diff --git a/Makefile b/Makefile
index a016647..e607452 100644
--- a/Makefile
+++ b/Makefile
@@ -12,5 +12,8 @@ console:
 clean:
 	${SBT} clean
 
-.PHONY: build test console clean
+bench: clean
+	${SBT} mogCoreJVM/test:run mogCoreJS/test:run
+
+.PHONY: build test console clean bench
 
diff --git a/js/src/test/scala/com/mogproject/mogami/bench/BenchmarkJS.scala b/js/src/test/scala/com/mogproject/mogami/bench/BenchmarkJS.scala
new file mode 100644
index 0000000..f027100
--- /dev/null
+++ b/js/src/test/scala/com/mogproject/mogami/bench/BenchmarkJS.scala
@@ -0,0 +1,27 @@
+package com.mogproject.mogami.bench
+
+import com.mogproject.mogami.core.BitBoard
+import com.mogproject.mogami.core.Ptype.{PROOK, ROOK}
+import com.mogproject.mogami.core.PieceConstant._
+import com.mogproject.mogami.core.SquareConstant._
+
+
+/**
+  * Benchmarks for Scala.js
+  */
+object BenchmarkJS extends scalajs.js.JSApp with Benchmark with TestData {
+  def main(): Unit = {
+    benchAttack(BP, None, BitBoard.empty, BitBoard.empty)
+
+    benchAttack(BP, Some(P55), BitBoard.empty, BitBoard.empty)
+
+    benchAttack(BPR, Some(P11), BitBoard.empty, BitBoard.empty)
+    benchAttack(BPR, Some(P11), BitBoard.full, BitBoard.full)
+
+    benchAttack(BPB, Some(P55), BitBoard.empty, BitBoard.empty)
+    benchAttack(BPB, Some(P55), BitBoard.full, BitBoard.full)
+
+    benchGameLoading(recordSfen01)
+    benchGameLoading(recordSfen02)
+  }
+}
diff --git a/shared/src/main/scala/com/mogproject/mogami/core/Game.scala b/shared/src/main/scala/com/mogproject/mogami/core/Game.scala
index cfa773f..1f51674 100644
--- a/shared/src/main/scala/com/mogproject/mogami/core/Game.scala
+++ b/shared/src/main/scala/com/mogproject/mogami/core/Game.scala
@@ -13,15 +13,25 @@ import scala.util.Try
 case class Game(initialState: State = State.HIRATE,
                 moves: Seq[Move] = Seq.empty,
                 gameInfo: GameInfo = GameInfo(),
-                movesOffset: Int = 0
+                movesOffset: Int = 0,
+                givenHistory: Option[Seq[State]] = None
                ) extends CsaLike with SfenLike {
 
   require(history.length == moves.length + 1, "all moves must be valid")
 
   import com.mogproject.mogami.core.Game.GameStatus._
 
+  override def equals(obj: scala.Any): Boolean = obj match {
+    case that: Game =>
+      // ignore givenHistory
+      initialState == that.initialState && moves == that.moves && gameInfo == that.gameInfo && movesOffset == that.movesOffset
+    case _ => false
+  }
+
   /** history of states */
-  lazy val history: Seq[State] = moves.scanLeft(Some(initialState): Option[State])((s, m) => s.flatMap(_.makeMove(m))).flatten
+  lazy val history: Seq[State] = {
+    givenHistory.getOrElse(moves.scanLeft(Some(initialState): Option[State])((s, m) => s.flatMap(_.makeMove(m))).flatten)
+  }
 
   lazy val hashCodes: Seq[Int] = history.map(_.hashCode())
 
@@ -49,8 +59,9 @@ case class Game(initialState: State = State.HIRATE,
 
   def turn: Player = currentState.turn
 
-  def makeMove(move: Move): Option[Game] =
-    (status == Playing && currentState.isValidMove(move)).option(this.copy(moves = moves :+ move))
+  def makeMove(move: Move): Option[Game] = {
+    (status == Playing && currentState.isValidMove(move)).option(this.copy(moves = moves :+ move, givenHistory = currentState.makeMove(move).map(history :+ _)))
+  }
 
   def makeMove(move: MoveBuilder): Option[Game] = move.toMove(currentState).flatMap(makeMove)
 
diff --git a/shared/src/main/scala/com/mogproject/mogami/core/Move.scala b/shared/src/main/scala/com/mogproject/mogami/core/Move.scala
index 2112469..8c7a73b 100644
--- a/shared/src/main/scala/com/mogproject/mogami/core/Move.scala
+++ b/shared/src/main/scala/com/mogproject/mogami/core/Move.scala
@@ -173,6 +173,8 @@ case class Move(player: Player,
 
   def capturedPiece: Option[Piece] = captured.map(Piece(!player, _))
 
+  def moveFrom: MoveFrom = from.map(Left.apply).getOrElse(Right(Hand(player, oldPtype)))
+
   override def toCsaString: String =
     from.map(fr => MoveBuilderCsaBoard(player, fr, to, newPtype, elapsedTime))
       .getOrElse(MoveBuilderCsaHand(player, to, newPtype, elapsedTime)).toCsaString
diff --git a/shared/src/main/scala/com/mogproject/mogami/core/State.scala b/shared/src/main/scala/com/mogproject/mogami/core/State.scala
index c035ccb..d27677d 100644
--- a/shared/src/main/scala/com/mogproject/mogami/core/State.scala
+++ b/shared/src/main/scala/com/mogproject/mogami/core/State.scala
@@ -177,7 +177,12 @@ case class State(turn: Player = BLACK, board: BoardType = Map.empty, hand: HandT
     m.mapValues(_ & ~occupancy(turn)).filter(_._2.nonEmpty)
   }
 
-  // todo: consider converting to Set
+  /**
+    * Get all legal moves.
+    *
+    * @note This method can be relatively expensive.
+    * @return list of legal moves
+    */
   def legalMoves: Seq[Move] = (
     for {
       (from, bb) <- legalMovesBB
@@ -186,14 +191,6 @@ case class State(turn: Player = BLACK, board: BoardType = Map.empty, hand: HandT
       mv <- from.fold(MoveBuilderSfenBoard(_, to, promote), p => MoveBuilderSfenHand(p.ptype, to)).toMove(this)
     } yield mv).toSeq
 
-  /**
-    * Check if the move is legal.
-    *
-    * @param move move to test
-    * @return true if the move is legal
-    */
-  def isValidMove(move: Move): Boolean = legalMoves.contains(move.copy(elapsedTime = None))
-
   /** *
     * Check if the state is mated.
     *
@@ -250,6 +247,17 @@ case class State(turn: Player = BLACK, board: BoardType = Map.empty, hand: HandT
     case None => List()
   }
 
+  /**
+    * Check if the move is legal.
+    *
+    * @param move move to test
+    * @return true if the move is legal
+    */
+  def isValidMove(move: Move): Boolean = {
+    val mf = move.moveFrom
+    canAttack(mf, move.to) && getPromotionList(mf, move.to).contains(move.promote)
+  }
+
   /**
     * Check if the in-hand piece is non-empty.
     */
@@ -281,14 +289,6 @@ object State extends CsaStateReader with SfenStateReader {
   val empty = State(BLACK, Map.empty, EMPTY_HANDS)
   lazy val capacity: Map[Ptype, Int] = Map(PAWN -> 18, LANCE -> 4, KNIGHT -> 4, SILVER -> 4, GOLD -> 4, BISHOP -> 2, ROOK -> 2, KING -> 2)
 
-  /**
-    * Get the square where the turn-to-move player's king.
-    *
-    * @return None if the king is not on board
-    */
-  def getKingSquare(player: Player, board: BoardType): Option[Square] =
-    board.view.filter { case (s, p) => p == Piece(player, KING) }.map(_._1).headOption
-
   // constant states
   val HIRATE = State(BLACK, Map(
     Square(1, 1) -> Piece(WHITE, LANCE),
diff --git a/shared/src/main/scala/com/mogproject/mogami/util/BenchmarkUtil.scala b/shared/src/main/scala/com/mogproject/mogami/util/BenchmarkUtil.scala
new file mode 100644
index 0000000..c67169c
--- /dev/null
+++ b/shared/src/main/scala/com/mogproject/mogami/util/BenchmarkUtil.scala
@@ -0,0 +1,12 @@
+package com.mogproject.mogami.util
+
+object BenchmarkUtil {
+  def withTime[A](label: String)(thunk: => A): A = {
+    val start = System.currentTimeMillis()
+    val ret = thunk
+    val end = System.currentTimeMillis()
+    println(s"${label}: ${(end - start) / 1000.0}s")
+    ret
+  }
+
+}
diff --git a/shared/src/test/scala/com/mogproject/mogami/bench/Benchmark.scala b/shared/src/test/scala/com/mogproject/mogami/bench/Benchmark.scala
new file mode 100644
index 0000000..0d509ff
--- /dev/null
+++ b/shared/src/test/scala/com/mogproject/mogami/bench/Benchmark.scala
@@ -0,0 +1,57 @@
+package com.mogproject.mogami.bench
+
+import com.mogproject.mogami._
+
+import scala.io.Source
+
+/**
+  * Shared benchmark utility
+  */
+case class BenchResult(result: Seq[Double]) {
+  def average: Double = if (result.isEmpty) 0.0 else result.sum / result.length / 1000
+
+  def maxValue: Double = result.max / 1000
+
+  def minValue: Double = result.min / 1000
+
+  def print(): Unit = {
+    println(f"\n- avg: ${average}%.3fs, min: ${minValue}s, max: ${maxValue}s\n")
+  }
+}
+
+trait Benchmark {
+
+  val benchmarkCount = 3
+  val attackRepeat = 10000
+
+  private[this] def withBenchmark(thunk: => Unit): BenchResult = {
+    val ret = (1 to benchmarkCount).map { n =>
+      val start = System.currentTimeMillis()
+      thunk
+      (System.currentTimeMillis() - start).toDouble
+    }
+    BenchResult(ret)
+  }
+
+  def benchGameLoading(sfen: String): Unit = {
+    println(s"benchGameLoading: sfen=${sfen}")
+
+    withBenchmark {
+      val g = Game.parseSfenString(sfen)
+      assert(g.isDefined)
+    }.print()
+  }
+
+  def benchAttack(piece: Piece, from: Option[Square], allOcc: BitBoard, myPawnOcc: BitBoard): Unit = {
+    println(s"benchAttack: repeat=${attackRepeat}, piece=${piece}, from=${from}, allOcc=${allOcc.toOctalString}, myPawnOcc=${myPawnOcc.toOctalString}")
+
+    withBenchmark {
+      var i = 0
+      while (i < attackRepeat) {
+        Attack.get(piece, from, allOcc, myPawnOcc)
+        i += 1
+      }
+    }.print()
+  }
+
+}
diff --git a/shared/src/test/scala/com/mogproject/mogami/bench/BenchmarkJVM.scala b/shared/src/test/scala/com/mogproject/mogami/bench/BenchmarkJVM.scala
new file mode 100644
index 0000000..79fc72e
--- /dev/null
+++ b/shared/src/test/scala/com/mogproject/mogami/bench/BenchmarkJVM.scala
@@ -0,0 +1,13 @@
+package com.mogproject.mogami.bench
+
+/**
+  * Benchmarks for Scala JVM
+  */
+object BenchmarkJVM extends Benchmark with TestData {
+
+  def main(args: Array[String]): Unit = {
+    benchGameLoading(recordSfen01)
+    benchGameLoading(recordSfen02)
+  }
+
+}
diff --git a/shared/src/test/scala/com/mogproject/mogami/bench/TestData.scala b/shared/src/test/scala/com/mogproject/mogami/bench/TestData.scala
new file mode 100644
index 0000000..a424445
--- /dev/null
+++ b/shared/src/test/scala/com/mogproject/mogami/bench/TestData.scala
@@ -0,0 +1,13 @@
+package com.mogproject.mogami.bench
+
+trait TestData {
+  val recordSfen01: String = "lnsgkgsnl/1r5b1/ppppppppp/9/9/9/PPPPPPPPP/1B5R1/LNSGKGSNL b - 0"
+  val recordSfen02: String = Seq(
+    "lnsgkgsnl/1r5b1/ppppppppp/9/9/9/PPPPPPPPP/1B5R1/LNSGKGSNL b - 0",
+    " 7g7f 3c3d 2g2f 4a3b 6i7h 8c8d 2f2e 2b8h+ 7i8h 3a2b",
+    " 3i3h 2b3c 3g3f 7a7b 5i6h 6c6d 3h3g 8d8e 3g4f 8e8f",
+    " 8g8f 8b8f 2e2d 2c2d 8i7g 8f8b 3f3e 3d3e 4f3e 7c7d",
+    " 3e2d 3c2d 2h2d P*2c 2d2f 7d7e P*8c 7b8c B*6c B*7d",
+    " 6c1h+ 7d4g+ 4i5h 4g1d"
+  ).mkString
+}