diff --git a/README.md b/README.md
index 4ebca2d..9f1a99f 100644
--- a/README.md
+++ b/README.md
@@ -532,6 +532,9 @@ mindpalace/
 A: Yes — `--demo` boots a full 12-room fixture palace with zero auth and
 zero network. No token, no Ollama needed. It's also what CI runs.
 
+**Q: How do I see the FPS?**
+A: Press F4 to toggle the FPS overlay. The DEBUG line shows FPS, room/hall counts, and frustum-culled counts. When comparing performance, check the machine specification and see [PERFORMANCE.md](docs/PERFORMANCE.md).
+
 **Q: I don't write Java. Can I still contribute?**
 A: Yes — three lanes need no Java at all: add a [fixture room](FIRST_PR.md)
 (JSON + a few text files, 15 min), improve the docs (every stumble is a