diff --git a/csp/sync.csp b/csp/sync.csp
index b12d529..7eb48c2 100644
--- a/csp/sync.csp
+++ b/csp/sync.csp
@@ -1,12 +1,19 @@
 N = 3
-channel input, up, save:{0..N-1}
+channel input, render, up, down, save:{0..N-1}
 
 apply(state, patch) = (state + patch) % N
 diff(state1, state2) = (state2 - state1) % N
 
-CLIENT(state, shadow) = input?new_state -> up!diff(shadow, new_state) -> CLIENT(new_state, shadow)
+CLIENT(state, shadow) = 
+   input?new_state -> up!diff(shadow, new_state) -> CLIENT(new_state, shadow)
+[] down?patch -> if patch != 0 
+     then render!apply(state, patch) -> CLIENT(apply(state, patch), apply(shadow, patch))
+     else CLIENT(state, state)
+
 SERVER(state, shadow) = 
-  up?patch -> save!apply(state, patch) -> SERVER(apply(state, patch), apply(shadow, patch))
+  up?patch -> save!apply(state, patch) -> down!diff(apply(shadow, patch), apply(state, patch))
+  -> SERVER(apply(state, patch), apply(shadow, patch))
+
 SYSTEM = CLIENT(0, 0) ||| SERVER(0, 0)
 
 assert SYSTEM :[deadlock free [F]]
\ No newline at end of file