diff --git a/sjplayer/src/sjplayer/AbstractScheduledController.d b/sjplayer/src/sjplayer/AbstractScheduledController.d
new file mode 100644
index 0000000..7a3b300
--- /dev/null
+++ b/sjplayer/src/sjplayer/AbstractScheduledController.d
@@ -0,0 +1,105 @@
+/// License: MIT
+module sjplayer.AbstractScheduledController;
+
+import std.algorithm,
+       std.exception,
+       std.typecons;
+
+import sjscript;
+
+import sjplayer.ScheduledControllerInterface,
+       sjplayer.VarStoreInterface,
+       sjplayer.util.Parameter,
+       sjplayer.util.Period;
+
+///
+abstract class AbstractScheduledController : ScheduledControllerInterface {
+ public:
+  ///
+  this(in VarStoreInterface varstore, in ParametersBlock[] operations) {
+    varstore_   = varstore;
+    operations_ = operations;
+  }
+
+  override void Operate(float time) {
+    FinalizeCurrentOperationIfEnded(time);
+    PrepareNextOperationIfStarted(time);
+    ProcessCurrentOperationIfAvailable(time);
+  }
+
+ protected:
+  static struct VarStore {
+   public:
+    float opIndex(string name) const {
+      if (!time_.isNull && name == "time") return time_.get;
+      return this_.GetVariable(name);
+    }
+   private:
+    AbstractScheduledController this_;
+    Nullable!float              time_;
+  }
+
+  void PrepareOperation(ref in ParametersBlock params) {
+    user_vars_.clear();
+
+    auto vars = VarStore(this);
+    params.parameters.
+      filter!(x => x.type == ParameterType.OnceAssign).
+      each  !(x => SetParameter(x, vars));
+  }
+  void ProcessOperation(float time, ref in ParametersBlock params) {
+    auto vars = VarStore(this, time.nullable);
+    params.parameters.
+      filter!(x => x.type != ParameterType.OnceAssign).
+      each  !(x => SetParameter(x, vars));
+  }
+  void FinalizeOperation(ref in ParametersBlock params) {
+  }
+
+  float GetVariable(string name) const {
+    if (name in user_vars_) return user_vars_[name];
+    return varstore_[name];
+  }
+  void SetParameter(ref in Parameter param, ref in VarStore vars) {
+    (param.name.length >= 2 && param.name[0..2] == "__").
+      enforce("user defined variables must be prefixed '__'");
+    user_vars_[param.name] = 0;
+    param.CalculateParameter(user_vars_[param.name], vars);
+  }
+
+ private:
+  void FinalizeCurrentOperationIfEnded(float time) {
+    if (next_operation_index_ < 1) return;
+
+    const current = &operations_[next_operation_index_-1];
+    if (current.period.end > time) return;
+
+    FinalizeOperation(*current);
+  }
+  void PrepareNextOperationIfStarted(float time) {
+    if (next_operation_index_ >= operations_.length) return;
+
+    const next = &operations_[next_operation_index_];
+    if (next.period.start > time) return;
+
+    ++next_operation_index_;
+    PrepareOperation(*next);
+  }
+  void ProcessCurrentOperationIfAvailable(float time) {
+    if (next_operation_index_ < 1) return;
+
+    const current = &operations_[next_operation_index_-1];
+    if (current.period.end <= time) return;
+
+    ProcessOperation(
+        current.period.ConvertToRelativeTime(time), *current);
+  }
+
+  const VarStoreInterface varstore_;
+
+  const ParametersBlock[] operations_;
+
+  size_t next_operation_index_;
+
+  float[string] user_vars_;
+}
diff --git a/sjplayer/src/sjplayer/CircleElement.d b/sjplayer/src/sjplayer/CircleElement.d
index b5ce776..6032ea5 100644
--- a/sjplayer/src/sjplayer/CircleElement.d
+++ b/sjplayer/src/sjplayer/CircleElement.d
@@ -7,7 +7,8 @@ import std.algorithm,
 
 import gl4d;
 
-import sjplayer.ElementInterface;
+import sjplayer.ElementDrawerInterface,
+       sjplayer.ElementInterface;
 
 ///
 class CircleElement : ElementInterface {
@@ -24,7 +25,8 @@ class CircleElement : ElementInterface {
     align(1) vec4 color = vec4(0, 0, 0, 0);
   }
 
-  override void Initialize() {
+  ///
+  void Initialize() {
     alive        = false;
     damage       = 0;
     nearness_coe = 0;
diff --git a/sjplayer/src/sjplayer/CircleElementScheduledController.d b/sjplayer/src/sjplayer/CircleElementScheduledController.d
index bef3459..977bb6f 100644
--- a/sjplayer/src/sjplayer/CircleElementScheduledController.d
+++ b/sjplayer/src/sjplayer/CircleElementScheduledController.d
@@ -4,6 +4,7 @@ module sjplayer.CircleElementScheduledController;
 import std.typecons;
 
 import sjplayer.CircleElement,
+       sjplayer.ElementScheduledControllerFactory,
        sjplayer.ScheduledController;
 
 ///
diff --git a/sjplayer/src/sjplayer/Context.d b/sjplayer/src/sjplayer/Context.d
index f2e1217..bc19403 100644
--- a/sjplayer/src/sjplayer/Context.d
+++ b/sjplayer/src/sjplayer/Context.d
@@ -9,6 +9,7 @@ import sjscript;
 
 import sjplayer.Background,
        sjplayer.ContextBuilderInterface,
+       sjplayer.ElementDrawerInterface,
        sjplayer.ElementInterface,
        sjplayer.ProgramSet,
        sjplayer.ScheduledControllerInterface,
diff --git a/sjplayer/src/sjplayer/ContextBuilderInterface.d b/sjplayer/src/sjplayer/ContextBuilderInterface.d
index ec15b46..0092e77 100644
--- a/sjplayer/src/sjplayer/ContextBuilderInterface.d
+++ b/sjplayer/src/sjplayer/ContextBuilderInterface.d
@@ -1,7 +1,8 @@
 /// License: MIT
 module sjplayer.ContextBuilderInterface;
 
-import sjplayer.ElementInterface,
+import sjplayer.ElementDrawerInterface,
+       sjplayer.ElementInterface,
        sjplayer.ScheduledControllerInterface;
 
 ///
diff --git a/sjplayer/src/sjplayer/ElementDrawerInterface.d b/sjplayer/src/sjplayer/ElementDrawerInterface.d
new file mode 100644
index 0000000..9efe992
--- /dev/null
+++ b/sjplayer/src/sjplayer/ElementDrawerInterface.d
@@ -0,0 +1,9 @@
+/// License: MIT
+module sjplayer.ElementDrawerInterface;
+
+///
+interface ElementDrawerInterface {
+ public:
+  ///
+  void Draw();
+}
diff --git a/sjplayer/src/sjplayer/ElementInterface.d b/sjplayer/src/sjplayer/ElementInterface.d
index b52c6e0..a1a2fe6 100644
--- a/sjplayer/src/sjplayer/ElementInterface.d
+++ b/sjplayer/src/sjplayer/ElementInterface.d
@@ -14,16 +14,6 @@ interface ElementInterface {
     float nearness;
   }
 
-  ///
-  void Initialize();
-
   ///
   DamageCalculationResult CalculateDamage(vec2 p1, vec2 p2) const;
 }
-
-///
-interface ElementDrawerInterface {
- public:
-  ///
-  void Draw();
-}
diff --git a/sjplayer/src/sjplayer/ElementScheduledControllerFactory.d b/sjplayer/src/sjplayer/ElementScheduledControllerFactory.d
new file mode 100644
index 0000000..1b386d1
--- /dev/null
+++ b/sjplayer/src/sjplayer/ElementScheduledControllerFactory.d
@@ -0,0 +1,98 @@
+/// License: MIT
+module sjplayer.ElementScheduledControllerFactory;
+
+import sjscript;
+
+import std.algorithm,
+       std.array,
+       std.conv,
+       std.meta,
+       std.range.primitives,
+       std.traits;
+
+import sjplayer.ContextBuilderInterface,
+       sjplayer.ElementDrawerInterface,
+       sjplayer.ElementInterface,
+       sjplayer.ProgramSet,
+       sjplayer.ScheduledControllerInterface,
+       sjplayer.VarStoreInterface,
+       sjplayer.util.Period;
+
+///
+struct ElementScheduledControllerFactory(ScheduledController, ElementDrawer)
+  if (is(ScheduledController : ScheduledControllerInterface) &&
+      is(ElementDrawer : ElementDrawerInterface)) {
+ public:
+  /// ScheduledController's first constructor's first argument type.
+  alias Element =
+    Parameters!(__traits(getOverloads, ScheduledController, "__ctor")[0])[0];
+
+  static assert(is(Element : ElementInterface));
+
+  /// ElementDrawer's first constructor's first argument type.
+  alias ElementProgram =
+    Parameters!(__traits(getOverloads, ElementDrawer, "__ctor")[0])[0];
+
+  static assert(staticIndexOf!(
+        ElementProgram, ProgramSet.Programs.Types) >= 0);
+  static assert(is(Element[] :
+    Parameters!(__traits(getOverloads, ElementDrawer, "__ctor")[0])[1]));
+
+  ///
+  this(ProgramSet programs, VarStoreInterface varstore) {
+    program_  = programs.Get!ElementProgram;
+    varstore_ = varstore;
+  }
+
+  ///
+  void Create(R)(R params, ContextBuilderInterface builder)
+      if (isInputRange!R && is(ElementType!R == ParametersBlock)) {
+    auto parallelized = ParallelizeParams(params);
+    auto elements     = appender!(Element[]);
+
+    foreach (ref serial; parallelized) {
+      auto element = new Element;
+      elements    ~= element;
+      builder.AddElement(element);
+      builder.AddScheduledController(
+          new ScheduledController(element, varstore_, serial));
+    }
+    if (elements[].length > 0) {
+      builder.AddElementDrawer(new ElementDrawer(program_, elements[]));
+    }
+  }
+
+ private:
+  static ParametersBlock[][] ParallelizeParams(R)(R params)
+      if (isInputRange!R && is(ElementType!R == ParametersBlock)) {
+    ParametersBlock[][] parallelized;
+    foreach (ref param; params) {
+      auto inserted = false;
+      foreach (ref serial; parallelized) {
+        const found_index = serial.
+          countUntil!(x => x.period.start > param.period.start);
+        const insert_index =
+          found_index >= 0? found_index.to!size_t: serial.length;
+
+        const intersect_prev = insert_index >= 1 &&
+          IsPeriodIntersectedToPeriod(serial[insert_index-1].period, param.period);
+        const intersect_next = insert_index < serial.length &&
+          IsPeriodIntersectedToPeriod(serial[insert_index].period, param.period);
+
+        if (!intersect_prev && !intersect_next) {
+          serial   = serial[0..insert_index]~ param ~serial[insert_index..$];
+          inserted = true;
+          break;
+        }
+      }
+      if (!inserted) {
+        parallelized ~= [param];
+      }
+    }
+    return parallelized;
+  }
+
+  ElementProgram program_;
+
+  VarStoreInterface varstore_;
+}
diff --git a/sjplayer/src/sjplayer/ScheduledController.d b/sjplayer/src/sjplayer/ScheduledController.d
index c6b5acc..9b9cd49 100644
--- a/sjplayer/src/sjplayer/ScheduledController.d
+++ b/sjplayer/src/sjplayer/ScheduledController.d
@@ -1,60 +1,51 @@
 /// License: MIT
 module sjplayer.ScheduledController;
 
-import std.algorithm,
-       std.array,
-       std.conv,
-       std.meta,
-       std.range.primitives,
-       std.traits,
+import std.traits,
        std.typecons;
 
 import gl4d;
 
 import sjscript;
 
-import sjplayer.ContextBuilderInterface,
-       sjplayer.ElementInterface,
-       sjplayer.ProgramSet,
+import sjplayer.AbstractScheduledController,
        sjplayer.ScheduledControllerInterface,
        sjplayer.VarStoreInterface,
        sjplayer.util.MatrixFactory,
-       sjplayer.util.Parameter,
-       sjplayer.util.Period;
+       sjplayer.util.Parameter;
 
 ///
 class ScheduledController(
-    Element, string[string] ParameterNameMap) :
-  AbstractScheduledControllerWithOperationImpl {
+    Target, string[string] ParameterNameMap) : AbstractScheduledController {
  public:
   ///
   enum AliveManagementAvailable =
-    is(typeof((Element e) => e.alive)) &&
-    is(ReturnType!((Element e) => e.alive) == bool);
+    is(typeof((Target x) => x.alive)) &&
+    is(ReturnType!((Target x) => x.alive) == bool);
   ///
   enum MatrixModificationAvailable =
-    is(typeof((Element e) => e.matrix)) &&
-    is(ReturnType!((Element e) => e.matrix) == mat3);
+    is(typeof((Target x) => x.matrix)) &&
+    is(ReturnType!((Target x) => x.matrix) == mat3);
   ///
   enum AutoInitializationAvailable =
-    is(typeof((Element e) => e.Initialize()));
+    is(typeof((Target x) => x.Initialize()));
 
   ///
   this(
-      Element element,
+      Target target,
       in VarStoreInterface varstore,
       in ParametersBlock[] operations) {
     super(varstore, operations);
-    element_ = element;
+    target_ = target;
   }
 
  protected:
   override void PrepareOperation(ref in ParametersBlock params) {
     static if (AutoInitializationAvailable) {
-      element_.Initialize();
+      target_.Initialize();
     }
     static if (AliveManagementAvailable) {
-      element_.alive = true;
+      target_.alive = true;
     }
     static if (MatrixModificationAvailable) {
       matrix_factory_ = matrix_factory_.init;
@@ -64,12 +55,12 @@ class ScheduledController(
   override void ProcessOperation(float time, ref in ParametersBlock params) {
     super.ProcessOperation(time, params);
     static if (MatrixModificationAvailable) {
-      element_.matrix = matrix_factory_.Create().transposed;
+      target_.matrix = matrix_factory_.Create().transposed;
     }
   }
   override void FinalizeOperation(ref in ParametersBlock params) {
     static if (AliveManagementAvailable) {
-      element_.alive = false;
+      target_.alive = false;
     }
   }
 
@@ -77,17 +68,16 @@ class ScheduledController(
     switch (name) {
       static foreach (map_name, code; ParameterNameMap) {
         case map_name:
-          return mixin("element_."~code);
+          return mixin("target_."~code);
       }
       default: return super.GetVariable(name);
     }
   }
-  override void SetParameter(Nullable!float time, ref in Parameter param) {
-    auto vars = VarStore(this, time);
+  override void SetParameter(ref in Parameter param, ref in VarStore vars) {
     switch (param.name) {
       static foreach (map_name, code; ParameterNameMap) {
         case map_name:
-          param.CalculateParameter(mixin("element_."~code), vars);
+          param.CalculateParameter(mixin("target_."~code), vars);
           return;
       }
       default:
@@ -95,90 +85,12 @@ class ScheduledController(
     static if (MatrixModificationAvailable) {
       if (param.CalculateMatrixParameter(matrix_factory_, vars)) return;
     }
-    super.SetParameter(time, param);
+    super.SetParameter(param, vars);
   }
 
-  Element element_;
+  Target target_;
 
   static if (MatrixModificationAvailable) {
     MatrixFactory matrix_factory_;
   }
 }
-
-///
-struct ElementScheduledControllerFactory(ScheduledController, ElementDrawer)
-  if (is(ScheduledController : ScheduledControllerInterface) &&
-      is(ElementDrawer : ElementDrawerInterface)) {
- public:
-  /// ScheduledController's first constructor's first argument type.
-  alias Element =
-    Parameters!(__traits(getOverloads, ScheduledController, "__ctor")[0])[0];
-
-  static assert(is(Element : ElementInterface));
-
-  /// ElementDrawer's first constructor's first argument type.
-  alias ElementProgram =
-    Parameters!(__traits(getOverloads, ElementDrawer, "__ctor")[0])[0];
-
-  static assert(staticIndexOf!(
-        ElementProgram, ProgramSet.Programs.Types) >= 0);
-  static assert(is(Element[] :
-    Parameters!(__traits(getOverloads, ElementDrawer, "__ctor")[0])[1]));
-
-  ///
-  this(ProgramSet programs, VarStoreInterface varstore) {
-    program_  = programs.Get!ElementProgram;
-    varstore_ = varstore;
-  }
-
-  ///
-  void Create(R)(R params, ContextBuilderInterface builder)
-      if (isInputRange!R && is(ElementType!R == ParametersBlock)) {
-    auto parallelized = params.ParallelizeParams();
-    auto elements     = appender!(Element[]);
-
-    foreach (ref serial; parallelized) {
-      auto element = new Element;
-      elements    ~= element;
-      builder.AddElement(element);
-      builder.AddScheduledController(
-          new ScheduledController(element, varstore_, serial));
-    }
-    if (elements[].length > 0) {
-      builder.AddElementDrawer(new ElementDrawer(program_, elements[]));
-    }
-  }
-
- private:
-  ElementProgram    program_;
-  VarStoreInterface varstore_;
-}
-
-private ParametersBlock[][] ParallelizeParams(R)(R params)
-    if (isInputRange!R && is(ElementType!R == ParametersBlock)) {
-  ParametersBlock[][] parallelized;
-  foreach (ref param; params) {
-    auto inserted = false;
-    foreach (ref serial; parallelized) {
-      const found_index = serial.
-        countUntil!(x => x.period.start > param.period.start);
-      const insert_index =
-        found_index >= 0? found_index.to!size_t: serial.length;
-
-      const intersect_prev = insert_index >= 1 &&
-        IsPeriodIntersectedToPeriod(serial[insert_index-1].period, param.period);
-      const intersect_next = insert_index < serial.length &&
-        IsPeriodIntersectedToPeriod(serial[insert_index].period, param.period);
-
-      if (!intersect_prev && !intersect_next) {
-        serial   = serial[0..insert_index]~ param ~serial[insert_index..$];
-        inserted = true;
-        break;
-      }
-    }
-    if (!inserted) {
-      parallelized ~= [param];
-    }
-  }
-  return parallelized;
-}
diff --git a/sjplayer/src/sjplayer/ScheduledControllerInterface.d b/sjplayer/src/sjplayer/ScheduledControllerInterface.d
index eb4c40e..9014887 100644
--- a/sjplayer/src/sjplayer/ScheduledControllerInterface.d
+++ b/sjplayer/src/sjplayer/ScheduledControllerInterface.d
@@ -1,121 +1,9 @@
 /// License: MIT
 module sjplayer.ScheduledControllerInterface;
 
-import std.algorithm,
-       std.array,
-       std.exception,
-       std.format,
-       std.typecons;
-
-import sjscript;
-
-import sjplayer.VarStoreInterface,
-       sjplayer.util.Parameter,
-       sjplayer.util.Period;
-
 ///
 interface ScheduledControllerInterface {
  public:
   ///
   void Operate(float time);
 }
-
-///
-abstract class AbstractScheduledController : ScheduledControllerInterface {
- public:
-  /// The operations must be sorted.
-  this(in ParametersBlock[] operations) {
-    operations_ = operations;
-  }
-
-  override void Operate(float time) {
-    scope(exit) last_operation_time_ = time;
-
-    if (next_operation_index_ >= 1) {
-      assert(next_operation_index_ <= operations_.length);
-
-      const last_operation = &operations_[next_operation_index_-1];
-      const period         = last_operation.period;
-      if (IsTimeInPeriod(time, period)) {
-        ProcessOperation(period.ConvertToRelativeTime(time), *last_operation);
-        return;
-      }
-      FinalizeOperation(*last_operation);
-    }
-
-    if (next_operation_index_ >= operations_.length) return;
-
-    const next_operation = &operations_[next_operation_index_];
-    if (IsTimeInPeriod(time, next_operation.period)) {
-      PrepareOperation(*next_operation);
-      ProcessOperation(
-          next_operation.period.ConvertToRelativeTime(time), *next_operation);
-      ++next_operation_index_;
-    }
-  }
-
- protected:
-  abstract void PrepareOperation(ref in ParametersBlock params);
-
-  abstract void ProcessOperation(float time, ref in ParametersBlock params);
-
-  abstract void FinalizeOperation(ref in ParametersBlock params);
-
- private:
-  const ParametersBlock[] operations_;
-
-  float last_operation_time_ = -1;
-
-  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) {
-      if (!time_.isNull && name == "time") return time_.get;
-      return this_.GetVariable(name);
-    }
-   private:
-    AbstractScheduledControllerWithOperationImpl this_;
-    Nullable!float time_;
-  }
-
-  override void PrepareOperation(ref in ParametersBlock params) {
-    user_vars_.clear();
-    params.parameters.
-      filter!(x => x.type == ParameterType.OnceAssign).
-      each  !(x => SetParameter(Nullable!float.init, x));
-  }
-  override void ProcessOperation(float time, ref in ParametersBlock params) {
-    params.parameters.
-      filter!(x => x.type != ParameterType.OnceAssign).
-      each  !(x => SetParameter(time.nullable, x));
-  }
-
-  float GetVariable(string name) const {
-    if (name in user_vars_) return user_vars_[name];
-    return varstore_[name];
-  }
-  void SetParameter(Nullable!float time, ref in Parameter param) {
-    (param.name.length >= 2 && param.name[0..2] == "__").
-      enforce("user defined variables must be prefixed '__'");
-    user_vars_[param.name] = 0;
-    param.CalculateParameter(user_vars_[param.name], VarStore(this, time));
-  }
-
- private:
-  const VarStoreInterface varstore_;
-
-  float[string] user_vars_;
-}
diff --git a/sjplayer/src/sjplayer/util/Period.d b/sjplayer/src/sjplayer/util/Period.d
index 72660dc..628f94b 100644
--- a/sjplayer/src/sjplayer/util/Period.d
+++ b/sjplayer/src/sjplayer/util/Period.d
@@ -4,7 +4,7 @@ module sjplayer.util.Period;
 import sjscript;
 
 ///
-bool IsTimeInPeriod(float time, in Period period) {
+bool IsTimeInPeriod(in Period period, float time) {
   return period.start <= time && time < period.end;
 }