docs: add docs/war.gif demo to README

Captures the first ~6 s of examples/war.ne via the same
puppeteer + jsnes + gifenc pipeline that powers
docs/platformer.gif: title menu thumbnail, 52-card deal
animation, and a few rounds of CPU vs CPU play. Embedded
in the top-level README right under the platformer demo.

record_gif.mjs gains a 6th positional arg for the warmup
override (defaulting to the existing WARMUP env / 30) so
the war command can keep its title menu as the first frame
while platformer keeps skipping past its own title. The
CI emulator job and the pre-commit hook both rebuild the
gif into a tmp path and fail-with-fix-command if the
committed copy is stale; the war trigger covers war.ne,
war.nes, any examples/war/*.ne include, plus the recorder
and harness.

.github/workflows/ci.yml

@@ -161,6 +161,21 @@ jobs:
             echo "::error file=docs/platformer.gif::committed docs/platformer.gif is stale; rerun \`node tests/emulator/record_gif.mjs platformer 360 2 docs/platformer.gif\` and commit the new gif"
             exit 1
           fi
+      - name: Verify docs/war.gif is up to date
+        # Same contract as docs/platformer.gif: the README embeds
+        # docs/war.gif as the second project demo, gifenc + jsnes are
+        # deterministic, so any change to the compiler / runtime /
+        # harness / war source that affects the first ~6 seconds of
+        # the war.ne gameplay must be followed by regenerating the
+        # gif. The 5th positional arg (`4`) is the warmup; war's
+        # title menu is the gif thumbnail so we don't skip past it.
+        working-directory: tests/emulator
+        run: |
+          node record_gif.mjs war 360 2 /tmp/war.gif 4
+          if ! cmp -s ../../docs/war.gif /tmp/war.gif; then
+            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: Upload actual + diff PNGs on failure
         if: failure()
         uses: actions/upload-artifact@v4

CLAUDE.md

@@ -22,22 +22,28 @@ 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` is committed** and embedded in the
-  top-level README as the project demo. `gifenc` + `jsnes` are
-  deterministic, so the gif's bytes are a function of the compiler,
-  the runtime, the harness, and `examples/platformer.ne`. Any change
-  to those that affects the first ~6 seconds of observable platformer
-  gameplay must be followed by regenerating the gif:
+- **`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:
 
   ```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
   ```
 
-  and committing it in the same change. CI's `emulator` job renders
-  a fresh gif and fails if the committed one doesn't byte-match. The
-  pre-commit hook rebuilds the gif when `platformer.ne`, `platformer.nes`,
-  `record_gif.mjs`, or `harness.html` is staged (and `tests/emulator/node_modules`
-  is installed).
+  (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).
 - `docs/future-work.md` lists the remaining gaps. If you implement
   something from that file, update the doc in the same PR.
 

README.md

@@ -8,6 +8,10 @@ NEScript compiles `.ne` source files directly into playable iNES ROM files, with
 
 _Source: [`examples/platformer.ne`](examples/platformer.ne)_
 
+![War demo](docs/war.gif)
+
+_Source: [`examples/war.ne`](examples/war.ne)_
+
 ## Quick Start
 
 ```bash

scripts/pre-commit

@@ -39,26 +39,51 @@ if [ $stale -ne 0 ]; then
     exit 1
 fi
 
-# Only rebuild docs/platformer.gif when platformer.nes or the gif
-# recorder itself changed — the gif regeneration takes ~20s due to
-# puppeteer's cold start, so we don't want to pay it on every commit.
-# Skipped entirely if node_modules isn't installed in the emulator
-# harness; the CI `emulator` job is the authoritative check.
+# Only rebuild docs/{platformer,war}.gif when the underlying
+# example sources, the gif recorder, or the harness changed — gif
+# regeneration takes ~20s per gif due to puppeteer's cold start,
+# so we don't want to pay it on every commit. Skipped entirely if
+# node_modules isn't installed in the emulator harness; the CI
+# `emulator` job is the authoritative check.
+#
+# `examples/war.ne` pulls in `examples/war/*.ne` via include
+# directives, so any file under `examples/war/` is treated as a
+# trigger for rebuilding the war gif — the parser's preprocess
+# pass sees them as part of the same translation unit.
 changed_files=$(git diff --cached --name-only)
-if echo "$changed_files" | grep -qE '^(examples/platformer\.(ne|nes)|tests/emulator/record_gif\.mjs|tests/emulator/harness\.html)$'; then
-    if [ -d tests/emulator/node_modules ]; then
-        echo "  Rebuilding docs/platformer.gif (platformer.nes or recorder changed)..."
-        (cd tests/emulator && node record_gif.mjs platformer 360 2 /tmp/platformer-precheck.gif >/dev/null)
-        if ! cmp -s docs/platformer.gif /tmp/platformer-precheck.gif; then
-            echo "    STALE: docs/platformer.gif"
-            echo "           rerun: node tests/emulator/record_gif.mjs platformer 360 2 docs/platformer.gif"
-            rm -f /tmp/platformer-precheck.gif
-            exit 1
-        fi
-        rm -f /tmp/platformer-precheck.gif
-    else
-        echo "  (skipping gif freshness check — tests/emulator/node_modules not installed)"
+recorder_or_harness_changed=0
+if echo "$changed_files" | grep -qE '^tests/emulator/(record_gif\.mjs|harness\.html)$'; then
+    recorder_or_harness_changed=1
+fi
+
+check_gif() {
+    name=$1
+    args=$2  # extra args to record_gif.mjs (e.g. "4" for warmup)
+    if [ ! -d tests/emulator/node_modules ]; then
+        echo "  (skipping $name gif freshness check — tests/emulator/node_modules not installed)"
+        return 0
     fi
+    echo "  Rebuilding docs/$name.gif..."
+    # shellcheck disable=SC2086
+    (cd tests/emulator && node record_gif.mjs "$name" 360 2 /tmp/${name}-precheck.gif $args >/dev/null)
+    if ! cmp -s "docs/$name.gif" "/tmp/${name}-precheck.gif"; then
+        echo "    STALE: docs/$name.gif"
+        echo "           rerun: node tests/emulator/record_gif.mjs $name 360 2 docs/$name.gif $args"
+        rm -f "/tmp/${name}-precheck.gif"
+        return 1
+    fi
+    rm -f "/tmp/${name}-precheck.gif"
+    return 0
+}
+
+if [ $recorder_or_harness_changed -eq 1 ] || \
+   echo "$changed_files" | grep -qE '^examples/platformer\.(ne|nes)$'; then
+    check_gif platformer "" || exit 1
+fi
+
+if [ $recorder_or_harness_changed -eq 1 ] || \
+   echo "$changed_files" | grep -qE '^examples/war(\.(ne|nes)|/[^/]+\.ne)$'; then
+    check_gif war 4 || exit 1
 fi
 
 echo "All pre-commit checks passed."

tests/emulator/record_gif.mjs

@@ -1,10 +1,11 @@
 // Record a GIF of a .nes ROM running in jsnes.
 //
 // Usage:
-//     node record_gif.mjs <rom-name> [frames] [stride] [output.gif]
+//     node record_gif.mjs <rom-name> [frames] [stride] [output.gif] [warmup]
 //
-// Example:
+// Examples:
 //     node record_gif.mjs platformer 360 2 docs/platformer.gif
+//     node record_gif.mjs war 360 2 docs/war.gif 4
 //
 // The recorder drives `harness.html` via puppeteer, collects one
 // canvas frame every `stride` NES frames for `frames` total, and
@@ -13,15 +14,23 @@
 // other NES frame (NES runs at ~60 fps), which is the right
 // tradeoff between smoothness and file size for a README demo.
 //
-// IMPORTANT: `docs/platformer.gif` is committed and embedded in the
-// README. Any change to the compiler, the runtime, the harness, or
-// `examples/platformer.ne` that alters the gameplay you see in the
-// first ~6 seconds of the demo must be followed by
+// `warmup` is the number of NES frames to advance before the first
+// captured frame. The default of 30 skips past the reset stall and
+// the platformer's auto-Title→Play handoff at frame 20; the war
+// 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
 //
 //     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
 //
 // committed alongside the source change. The CI `emulator` job
-// regenerates the gif and fails if the committed copy is stale —
+// regenerates both gifs and fails if the committed copies are stale —
 // gifenc + jsnes are deterministic, so the freshly-rendered bytes
 // byte-match a valid commit. See `.github/workflows/ci.yml`.
 
@@ -66,11 +75,18 @@ await page.waitForFunction(
 
 await page.evaluate((b) => window.nesHarness.loadRomBase64(b), romB64);
 
-// Warm-up: skip past the reset stall and any title screen so the
-// first captured frame shows real gameplay. 30 frames at 60 fps
-// covers ~0.5 s which is enough for the platformer example's
-// Title → Playing auto-transition at frame 20.
-const warmupFrames = parseInt(process.env.WARMUP ?? "30", 10);
+// Warm-up: skip past the reset stall and (optionally) any title
+// screen so the first captured frame shows what we want as the
+// gif's thumbnail. 30 frames at 60 fps covers ~0.5 s which is
+// enough for the platformer example's Title → Playing auto-
+// transition at frame 20. The war recording overrides this with
+// `4` (positional arg below) so the title menu is the first frame.
+// Positional arg wins; `WARMUP=…` env var is honoured for ad-hoc
+// experimentation.
+const warmupFrames = parseInt(
+  process.argv[6] ?? process.env.WARMUP ?? "30",
+  10,
+);
 await page.evaluate((n) => window.nesHarness.runFrames(n), warmupFrames);
 
 console.log(