diff --git a/lib/csys/program.ex b/lib/csys/program.ex
index d16f9cc..85985c5 100644
--- a/lib/csys/program.ex
+++ b/lib/csys/program.ex
@@ -11,7 +11,7 @@ defmodule Scopes.CSys.Program do
 
   def prepare(prog, args) do
     state = %State{
-      value: args[:bias], 
+      value: args[:bias] || 0, 
       count: 0,
       stage: :initial, 
       prog: prog
@@ -45,7 +45,7 @@ defmodule Scopes.CSys.Program do
     {stages, transitions}
   end
 
-  def prepare_basic(args \\ [threshold: 0, bias: 0]) do
+  def prepare_basic(args \\ []) do
     prepare(basic_prog(args), args)
   end
 
@@ -59,13 +59,11 @@ defmodule Scopes.CSys.Program do
     basic(args)
   end
 
-  #def basic(msg, scope) do  # + proc_ops
-  def basic(args) do  # + proc_ops
+  def basic(args) do
     fn msg, scope ->
       case Shape.head(msg) do
-        [:csys, :data | _rest] -> process_data(msg, scope, args)
+        [:csys, :data | _rest] -> process_basic(msg, scope, args)
         #[:csys, :trigger | _rest] -> process_trigger(msg, scope)
-        [:csys, :set | _rest] -> set(msg, scope)
         [:csys, :connect | _rest] -> CSys.connect(msg, scope)
         [:csys, :create, :succ | _rest] -> create_succ(msg, scope)
         [:csys, :create, :pred | _rest] -> create_pred(msg, scope)
@@ -78,26 +76,20 @@ defmodule Scopes.CSys.Program do
 
   # message handlers // proc steps
 
-  def process_value(_msg, _scope, _ops) do
-    #proc ops: 
-    #reduce, (&(&1 + &2))
-    #trigger_cond,  (&(&1 > 0))
-    #out_op, (&(&1)) # (&(rem(&1 - 1, 5) + 1)
-    #output (&forward_or_notify)
-    #next_op, (const(0)) # (&max(&1 - 5, 0))
-  end
-
-  def process_data(msg, scope, args) do
-    data = Shape.data(msg)
-    state = CSys.state(scope)
-    value_n = state.value + data.value
+  def process_basic(msg, scope, args) do
     threshold = args[:threshold] || 0
     bias = args[:bias] || 0
-    Logger.info data: data.value, state: state.value, threshold: threshold
+    limit = args[:limit]
+    data = Shape.data(msg)
+    state = CSys.state(scope)
+    Logger.info data: data, state_value: state.value, threshold: threshold
+    value_n = state.value + data.value
     if value_n >= threshold do
-      msg = Shape.create(Shape.head(msg), data: %{data | value: value_n})
+      value_out = limit && rem(value_n - 1, limit) + limit || value_n
+      value_next = limit && max(value_n - limit, bias) || bias
+      msg = Shape.create(Shape.head(msg), data: %{data | value: value_out})
       CSys.forward(msg, scope) || CSys.notify(msg, scope)
-      state_n = if bias, do: %{state | value: bias}, else: state
+      state_n = %{state | value: value_next}
       CSys.update(put_elem(scope, 0, state_n))
     else
       state_n = %{state | value: value_n}
@@ -105,16 +97,6 @@ defmodule Scopes.CSys.Program do
     end
   end
 
-  def set(msg, scope) do
-    data = Shape.data(msg)
-    state = CSys.state(scope)
-    value = data[:value] || state.value
-    threshold = data[:threshold] || state.threshold
-    bias = data[:bias] || state.bias
-    state_n = %{state | value: value, threshold: threshold, bias: bias}
-    CSys.update(put_elem(scope, 0, state_n))
-  end
-
   def create_succ(msg, scope) do
     new = CSys.create(msg, restart(scope))
     data = Shape.data(msg)