diff --git a/just/observable-test.fnl b/just/observable-test.fnl
index 011df31..47bbef8 100644
--- a/just/observable-test.fnl
+++ b/just/observable-test.fnl
@@ -45,11 +45,20 @@
 
 (let [s (observable.new {:foo {:bar 43}})]
   (var win false)
-  ;; observers live on subtrees, not individual nodes
-  (s:observe [:foo] #(set win true))
+  ;; observer  on leaf
+  (s:observe [:foo :bar] #(set win true))
   (s:update [:foo :bar] 42)
   (expect (and win)))
 
+(let [s (observable.new {:foo {:bar 43}})]
+  (var win false)
+  ;; observer  on subtree
+  (s:observe [:foo] #(set win true))
+  (s:update [:foo :bar] 42)
+  (expect (and true win)))
+
+
+
 (let [s (observable.new {:foo {:bar {:baz 43}}})]
   (var win 0)
   ;; observers on ancestor trees are called after child trees
diff --git a/just/observable.fnl b/just/observable.fnl
index eb3014f..701cd27 100644
--- a/just/observable.fnl
+++ b/just/observable.fnl
@@ -3,32 +3,40 @@
 (fn concat [dest src]
   (table.move dest 1 (# dest) (# src) src))
 
-(fn update [data self path value]
+(fn update [data path value vivify?]
   (let [[first & rest] path]
     (if (next rest)
-        (update (. data first) self rest value)
-        (tset data first value))
-    (if data._subscribers
-        (each [_ f (pairs data._subscribers)] (f)))))
-
-(fn get [data self path]
-  (let [[first & rest] path]
-    (if (not first) data
-        (next rest) (get (. data first) self rest)
-        (. data first))))
-
-(fn observe [data self path fun]
-  (let [el (get data self path)]
-    (when el
-      (if el._subscribers
-          (table.insert el._subscribers fun)
-          (tset el :_subscribers [fun])))))
+        (do
+          (if (and vivify? (not (. data first)))
+              (tset data first {}))
+          (update (. data first) rest value))
+        (tset data first value))))
 
 (fn new [data]
-  {
-   :observe (partial observe data)
-   :update (partial update data)
-   :get (partial get data)
-   })
+  (let [observers {}
+        key [:obs]]
+    (fn get [data path]
+      (let [[first & rest] path]
+        (if (not first) data
+            (next rest) (get (. data first) rest)
+            (. (or data {}) first))))
+
+    (fn publish [observers path]
+      (let [[first & rest] path
+            os (. (or observers {}) first)]
+        (if (and (next rest) (next os)) (publish os rest))
+        (match os
+          {key list} (each [_ f (pairs list)] (f)))))
+
+    (fn observe [observers path fun]
+      (let [el (get observers path)]
+        (if el
+            (table.insert (. el key) fun)
+            (update observers path {key [fun]} true))))
+    {
+     :observe #(observe observers $2 $3)
+     :update #(do (update data $2 $3) (publish observers $2))
+     :get #(get data $2)
+     }))
 
 {: new }