diff --git a/shell/README.md b/shell/README.md
index c1dee248..fabf16fa 100644
--- a/shell/README.md
+++ b/shell/README.md
@@ -6,3 +6,16 @@ Currently runs a tiny subset of Lisp. To build and run it from the top-level:
 ./translate shell/*.mu
 qemu-system-i386 disk.img
 ```
+
+You can type in expressions, hit `ctrl-s` to see their results, and hit `Tab`
+to focus on the `...` below and browse how the results were computed. [Here's
+a demo.](https://merveilles.town/@akkartik/105790894303047592) The bottom of
+the screen shows context-dependent keyboard shortcuts (there's no mouse in the
+Mu computer at the moment).
+
+*Known issues*
+
+* There's no way to save to disk.
+
+* Don't press keys too quickly (such as by holding down a key). The Mu
+  computer will crash (and often Qemu will segfault).