPU VS
CPU / 1 PLAYER / 2 PLAYERS) — warmup = 4 frames keeps the menu
as the thumbnail the way war's recording does, and then the
headless autopilot advances to gameplay partway through the
clip.

- docs/pong.gif committed (128 KB)
- README.md links it under the war demo
- scripts/pre-commit rebuilds it when examples/pong* or the
  recorder/harness change
- .github/workflows/ci.yml fails if the committed copy is stale
- CLAUDE.md and tests/emulator/record_gif.mjs reference the new
  gif in the "how to regenerate" sections

https://claude.ai/code/session_0134F5uwDEVTes2Ee9S7JeXy

.github/workflows/ci.yml

@@ -176,6 +176,19 @@ jobs:
             echo "::error file=docs/war.gif::committed docs/war.gif is stale; rerun \`node tests/emulator/record_gif.mjs war 360 2 docs/war.gif 4\` and commit the new gif"
             exit 1
           fi
+      - name: Verify docs/pong.gif is up to date
+        # Same contract as the platformer and war gifs: the README
+        # embeds docs/pong.gif as the third project demo. Pong's
+        # title screen (CPU VS CPU / 1 PLAYER / 2 PLAYERS menu) is
+        # the gif thumbnail, so warmup = 4 keeps it in frame before
+        # the autopilot advances to gameplay.
+        working-directory: tests/emulator
+        run: |
+          node record_gif.mjs pong 360 2 /tmp/pong.gif 4
+          if ! cmp -s ../../docs/pong.gif /tmp/pong.gif; then
+            echo "::error file=docs/pong.gif::committed docs/pong.gif is stale; rerun \`node tests/emulator/record_gif.mjs pong 360 2 docs/pong.gif 4\` and commit the new gif"
+            exit 1
+          fi
       - name: Upload actual + diff PNGs on failure
         if: failure()
         uses: actions/upload-artifact@v4

CLAUDE.md

@@ -22,28 +22,31 @@ re-derive the project conventions from scratch.
   tmp path and fails if the committed version differs, pointing at
   the exact `cargo run -- build examples/<name>.ne` to run. The
   pre-commit hook under `scripts/pre-commit` catches this locally.
-- **`docs/platformer.gif` and `docs/war.gif` are committed** and
-  embedded in the top-level README as the project demos. `gifenc` +
-  `jsnes` are deterministic, so each gif's bytes are a function of
-  the compiler, the runtime, the harness, and the underlying `.ne`
-  source(s). Any change to those that affects the first ~6 seconds
-  of observable gameplay must be followed by regenerating the
-  affected gif:
+- **`docs/platformer.gif`, `docs/war.gif`, and `docs/pong.gif` are
+  committed** and embedded in the top-level README as the project
+  demos. `gifenc` + `jsnes` are deterministic, so each gif's bytes
+  are a function of the compiler, the runtime, the harness, and
+  the underlying `.ne` source(s). Any change to those that affects
+  the first ~6 seconds of observable gameplay must be followed by
+  regenerating the affected gif:
 
   ```bash
   node tests/emulator/record_gif.mjs platformer 360 2 docs/platformer.gif
   node tests/emulator/record_gif.mjs war        360 2 docs/war.gif        4
+  node tests/emulator/record_gif.mjs pong       360 2 docs/pong.gif       4
   ```
 
-  (The trailing `4` on the war command is the warmup-frames
-  override — war's title menu is the gif thumbnail, so we don't
-  skip past it the way the platformer recording does.) Commit the
-  regenerated gif in the same change. CI's `emulator` job renders
-  fresh gifs and fails if either committed copy doesn't byte-match.
-  The pre-commit hook rebuilds whichever gif is affected when
-  `platformer.ne`, `platformer.nes`, any file under `examples/war/`,
-  `war.ne`, `war.nes`, `record_gif.mjs`, or `harness.html` is
-  staged (and `tests/emulator/node_modules` is installed).
+  (The trailing `4` on the war and pong commands is the
+  warmup-frames override — both open on a title menu that we want
+  as the gif thumbnail, so we don't skip past it the way the
+  platformer recording does.) Commit the regenerated gif in the
+  same change. CI's `emulator` job renders fresh gifs and fails if
+  any committed copy doesn't byte-match. The pre-commit hook
+  rebuilds whichever gif is affected when `platformer.ne`,
+  `platformer.nes`, any file under `examples/war/`, `war.ne`,
+  `war.nes`, any file under `examples/pong/`, `pong.ne`,
+  `pong.nes`, `record_gif.mjs`, or `harness.html` is staged (and
+  `tests/emulator/node_modules` is installed).
 - `docs/future-work.md` lists the remaining gaps. If you implement
   something from that file, update the doc in the same PR.
 

README.md

@@ -12,6 +12,10 @@ _Source: [`examples/platformer.ne`](examples/platformer.ne)_
 
 _Source: [`examples/war.ne`](examples/war.ne)_
 
+![Pong demo](docs/pong.gif)
+
+_Source: [`examples/pong.ne`](examples/pong.ne)_
+
 ## Quick Start
 
 ```bash

scripts/pre-commit

@@ -86,4 +86,9 @@ if [ $recorder_or_harness_changed -eq 1 ] || \
     check_gif war 4 || exit 1
 fi
 
+if [ $recorder_or_harness_changed -eq 1 ] || \
+   echo "$changed_files" | grep -qE '^examples/pong(\.(ne|nes)|/[^/]+\.ne)$'; then
+    check_gif pong 4 || exit 1
+fi
+
 echo "All pre-commit checks passed."

tests/emulator/record_gif.mjs

@@ -6,6 +6,7 @@
 // Examples:
 //     node record_gif.mjs platformer 360 2 docs/platformer.gif
 //     node record_gif.mjs war 360 2 docs/war.gif 4
+//     node record_gif.mjs pong 360 2 docs/pong.gif 4
 //
 // The recorder drives `harness.html` via puppeteer, collects one
 // canvas frame every `stride` NES frames for `frames` total, and
@@ -20,14 +21,15 @@
 // recording uses 4 instead because that demo opens on its menu and
 // we want the title screen to be the gif's thumbnail.
 //
-// IMPORTANT: `docs/platformer.gif` and `docs/war.gif` are committed
-// and embedded in the README. Any change to the compiler, the
-// runtime, the harness, or the underlying `.ne` source that alters
-// the gameplay you see in the first ~6 seconds of either demo must
-// be followed by
+// IMPORTANT: `docs/platformer.gif`, `docs/war.gif`, and
+// `docs/pong.gif` are committed and embedded in the README. Any
+// change to the compiler, the runtime, the harness, or the
+// underlying `.ne` source that alters the gameplay you see in the
+// first ~6 seconds of any of the three demos must be followed by
 //
 //     node tests/emulator/record_gif.mjs platformer 360 2 docs/platformer.gif
 //     node tests/emulator/record_gif.mjs war        360 2 docs/war.gif        4
+//     node tests/emulator/record_gif.mjs pong       360 2 docs/pong.gif       4
 //
 // committed alongside the source change. The CI `emulator` job
 // regenerates both gifs and fails if the committed copies are stale —