diff --git a/src/experimental/todo.txt b/src/experimental/note.txt
similarity index 85%
rename from src/experimental/todo.txt
rename to src/experimental/note.txt
index c84df401..74d9ae8b 100644
--- a/src/experimental/todo.txt
+++ b/src/experimental/note.txt
@@ -9,6 +9,7 @@ Preview
 - sweep
 - util/has
 - util/dedup
+- util/bsearch for a sorted lt by z, y, x
 
 bugs:
 - util/sort: z not sorted
\ No newline at end of file