diff --git a/sjplayer/src/sjplayer/CircleElementScheduledController.d b/sjplayer/src/sjplayer/CircleElementScheduledController.d
new file mode 100644
index 0000000..6c13c63
--- /dev/null
+++ b/sjplayer/src/sjplayer/CircleElementScheduledController.d
@@ -0,0 +1,48 @@
+/// License: MIT
+module sjplayer.CircleElementScheduledController;
+
+import gl4d;
+
+import sjscript;
+
+import sjplayer.CircleElement,
+       sjplayer.ScheduledControllerInterface,
+       sjplayer.VarStoreInterface;
+
+///
+class CircleElementScheduledController :
+  AbstractScheduledControllerWithOperationImpl {
+ public:
+  ///
+  this(
+      CircleElement        element,
+      in VarStoreInterface varstore,
+      in ParametersBlock[] operations) {
+    super(varstore, operations);
+    element_ = element;
+  }
+
+ protected:
+  override void PrepareOperation(ref in ParametersBlock params) {
+    element_.alive        = true;
+    element_.damage       = 0;
+    element_.nearness_coe = 0;
+    element_.matrix       = mat3.identity;
+    element_.weight       = 1;
+    element_.smooth       = 0;
+    element_.color        = vec4(1, 1, 1, 1);
+  }
+  override void FinalizeOperation(ref in ParametersBlock params) {
+    element_.alive = false;
+  }
+
+  override float GetVariable(string name) const {
+    throw new Exception("not implemented");  // TODO:
+  }
+  override void SetParameter(ref in Parameter param) {
+    throw new Exception("not implemented");  // TODO:
+  }
+
+ private:
+  CircleElement element_;
+}
diff --git a/sjplayer/src/sjplayer/ScheduledControllerInterface.d b/sjplayer/src/sjplayer/ScheduledControllerInterface.d
index 404238d..1572c89 100644
--- a/sjplayer/src/sjplayer/ScheduledControllerInterface.d
+++ b/sjplayer/src/sjplayer/ScheduledControllerInterface.d
@@ -2,11 +2,14 @@
 module sjplayer.ScheduledControllerInterface;
 
 import std.algorithm,
-       std.array;
+       std.array,
+       std.exception,
+       std.format;
 
 import sjscript;
 
-import sjplayer.util.compare;
+import sjplayer.VarStoreInterface,
+       sjplayer.util.compare;
 
 ///
 interface ScheduledControllerInterface {
@@ -34,7 +37,7 @@ abstract class AbstractScheduledController : ScheduledControllerInterface {
         ProcessOperation(*last_operation);
         return;
       }
-      FinishOperation(*last_operation);
+      FinalizeOperation(*last_operation);
     }
 
     if (next_operation_index_ >= operations_.length) return;
@@ -51,7 +54,7 @@ abstract class AbstractScheduledController : ScheduledControllerInterface {
 
   abstract void ProcessOperation(ref in ParametersBlock params);
 
-  abstract void FinishOperation(ref in ParametersBlock params);
+  abstract void FinalizeOperation(ref in ParametersBlock params);
 
  private:
   const ParametersBlock[] operations_;
@@ -60,3 +63,48 @@ abstract class AbstractScheduledController : ScheduledControllerInterface {
 
   size_t next_operation_index_;
 }
+
+///
+abstract class AbstractScheduledControllerWithOperationImpl :
+  AbstractScheduledController {
+ public:
+  ///
+  this(in VarStoreInterface varstore, in ParametersBlock[] operations) {
+    super(operations);
+    varstore_ = varstore;
+  }
+
+ protected:
+  static struct VarStore {
+   public:
+    float opIndex(string name) {
+      float result = void;
+      if (!this_.GetVariable(name).collectException(result)) return result;
+      if (!this_.varstore_[name]  .collectException(result)) return result;
+      if (!this_.user_vars_[name] .collectException(result)) return result;
+      throw new Exception("unknown variable %s".format(name));
+    }
+   private:
+    AbstractScheduledControllerWithOperationImpl this_;
+  }
+
+  override void ProcessOperation(ref in ParametersBlock params) {
+    foreach (const ref param; params.parameters) {
+      if (param.name.length >= 2 && param.name[0..2] == "__") {
+        user_vars_[param.name[2..$]] =
+          param.rhs.CalculateExpression(VarStore(this));
+        continue;
+      }
+      SetParameter(param);
+    }
+  }
+
+  abstract float GetVariable(string name) const;
+
+  abstract void SetParameter(ref in Parameter param);
+
+ private:
+  const VarStoreInterface varstore_;
+
+  float[string] user_vars_;
+}
diff --git a/sjscript/src/sjscript/package.d b/sjscript/src/sjscript/package.d
index 8e696eb..d594ae8 100644
--- a/sjscript/src/sjscript/package.d
+++ b/sjscript/src/sjscript/package.d
@@ -13,6 +13,7 @@ import sjscript.Token,
 public {
   import sjscript.Expression,
          sjscript.ParametersBlock,
+         sjscript.calculate,
          sjscript.exception;
 }