diff --git a/battle_srv/models/ringbuf.go b/battle_srv/models/ringbuf.go
index 572e4d1..295c9f5 100644
--- a/battle_srv/models/ringbuf.go
+++ b/battle_srv/models/ringbuf.go
@@ -21,6 +21,10 @@ func NewRingBuffer(n int32) *RingBuffer {
 }
 
 func (rb *RingBuffer) Put(pItem interface{}) {
+	for rb.Cnt >= rb.N-1 {
+		// Make room for the new element
+		rb.Pop()
+	}
 	rb.Eles[rb.Ed] = pItem
 	rb.EdFrameId++
 	rb.Cnt++
@@ -69,5 +73,8 @@ func (rb *RingBuffer) GetByOffset(offsetFromSt int32) interface{} {
 }
 
 func (rb *RingBuffer) GetByFrameId(frameId int32) interface{} {
+	if frameId >= rb.EdFrameId {
+		return nil
+	}
 	return rb.GetByOffset(frameId - rb.StFrameId)
 }
diff --git a/battle_srv/models/room.go b/battle_srv/models/room.go
index aea745e..7a8a7bb 100644
--- a/battle_srv/models/room.go
+++ b/battle_srv/models/room.go
@@ -335,10 +335,6 @@ func (pR *Room) ConvertToGeneratingRenderFrameId(inputFrameId int32) int32 {
 	return (inputFrameId << pR.InputScaleFrames)
 }
 
-func (pR *Room) ConvertToJustBeforeNextGeneratingRenderFrameId(inputFrameId int32) int32 {
-	return (inputFrameId << pR.InputScaleFrames) + (1 << pR.InputScaleFrames) - 1
-}
-
 func (pR *Room) ConvertToFirstUsedRenderFrameId(inputFrameId int32, inputDelayFrames int32) int32 {
 	return ((inputFrameId << pR.InputScaleFrames) + inputDelayFrames)
 }
@@ -413,7 +409,6 @@ func (pR *Room) StartBattle() {
 			pR.onBattleStoppedForSettlement()
 		}()
 
-		battleStartedAtNanos := utils.UnixtimeNano()
 		pR.LastRenderFrameIdTriggeredAt = utils.UnixtimeNano()
 
 		Logger.Info("The `battleMainLoop` is started for:", zap.Any("roomId", pR.Id))
@@ -422,11 +417,7 @@ func (pR *Room) StartBattle() {
 
 			elapsedNanosSinceLastFrameIdTriggered := stCalculation - pR.LastRenderFrameIdTriggeredAt
 			if elapsedNanosSinceLastFrameIdTriggered < pR.dilutedRollbackEstimatedDtNanos {
-				totalElapsedNanos := (stCalculation - battleStartedAtNanos)
-				serverFpsByFar := float64(pR.RenderFrameId) * float64(1000000000) / float64(totalElapsedNanos)
-				Logger.Info(fmt.Sprintf("Avoiding too fast frame@roomId=%v, renderFrameId=%v, totalElapsedNanos=%v, serverFpsByFar=%v: elapsedNanosSinceLastFrameIdTriggered=%v", pR.Id, pR.RenderFrameId, totalElapsedNanos, serverFpsByFar, elapsedNanosSinceLastFrameIdTriggered))
-				time.Sleep(time.Duration(pR.dilutedRollbackEstimatedDtNanos - elapsedNanosSinceLastFrameIdTriggered))
-				continue
+				Logger.Info(fmt.Sprintf("renderFrameId=%v@roomId=%v: Is backend running too fast? elapsedNanosSinceLastFrameIdTriggered=%v", pR.RenderFrameId, pR.Id, elapsedNanosSinceLastFrameIdTriggered))
 			}
 
 			if pR.RenderFrameId > pR.BattleDurationFrames {
@@ -461,7 +452,7 @@ func (pR *Room) StartBattle() {
 
 			   Upon resync, it's still possible that "refRenderFrameId < frontend.chaserRenderFrameId" -- and this is allowed.
 			*/
-			refRenderFrameId := pR.ConvertToJustBeforeNextGeneratingRenderFrameId(upperToSendInputFrameId)
+			refRenderFrameId := pR.ConvertToGeneratingRenderFrameId(upperToSendInputFrameId + 1) // for the frontend to jump immediately into generating & upsyncing the next input frame, thus getting rid of "resync avalanche"
 
 			dynamicsDuration := int64(0)
 			if pR.BackendDynamicsEnabled {
@@ -480,10 +471,13 @@ func (pR *Room) StartBattle() {
 			}
 
 			for playerId, player := range pR.Players {
-				if swapped := atomic.CompareAndSwapInt32(&player.BattleState, PlayerBattleStateIns.ACTIVE, PlayerBattleStateIns.ACTIVE); !swapped {
-					// [WARNING] DON'T send anything if the player is not yet active, because it could jam the channel and cause significant delay upon "battle recovery for reconnected player".
+
+				currPlayerBattleState := atomic.LoadInt32(&(player.BattleState))
+				if PlayerBattleStateIns.DISCONNECTED == currPlayerBattleState || PlayerBattleStateIns.LOST == currPlayerBattleState {
+					// [WARNING] DON'T try to send any message to an inactive player!
 					continue
 				}
+
 				if 0 == pR.RenderFrameId {
 					kickoffFrame := pR.RenderFrameBuffer.GetByFrameId(0).(*RoomDownsyncFrame)
 					pR.sendSafely(kickoffFrame, nil, DOWNSYNC_MSG_ACT_BATTLE_START, playerId)
@@ -531,14 +525,15 @@ func (pR *Room) StartBattle() {
 					   2. reconnection
 					*/
 					shouldResync1 := (MAGIC_LAST_SENT_INPUT_FRAME_ID_READDED == player.LastSentInputFrameId)
-					shouldResync2 := (0 < (unconfirmedMask & uint64(1<<uint32(player.JoinIndex-1)))) // This condition is critical, if we don't send resync upon this condition, the "reconnected or slowly-clocking player" might never get its input synced
-					// shouldResync2 := (0 < unconfirmedMask) // An easier version of the above, might keep sending "refRenderFrame"s to still connected players when any player is disconnected
+					// shouldResync2 := (0 < (unconfirmedMask & uint64(1<<uint32(player.JoinIndex-1)))) // This condition is critical, if we don't send resync upon this condition, the "reconnected or slowly-clocking player" might never get its input synced
+					shouldResync2 := (0 < unconfirmedMask) // An easier version of the above, might keep sending "refRenderFrame"s to still connected players when any player is disconnected
 					if pR.BackendDynamicsEnabled && (shouldResync1 || shouldResync2) {
 						tmp := pR.RenderFrameBuffer.GetByFrameId(refRenderFrameId)
 						if nil == tmp {
 							panic(fmt.Sprintf("Required refRenderFrameId=%v for roomId=%v, playerId=%v, candidateToSendInputFrameId=%v doesn't exist! InputsBuffer=%v, RenderFrameBuffer=%v", refRenderFrameId, pR.Id, playerId, candidateToSendInputFrameId, pR.InputsBufferString(false), pR.RenderFrameBufferString()))
 						}
 						refRenderFrame := tmp.(*RoomDownsyncFrame)
+						refRenderFrame.BackendUnconfirmedMask = unconfirmedMask
 						pR.sendSafely(refRenderFrame, toSendInputFrames, DOWNSYNC_MSG_ACT_FORCED_RESYNC, playerId)
 					} else {
 						pR.sendSafely(nil, toSendInputFrames, DOWNSYNC_MSG_ACT_INPUT_BATCH, playerId)
@@ -549,7 +544,7 @@ func (pR *Room) StartBattle() {
 
 			if pR.BackendDynamicsEnabled {
 				// Evict no longer required "RenderFrameBuffer"
-				for pR.RenderFrameBuffer.N < pR.RenderFrameBuffer.Cnt || (0 < pR.RenderFrameBuffer.Cnt && pR.RenderFrameBuffer.StFrameId < refRenderFrameId) {
+				for 0 < pR.RenderFrameBuffer.Cnt && pR.RenderFrameBuffer.StFrameId < refRenderFrameId {
 					_ = pR.RenderFrameBuffer.Pop()
 				}
 			}
@@ -572,7 +567,7 @@ func (pR *Room) StartBattle() {
 			if minLastSentInputFrameId < minToKeepInputFrameId {
 				minToKeepInputFrameId = minLastSentInputFrameId
 			}
-			for pR.InputsBuffer.N < pR.InputsBuffer.Cnt || (0 < pR.InputsBuffer.Cnt && pR.InputsBuffer.StFrameId < minToKeepInputFrameId) {
+			for 0 < pR.InputsBuffer.Cnt && pR.InputsBuffer.StFrameId < minToKeepInputFrameId {
 				f := pR.InputsBuffer.Pop().(*InputFrameDownsync)
 				if pR.inputFrameIdDebuggable(f.InputFrameId) {
 					// Popping of an "inputFrame" would be AFTER its being all being confirmed, because it requires the "inputFrame" to be all acked
@@ -798,17 +793,17 @@ func (pR *Room) OnDismissed() {
 	pR.RenderFrameId = 0
 	pR.CurDynamicsRenderFrameId = 0
 	pR.InputDelayFrames = 8
-	pR.NstDelayFrames = pR.InputDelayFrames
+	pR.NstDelayFrames = 4
 	pR.InputScaleFrames = uint32(2)
 	pR.ServerFps = 60
 	pR.RollbackEstimatedDtMillis = 16.667  // Use fixed-and-low-precision to mitigate the inconsistent floating-point-number issue between Golang and JavaScript
 	pR.RollbackEstimatedDtNanos = 16666666 // A little smaller than the actual per frame time, just for preventing FAST FRAME
-	dilutionFactor := 12
+	dilutionFactor := 24
 	pR.dilutedRollbackEstimatedDtNanos = int64(16666666 * (dilutionFactor) / (dilutionFactor - 1)) // [WARNING] Only used in controlling "battleMainLoop" to be keep a frame rate lower than that of the frontends, such that upon resync(i.e. BackendDynamicsEnabled=true), the frontends would have bigger chances to keep up with or even surpass the backend calculation
 	pR.BattleDurationFrames = 30 * pR.ServerFps
 	pR.BattleDurationNanos = int64(pR.BattleDurationFrames) * (pR.RollbackEstimatedDtNanos + 1)
 	pR.InputFrameUpsyncDelayTolerance = 2
-	pR.MaxChasingRenderFramesPerUpdate = 5
+	pR.MaxChasingRenderFramesPerUpdate = 8
 
 	pR.BackendDynamicsEnabled = true // [WARNING] When "false", recovery upon reconnection wouldn't work!
 	pR.BackendDynamicsForceConfirmationEnabled = (pR.BackendDynamicsEnabled && true)
@@ -874,8 +869,9 @@ func (pR *Room) OnPlayerDisconnected(playerId int32) {
 		}
 	}()
 
-	if _, existent := pR.Players[playerId]; existent {
-		switch pR.Players[playerId].BattleState {
+	if player, existent := pR.Players[playerId]; existent {
+		currPlayerBattleState := atomic.LoadInt32(&(player.BattleState))
+		switch currPlayerBattleState {
 		case PlayerBattleStateIns.DISCONNECTED:
 		case PlayerBattleStateIns.LOST:
 		case PlayerBattleStateIns.EXPELLED_DURING_GAME:
@@ -889,17 +885,18 @@ func (pR *Room) OnPlayerDisconnected(playerId int32) {
 		return
 	}
 
-	switch pR.State {
+	currRoomBattleState := atomic.LoadInt32(&(pR.State))
+	switch currRoomBattleState {
 	case RoomBattleStateIns.WAITING:
 		pR.onPlayerLost(playerId)
 		delete(pR.Players, playerId) // Note that this statement MUST be put AFTER `pR.onPlayerLost(...)` to avoid nil pointer exception.
 		if 0 == pR.EffectivePlayerCount {
-			pR.State = RoomBattleStateIns.IDLE
+			atomic.StoreInt32(&(pR.State), RoomBattleStateIns.IDLE)
 		}
 		pR.updateScore()
 		Logger.Info("Player disconnected while room is at RoomBattleStateIns.WAITING:", zap.Any("playerId", playerId), zap.Any("roomId", pR.Id), zap.Any("nowRoomBattleState", pR.State), zap.Any("nowRoomEffectivePlayerCount", pR.EffectivePlayerCount))
 	default:
-		pR.Players[playerId].BattleState = PlayerBattleStateIns.DISCONNECTED
+		atomic.StoreInt32(&(pR.Players[playerId].BattleState), PlayerBattleStateIns.DISCONNECTED)
 		pR.clearPlayerNetworkSession(playerId) // Still need clear the network session pointers, because "OnPlayerDisconnected" is only triggered from "signalToCloseConnOfThisPlayer" in "ws/serve.go", when the same player reconnects the network session pointers will be re-assigned
 		Logger.Info("Player disconnected from room:", zap.Any("playerId", playerId), zap.Any("playerBattleState", pR.Players[playerId].BattleState), zap.Any("roomId", pR.Id), zap.Any("nowRoomBattleState", pR.State), zap.Any("nowRoomEffectivePlayerCount", pR.EffectivePlayerCount))
 	}
@@ -912,7 +909,7 @@ func (pR *Room) onPlayerLost(playerId int32) {
 		}
 	}()
 	if player, existent := pR.Players[playerId]; existent {
-		player.BattleState = PlayerBattleStateIns.LOST
+		atomic.StoreInt32(&(player.BattleState), PlayerBattleStateIns.LOST)
 		pR.clearPlayerNetworkSession(playerId)
 		pR.EffectivePlayerCount--
 		indiceInJoinIndexBooleanArr := int(player.JoinIndex - 1)
diff --git a/battle_srv/protos/room_downsync_frame.pb.go b/battle_srv/protos/room_downsync_frame.pb.go
index 70f01eb..194340a 100644
--- a/battle_srv/protos/room_downsync_frame.pb.go
+++ b/battle_srv/protos/room_downsync_frame.pb.go
@@ -1059,10 +1059,11 @@ type RoomDownsyncFrame struct {
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	Id             int32                     `protobuf:"varint,1,opt,name=id,proto3" json:"id,omitempty"`
-	Players        map[int32]*PlayerDownsync `protobuf:"bytes,2,rep,name=players,proto3" json:"players,omitempty" protobuf_key:"varint,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
-	CountdownNanos int64                     `protobuf:"varint,3,opt,name=countdownNanos,proto3" json:"countdownNanos,omitempty"`
-	MeleeBullets   []*MeleeBullet            `protobuf:"bytes,4,rep,name=meleeBullets,proto3" json:"meleeBullets,omitempty"` // I don't know how to mimic inheritance/composition in protobuf by far, thus using an array for each type of bullet as a compromise
+	Id                     int32                     `protobuf:"varint,1,opt,name=id,proto3" json:"id,omitempty"`
+	Players                map[int32]*PlayerDownsync `protobuf:"bytes,2,rep,name=players,proto3" json:"players,omitempty" protobuf_key:"varint,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
+	CountdownNanos         int64                     `protobuf:"varint,3,opt,name=countdownNanos,proto3" json:"countdownNanos,omitempty"`
+	MeleeBullets           []*MeleeBullet            `protobuf:"bytes,4,rep,name=meleeBullets,proto3" json:"meleeBullets,omitempty"`                      // I don't know how to mimic inheritance/composition in protobuf by far, thus using an array for each type of bullet as a compromise
+	BackendUnconfirmedMask uint64                    `protobuf:"varint,5,opt,name=backendUnconfirmedMask,proto3" json:"backendUnconfirmedMask,omitempty"` // Indexed by "joinIndex", same compression concern as stated in InputFrameDownsync
 }
 
 func (x *RoomDownsyncFrame) Reset() {
@@ -1125,6 +1126,13 @@ func (x *RoomDownsyncFrame) GetMeleeBullets() []*MeleeBullet {
 	return nil
 }
 
+func (x *RoomDownsyncFrame) GetBackendUnconfirmedMask() uint64 {
+	if x != nil {
+		return x.BackendUnconfirmedMask
+	}
+	return 0
+}
+
 var File_room_downsync_frame_proto protoreflect.FileDescriptor
 
 var file_room_downsync_frame_proto_rawDesc = []byte{
@@ -1377,7 +1385,7 @@ var file_room_downsync_frame_proto_rawDesc = []byte{
 	0x6b, 0x65, 0x79, 0x12, 0x29, 0x0a, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x18, 0x02, 0x20, 0x01,
 	0x28, 0x0b, 0x32, 0x13, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x73, 0x2e, 0x4d, 0x65, 0x6c, 0x65,
 	0x65, 0x42, 0x75, 0x6c, 0x6c, 0x65, 0x74, 0x52, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x3a, 0x02,
-	0x38, 0x01, 0x22, 0x9a, 0x02, 0x0a, 0x11, 0x52, 0x6f, 0x6f, 0x6d, 0x44, 0x6f, 0x77, 0x6e, 0x73,
+	0x38, 0x01, 0x22, 0xd2, 0x02, 0x0a, 0x11, 0x52, 0x6f, 0x6f, 0x6d, 0x44, 0x6f, 0x77, 0x6e, 0x73,
 	0x79, 0x6e, 0x63, 0x46, 0x72, 0x61, 0x6d, 0x65, 0x12, 0x0e, 0x0a, 0x02, 0x69, 0x64, 0x18, 0x01,
 	0x20, 0x01, 0x28, 0x05, 0x52, 0x02, 0x69, 0x64, 0x12, 0x40, 0x0a, 0x07, 0x70, 0x6c, 0x61, 0x79,
 	0x65, 0x72, 0x73, 0x18, 0x02, 0x20, 0x03, 0x28, 0x0b, 0x32, 0x26, 0x2e, 0x70, 0x72, 0x6f, 0x74,
@@ -1389,14 +1397,18 @@ var file_room_downsync_frame_proto_rawDesc = []byte{
 	0x6f, 0x73, 0x12, 0x37, 0x0a, 0x0c, 0x6d, 0x65, 0x6c, 0x65, 0x65, 0x42, 0x75, 0x6c, 0x6c, 0x65,
 	0x74, 0x73, 0x18, 0x04, 0x20, 0x03, 0x28, 0x0b, 0x32, 0x13, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f,
 	0x73, 0x2e, 0x4d, 0x65, 0x6c, 0x65, 0x65, 0x42, 0x75, 0x6c, 0x6c, 0x65, 0x74, 0x52, 0x0c, 0x6d,
-	0x65, 0x6c, 0x65, 0x65, 0x42, 0x75, 0x6c, 0x6c, 0x65, 0x74, 0x73, 0x1a, 0x52, 0x0a, 0x0c, 0x50,
-	0x6c, 0x61, 0x79, 0x65, 0x72, 0x73, 0x45, 0x6e, 0x74, 0x72, 0x79, 0x12, 0x10, 0x0a, 0x03, 0x6b,
-	0x65, 0x79, 0x18, 0x01, 0x20, 0x01, 0x28, 0x05, 0x52, 0x03, 0x6b, 0x65, 0x79, 0x12, 0x2c, 0x0a,
-	0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x0b, 0x32, 0x16, 0x2e, 0x70,
-	0x72, 0x6f, 0x74, 0x6f, 0x73, 0x2e, 0x50, 0x6c, 0x61, 0x79, 0x65, 0x72, 0x44, 0x6f, 0x77, 0x6e,
-	0x73, 0x79, 0x6e, 0x63, 0x52, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x3a, 0x02, 0x38, 0x01, 0x42,
-	0x13, 0x5a, 0x11, 0x62, 0x61, 0x74, 0x74, 0x6c, 0x65, 0x5f, 0x73, 0x72, 0x76, 0x2f, 0x70, 0x72,
-	0x6f, 0x74, 0x6f, 0x73, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
+	0x65, 0x6c, 0x65, 0x65, 0x42, 0x75, 0x6c, 0x6c, 0x65, 0x74, 0x73, 0x12, 0x36, 0x0a, 0x16, 0x62,
+	0x61, 0x63, 0x6b, 0x65, 0x6e, 0x64, 0x55, 0x6e, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x72, 0x6d, 0x65,
+	0x64, 0x4d, 0x61, 0x73, 0x6b, 0x18, 0x05, 0x20, 0x01, 0x28, 0x04, 0x52, 0x16, 0x62, 0x61, 0x63,
+	0x6b, 0x65, 0x6e, 0x64, 0x55, 0x6e, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x72, 0x6d, 0x65, 0x64, 0x4d,
+	0x61, 0x73, 0x6b, 0x1a, 0x52, 0x0a, 0x0c, 0x50, 0x6c, 0x61, 0x79, 0x65, 0x72, 0x73, 0x45, 0x6e,
+	0x74, 0x72, 0x79, 0x12, 0x10, 0x0a, 0x03, 0x6b, 0x65, 0x79, 0x18, 0x01, 0x20, 0x01, 0x28, 0x05,
+	0x52, 0x03, 0x6b, 0x65, 0x79, 0x12, 0x2c, 0x0a, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x18, 0x02,
+	0x20, 0x01, 0x28, 0x0b, 0x32, 0x16, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x73, 0x2e, 0x50, 0x6c,
+	0x61, 0x79, 0x65, 0x72, 0x44, 0x6f, 0x77, 0x6e, 0x73, 0x79, 0x6e, 0x63, 0x52, 0x05, 0x76, 0x61,
+	0x6c, 0x75, 0x65, 0x3a, 0x02, 0x38, 0x01, 0x42, 0x13, 0x5a, 0x11, 0x62, 0x61, 0x74, 0x74, 0x6c,
+	0x65, 0x5f, 0x73, 0x72, 0x76, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x73, 0x62, 0x06, 0x70, 0x72,
+	0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
diff --git a/frontend/assets/resources/pbfiles/room_downsync_frame.proto b/frontend/assets/resources/pbfiles/room_downsync_frame.proto
index 6cf5c02..412087a 100644
--- a/frontend/assets/resources/pbfiles/room_downsync_frame.proto
+++ b/frontend/assets/resources/pbfiles/room_downsync_frame.proto
@@ -134,4 +134,5 @@ message RoomDownsyncFrame {
   map<int32, PlayerDownsync> players = 2;
   int64 countdownNanos = 3;
   repeated MeleeBullet meleeBullets = 4; // I don't know how to mimic inheritance/composition in protobuf by far, thus using an array for each type of bullet as a compromise 
+  uint64 backendUnconfirmedMask = 5; // Indexed by "joinIndex", same compression concern as stated in InputFrameDownsync
 }
diff --git a/frontend/assets/scenes/login.fire b/frontend/assets/scenes/login.fire
index b62a942..76a6bfa 100644
--- a/frontend/assets/scenes/login.fire
+++ b/frontend/assets/scenes/login.fire
@@ -440,7 +440,7 @@
       "array": [
         0,
         0,
-        342.9460598986377,
+        216.50635094610968,
         0,
         0,
         0,
diff --git a/frontend/assets/scripts/AttackingCharacter.js b/frontend/assets/scripts/AttackingCharacter.js
index 9a365e7..ce05c8b 100644
--- a/frontend/assets/scripts/AttackingCharacter.js
+++ b/frontend/assets/scripts/AttackingCharacter.js
@@ -96,7 +96,7 @@ cc.Class({
   _interruptPlayingAnimAndPlayNewAnimDragonBones(rdfPlayer, prevRdfPlayer, newCharacterState, newAnimName, underlyingAnimationCtrl, playingAnimName) {
     if (window.ATK_CHARACTER_STATE_INTERRUPT_WAIVE_SET.has(newCharacterState)) {
       // No "framesToRecover"
-      console.warn(`#DragonBones JoinIndex=${rdfPlayer.joinIndex}, playing new ${newAnimName} from the beginning: while the playing anim is ${playingAnimName}, player rdf changed from: ${null == prevRdfPlayer ? null : JSON.stringify(prevRdfPlayer)}, to: ${JSON.stringify(rdfPlayer)}`);
+      //console.warn(`#DragonBones JoinIndex=${rdfPlayer.joinIndex}, ${playingAnimName} -> ${newAnimName}`);
       underlyingAnimationCtrl.gotoAndPlayByFrame(newAnimName, 0, -1);
     } else {
       const animationData = underlyingAnimationCtrl._animations[newAnimName];
@@ -112,7 +112,7 @@ cc.Class({
   _interruptPlayingAnimAndPlayNewAnimFrameAnim(rdfPlayer, prevRdfPlayer, newCharacterState, newAnimName, playingAnimName) {
     if (window.ATK_CHARACTER_STATE_INTERRUPT_WAIVE_SET.has(newCharacterState)) {
       // No "framesToRecover"
-      console.warn(`#FrameAnim JoinIndex=${rdfPlayer.joinIndex}, playing new ${newAnimName} from the beginning: while the playing anim is ${playingAnimName}, player rdf changed from: ${null == prevRdfPlayer ? null : JSON.stringify(prevRdfPlayer)}, to: ${JSON.stringify(rdfPlayer)}`);
+      //console.warn(`#DragonBones JoinIndex=${rdfPlayer.joinIndex}, ${playingAnimName} -> ${newAnimName}`);
       this.animComp.play(newAnimName, 0);
       return;
     }
diff --git a/frontend/assets/scripts/Map.js b/frontend/assets/scripts/Map.js
index cf56c94..b0d0826 100644
--- a/frontend/assets/scripts/Map.js
+++ b/frontend/assets/scripts/Map.js
@@ -110,7 +110,7 @@ cc.Class({
     while (0 < self.recentRenderCache.cnt && self.recentRenderCache.stFrameId < minToKeepRenderFrameId) {
       self.recentRenderCache.pop();
     }
-    const ret = self.recentRenderCache.setByFrameId(rdf, rdf.id);
+    const [ret, oldStFrameId, oldEdFrameId] = self.recentRenderCache.setByFrameId(rdf, rdf.id);
     return ret;
   },
 
@@ -123,9 +123,12 @@ cc.Class({
     while (0 < self.recentInputCache.cnt && self.recentInputCache.stFrameId < minToKeepInputFrameId) {
       self.recentInputCache.pop();
     }
-    const ret = self.recentInputCache.setByFrameId(inputFrameDownsync, inputFrameDownsync.inputFrameId);
-    if (-1 < self.lastAllConfirmedInputFrameId && self.recentInputCache.stFrameId > self.lastAllConfirmedInputFrameId) {
-      console.error("Invalid input cache dumped! lastAllConfirmedRenderFrameId=", self.lastAllConfirmedRenderFrameId, ", lastAllConfirmedInputFrameId=", self.lastAllConfirmedInputFrameId, ", recentRenderCache=", self._stringifyRecentRenderCache(false), ", recentInputCache=", self._stringifyRecentInputCache(false));
+    const [ret, oldStFrameId, oldEdFrameId] = self.recentInputCache.setByFrameId(inputFrameDownsync, inputFrameDownsync.inputFrameId);
+    if (window.RING_BUFF_NON_CONSECUTIVE_SET == ret) {
+      throw `Failed to dump input cache#1! inputFrameDownsync.inputFrameId=${inputFrameDownsync.inputFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}; recentRenderCache=${self._stringifyRecentRenderCache(false)}, recentInputCache=${self._stringifyRecentInputCache(false)}`;
+    }
+    if (window.RING_BUFF_FAILED_TO_SET == ret) {
+      throw `Failed to dump input cache#2 (maybe recentInputCache too small)! inputFrameDownsync.inputFrameId=${inputFrameDownsync.inputFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}; recentRenderCache=${self._stringifyRecentRenderCache(false)}, recentInputCache=${self._stringifyRecentInputCache(false)}`;
     }
     return ret;
   },
@@ -153,7 +156,7 @@ cc.Class({
       null == self.ctrl ||
       null == self.selfPlayerInfo
     ) {
-      return [null, null];
+      throw `noDelayInputFrameId=${inputFrameId} couldn't be generated: recentInputCache=${self._stringifyRecentInputCache(false)}`;
     }
 
     const joinIndex = self.selfPlayerInfo.joinIndex;
@@ -163,19 +166,24 @@ cc.Class({
     // If "forceConfirmation" is active on backend, we shouldn't override the already downsynced "inputFrameDownsync"s.  
     const existingInputFrame = self.recentInputCache.getByFrameId(inputFrameId);
     if (null != existingInputFrame && self._allConfirmed(existingInputFrame.confirmedList)) {
+      console.log(`noDelayInputFrameId=${inputFrameId} already exists in recentInputCache and is all-confirmed: recentInputCache=${self._stringifyRecentInputCache(false)}`);
       return [previousSelfInput, existingInputFrame.inputList[joinIndex - 1]];
     }
     const prefabbedInputList = (null == previousInputFrameDownsyncWithPrediction ? new Array(self.playerRichInfoDict.size).fill(0) : previousInputFrameDownsyncWithPrediction.inputList.slice());
     const currSelfInput = self.ctrl.getEncodedInput();
     prefabbedInputList[(joinIndex - 1)] = currSelfInput;
-    const prefabbedInputFrameDownsync = {
+    const prefabbedInputFrameDownsync = window.pb.protos.InputFrameDownsync.create({
       inputFrameId: inputFrameId,
       inputList: prefabbedInputList,
       confirmedList: (1 << (self.selfPlayerInfo.joinIndex - 1))
-    };
+    });
 
     self.dumpToInputCache(prefabbedInputFrameDownsync); // A prefabbed inputFrame, would certainly be adding a new inputFrame to the cache, because server only downsyncs "all-confirmed inputFrames" 
 
+    if (inputFrameId >= self.recentInputCache.edFrameId) {
+      throw `noDelayInputFrameId=${inputFrameId} seems not properly dumped #1: recentInputCache=${self._stringifyRecentInputCache(false)}`;
+    }
+
     return [previousSelfInput, currSelfInput];
   },
 
@@ -203,7 +211,7 @@ cc.Class({
     for (let i = batchInputFrameIdSt; i <= latestLocalInputFrameId; ++i) {
       const inputFrameDownsync = self.recentInputCache.getByFrameId(i);
       if (null == inputFrameDownsync) {
-        console.error("sendInputFrameUpsyncBatch: recentInputCache is NOT having inputFrameId=", i, ": latestLocalInputFrameId=", latestLocalInputFrameId, ", recentInputCache=", self._stringifyRecentInputCache(false));
+        console.error(`sendInputFrameUpsyncBatch: recentInputCache is NOT having inputFrameId=i: latestLocalInputFrameId=${latestLocalInputFrameId}, recentInputCache=${self._stringifyRecentInputCache(false)}`);
       } else {
         const inputFrameUpsync = {
           inputFrameId: i,
@@ -225,6 +233,9 @@ cc.Class({
     }).finish();
     window.sendSafely(reqData);
     self.lastUpsyncInputFrameId = latestLocalInputFrameId;
+    if (self.lastUpsyncInputFrameId >= self.recentInputCache.edFrameId) {
+      throw `noDelayInputFrameId=${self.lastUpsyncInputFrameId} == latestLocalInputFrameId=${latestLocalInputFrameId} seems not properly dumped #2: recentInputCache=${self._stringifyRecentInputCache(false)}`;
+    }
   },
 
   onEnable() {
@@ -413,7 +424,9 @@ cc.Class({
     /** Init required prefab ended. */
 
     window.handleBattleColliderInfo = function(parsedBattleColliderInfo) {
+      // TODO: Upon reconnection, the backend might have already been sending down data that'd trigger "onRoomDownsyncFrame & onInputFrameDownsyncBatch", but frontend could reject those data due to "battleState != PlayerBattleState.ACTIVE".
       Object.assign(self, parsedBattleColliderInfo);
+      self.tooFastDtIntervalMillis = 0.5 * self.rollbackEstimatedDtMillis;
 
       const tiledMapIns = self.node.getComponent(cc.TiledMap);
 
@@ -574,14 +587,18 @@ cc.Class({
   onRoomDownsyncFrame(rdf) {
     // This function is also applicable to "re-joining".
     const self = window.mapIns;
-    if (rdf.id < self.lastAllConfirmedRenderFrameId) {
-      return window.RING_BUFF_FAILED_TO_SET;
+    if (!self.recentRenderCache) {
+      return;
     }
+    if (ALL_BATTLE_STATES.IN_SETTLEMENT == self.battleState) {
+      return;
+    }
+    const shouldForceDumping1 = (window.MAGIC_ROOM_DOWNSYNC_FRAME_ID.BATTLE_START == rdf.id);
+    const shouldForceDumping2 = (rdf.id > self.renderFrameId + self.renderFrameIdLagTolerance);
 
-    const dumpRenderCacheRet = self.dumpToRenderCache(rdf);
+    const dumpRenderCacheRet = (shouldForceDumping1 || shouldForceDumping2) ? self.dumpToRenderCache(rdf) : window.RING_BUFF_CONSECUTIVE_SET;
     if (window.RING_BUFF_FAILED_TO_SET == dumpRenderCacheRet) {
-      console.error("Something is wrong while setting the RingBuffer by frameId!");
-      return dumpRenderCacheRet;
+      throw `Failed to dump render cache#1 (maybe recentRenderCache too small)! rdf.id=${rdf.id}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}; recentRenderCache=${self._stringifyRecentRenderCache(false)}, recentInputCache=${self._stringifyRecentInputCache(false)}`;
     }
     if (window.MAGIC_ROOM_DOWNSYNC_FRAME_ID.BATTLE_START < rdf.id && window.RING_BUFF_CONSECUTIVE_SET == dumpRenderCacheRet) {
       /*
@@ -592,13 +609,7 @@ cc.Class({
       return dumpRenderCacheRet;
     }
 
-    // The logic below applies to ( || window.RING_BUFF_NON_CONSECUTIVE_SET == dumpRenderCacheRet)
-    if (window.MAGIC_ROOM_DOWNSYNC_FRAME_ID.BATTLE_START == rdf.id) {
-      console.log('On battle started! renderFrameId=', rdf.id);
-    } else {
-      console.log('On battle resynced! renderFrameId=', rdf.id);
-    }
-
+    // The logic below applies to (window.MAGIC_ROOM_DOWNSYNC_FRAME_ID.BATTLE_START == rdf.id || window.RING_BUFF_NON_CONSECUTIVE_SET == dumpRenderCacheRet)
     const players = rdf.players;
     self._initPlayerRichInfoDict(players);
 
@@ -612,11 +623,22 @@ cc.Class({
 
     if (null == self.renderFrameId || self.renderFrameId <= rdf.id) {
       // In fact, not having "window.RING_BUFF_CONSECUTIVE_SET == dumpRenderCacheRet" should already imply that "self.renderFrameId <= rdf.id", but here we double check and log the anomaly  
+
+      if (window.MAGIC_ROOM_DOWNSYNC_FRAME_ID.BATTLE_START == rdf.id) {
+        console.log('On battle started! renderFrameId=', rdf.id);
+      } else {
+        console.warn(`Got resync@localRenderFrameId=${self.renderFrameId} -> rdf.id=${rdf.id} & rdf.backendUnconfirmedMask=${rdf.backendUnconfirmedMask}, @lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, @lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}, @chaserRenderFrameId=${self.chaserRenderFrameId}, @localRecentInputCache=${mapIns._stringifyRecentInputCache(false)}`);
+      }
+
       self.renderFrameId = rdf.id;
       self.lastRenderFrameIdTriggeredAt = performance.now();
       // In this case it must be true that "rdf.id > chaserRenderFrameId >= lastAllConfirmedRenderFrameId".
       self.lastAllConfirmedRenderFrameId = rdf.id;
       self.chaserRenderFrameId = rdf.id;
+      const candidateLastAllConfirmedInputFrame = self._convertToInputFrameId(rdf.id - 1, self.inputDelayFrames);
+      if (self.lastAllConfirmedInputFrame < candidateLastAllConfirmedInputFrame) {
+        self.lastAllConfirmedInputFrame = candidateLastAllConfirmedInputFrame;
+      }
 
       const canvasNode = self.canvasNode;
       self.ctrl = canvasNode.getComponent("TouchEventsManager");
@@ -651,8 +673,10 @@ cc.Class({
 
   onInputFrameDownsyncBatch(batch) {
     const self = this;
-    if (ALL_BATTLE_STATES.IN_BATTLE != self.battleState
-      && ALL_BATTLE_STATES.IN_SETTLEMENT != self.battleState) {
+    if (!self.recentInputCache) {
+      return;
+    }
+    if (ALL_BATTLE_STATES.IN_SETTLEMENT == self.battleState) {
       return;
     }
 
@@ -663,6 +687,7 @@ cc.Class({
       if (inputFrameDownsyncId < self.lastAllConfirmedInputFrameId) {
         continue;
       }
+      self.lastAllConfirmedInputFrameId = inputFrameDownsyncId;
       const localInputFrame = self.recentInputCache.getByFrameId(inputFrameDownsyncId);
       if (null != localInputFrame
         &&
@@ -672,7 +697,6 @@ cc.Class({
       ) {
         firstPredictedYetIncorrectInputFrameId = inputFrameDownsyncId;
       }
-      self.lastAllConfirmedInputFrameId = inputFrameDownsyncId;
       // [WARNING] Take all "inputFrameDownsync" from backend as all-confirmed, it'll be later checked by "rollbackAndChase". 
       inputFrameDownsync.confirmedList = (1 << self.playerRichInfoDict.size) - 1;
       self.dumpToInputCache(inputFrameDownsync);
@@ -716,7 +740,7 @@ cc.Class({
   logBattleStats() {
     const self = this;
     let s = [];
-    s.push(`Battle stats: renderFrameId=${self.renderFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastUpsyncInputFrameId=${self.lastUpsyncInputFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}, chaserRenderFrameId=${self.chaserRenderFrameId}`);
+    s.push(`Battle stats: renderFrameId=${self.renderFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastUpsyncInputFrameId=${self.lastUpsyncInputFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}, chaserRenderFrameId=${self.chaserRenderFrameId}; recentRenderCache=${self._stringifyRecentRenderCache(false)}, recentInputCache=${self._stringifyRecentInputCache(false)}`);
 
     for (let i = self.recentInputCache.stFrameId; i < self.recentInputCache.edFrameId; ++i) {
       const inputFrameDownsync = self.recentInputCache.getByFrameId(i);
@@ -761,7 +785,8 @@ cc.Class({
     const [wx, wy] = self.virtualGridToWorldPos(vx, vy);
     newPlayerNode.setPosition(wx, wy);
     playerScriptIns.mapNode = self.node;
-    const colliderWidth = playerDownsyncInfo.colliderRadius * 2, colliderHeight = playerDownsyncInfo.colliderRadius * 3; 
+    const colliderWidth = playerDownsyncInfo.colliderRadius * 2,
+      colliderHeight = playerDownsyncInfo.colliderRadius * 3;
     const [x0, y0] = self.virtualGridToPolygonColliderAnchorPos(vx, vy, colliderWidth, colliderHeight),
       pts = [[0, 0], [colliderWidth, 0], [colliderWidth, colliderHeight], [0, colliderHeight]];
 
@@ -783,7 +808,8 @@ cc.Class({
     const self = this;
     if (ALL_BATTLE_STATES.IN_BATTLE == self.battleState) {
       const elapsedMillisSinceLastFrameIdTriggered = performance.now() - self.lastRenderFrameIdTriggeredAt;
-      if (elapsedMillisSinceLastFrameIdTriggered < (self.rollbackEstimatedDtMillis)) {
+      if (elapsedMillisSinceLastFrameIdTriggered < self.tooFastDtIntervalMillis) {
+        // [WARNING] We should avoid a frontend ticking too fast to prevent cheating, as well as ticking too slow to cause a "resync avalanche" that impacts user experience!
         // console.debug("Avoiding too fast frame@renderFrameId=", self.renderFrameId, ": elapsedMillisSinceLastFrameIdTriggered=", elapsedMillisSinceLastFrameIdTriggered);
         return;
       }
@@ -822,17 +848,13 @@ cc.Class({
         */
         // [WARNING] Don't try to get "prevRdf(i.e. renderFrameId == latest-1)" by "self.recentRenderCache.getByFrameId(...)" here, as the cache might have been updated by asynchronous "onRoomDownsyncFrame(...)" calls!
         self.applyRoomDownsyncFrameDynamics(rdf, prevRdf);
+        ++self.renderFrameId; // [WARNING] It's important to increment the renderFrameId AFTER all the operations above!!!
+        self.lastRenderFrameIdTriggeredAt = performance.now();
         let t3 = performance.now();
       } catch (err) {
         console.error("Error during Map.update", err);
+        self.onBattleStopped(); // TODO: Popup to ask player to refresh browser
       } finally {
-        // Update countdown
-        self.countdownNanos = self.battleDurationNanos - self.renderFrameId * self.rollbackEstimatedDtNanos;
-        if (self.countdownNanos <= 0) {
-          self.onBattleStopped(self.playerRichInfoDict);
-          return;
-        }
-
         const countdownSeconds = parseInt(self.countdownNanos / 1000000000);
         if (isNaN(countdownSeconds)) {
           console.warn(`countdownSeconds is NaN for countdownNanos == ${self.countdownNanos}.`);
@@ -840,8 +862,6 @@ cc.Class({
         if (null != self.countdownLabel) {
           self.countdownLabel.string = countdownSeconds;
         }
-        ++self.renderFrameId; // [WARNING] It's important to increment the renderFrameId AFTER all the operations above!!!
-        self.lastRenderFrameIdTriggeredAt = performance.now();
       }
     }
   },
@@ -967,15 +987,21 @@ cc.Class({
       playerRichInfo.scriptIns.updateSpeed(immediatePlayerInfo.speed);
       playerRichInfo.scriptIns.updateCharacterAnim(immediatePlayerInfo, prevRdfPlayer, false);
     }
+
+    // Update countdown
+    self.countdownNanos = self.battleDurationNanos - self.renderFrameId * self.rollbackEstimatedDtNanos;
+    if (self.countdownNanos <= 0) {
+      self.onBattleStopped(self.playerRichInfoDict);
+    }
   },
 
   getCachedInputFrameDownsyncWithPrediction(inputFrameId) {
     const self = this;
-    let inputFrameDownsync = self.recentInputCache.getByFrameId(inputFrameId);
-    if (null != inputFrameDownsync && -1 != self.lastAllConfirmedInputFrameId && inputFrameId > self.lastAllConfirmedInputFrameId) {
-      const lastAllConfirmedInputFrame = self.recentInputCache.getByFrameId(self.lastAllConfirmedInputFrameId);
+    const inputFrameDownsync = self.recentInputCache.getByFrameId(inputFrameId);
+    const lastAllConfirmedInputFrame = self.recentInputCache.getByFrameId(self.lastAllConfirmedInputFrameId);
+    if (null != inputFrameDownsync && null != lastAllConfirmedInputFrame && inputFrameId > self.lastAllConfirmedInputFrameId) {
       for (let i = 0; i < inputFrameDownsync.inputList.length; ++i) {
-        if (i == self.selfPlayerInfo.joinIndex - 1) continue;
+        if (i == (self.selfPlayerInfo.joinIndex - 1)) continue;
         inputFrameDownsync.inputList[i] = (lastAllConfirmedInputFrame.inputList[i] & 15); // Don't predict attack input!
       }
     }
@@ -1007,11 +1033,7 @@ cc.Class({
       };
     }
 
-    const toRet = {
-      id: currRenderFrame.id + 1,
-      players: nextRenderFramePlayers,
-      meleeBullets: []
-    };
+    const nextRenderFrameMeleeBullets = [];
 
     const bulletPushbacks = new Array(self.playerRichInfoArr.length); // Guaranteed determinism regardless of traversal order
     const effPushbacks = new Array(self.playerRichInfoArr.length); // Guaranteed determinism regardless of traversal order
@@ -1104,7 +1126,7 @@ cc.Class({
         collisionSysMap.delete(collisionBulletIndex);
       }
       if (removedBulletsAtCurrFrame.has(collisionBulletIndex)) continue;
-      toRet.meleeBullets.push(meleeBullet);
+      nextRenderFrameMeleeBullets.push(meleeBullet);
     }
 
     // Process player inputs
@@ -1145,7 +1167,7 @@ cc.Class({
             punch.offenderJoinIndex = joinIndex;
             punch.offenderPlayerId = playerId;
             punch.originatedRenderFrameId = currRenderFrame.id;
-            toRet.meleeBullets.push(punch);
+            nextRenderFrameMeleeBullets.push(punch);
             // console.log(`A rising-edge of meleeBullet is created at renderFrame.id=${currRenderFrame.id}, delayedInputFrame.id=${delayedInputFrame.inputFrameId}: ${self._stringifyRecentInputCache(true)}`);
             // console.log(`A rising-edge of meleeBullet is created at renderFrame.id=${currRenderFrame.id}, delayedInputFrame.id=${delayedInputFrame.inputFrameId}`);
 
@@ -1198,7 +1220,11 @@ cc.Class({
 
     }
 
-    return toRet;
+    return window.pb.protos.RoomDownsyncFrame.create({
+      id: currRenderFrame.id + 1,
+      players: nextRenderFramePlayers,
+      meleeBullets: nextRenderFrameMeleeBullets,
+    });
   },
 
   rollbackAndChase(renderFrameIdSt, renderFrameIdEd, collisionSys, collisionSysMap, isChasing) {
@@ -1206,31 +1232,24 @@ cc.Class({
     This function eventually calculates a "RoomDownsyncFrame" where "RoomDownsyncFrame.id == renderFrameIdEd" if not interruptted.
     */
     const self = this;
-    let prevLatestRdf = null;
-    let latestRdf = self.recentRenderCache.getByFrameId(renderFrameIdSt); // typed "RoomDownsyncFrame"
-    if (null == latestRdf) {
-      console.error(`Couldn't find renderFrameId=${renderFrameIdSt}, to rollback, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}, recentRenderCache=${self._stringifyRecentRenderCache(false)}, recentInputCache=${self._stringifyRecentInputCache(false)}`);
-      return [prevLatestRdf, latestRdf];
-    }
+    let i = renderFrameIdSt,
+      prevLatestRdf = null,
+      latestRdf = null;
 
-    if (renderFrameIdSt >= renderFrameIdEd) {
-      return [prevLatestRdf, latestRdf];
-    }
-
-    for (let i = renderFrameIdSt; i < renderFrameIdEd; ++i) {
-      const currRenderFrame = self.recentRenderCache.getByFrameId(i); // typed "RoomDownsyncFrame"; [WARNING] When "true == isChasing", this function can be interruptted by "onRoomDownsyncFrame(rdf)" asynchronously anytime, making this line return "null"!
-      if (null == currRenderFrame) {
+    do {
+      latestRdf = self.recentRenderCache.getByFrameId(i); // typed "RoomDownsyncFrame"; [WARNING] When "true == isChasing", this function can be interruptted by "onRoomDownsyncFrame(rdf)" asynchronously anytime, making this line return "null"!
+      if (null == latestRdf) {
         console.warn(`Couldn't find renderFrame for i=${i} to rollback, self.renderFrameId=${self.renderFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}, might've been interruptted by onRoomDownsyncFrame`);
         return [prevLatestRdf, latestRdf];
       }
       const j = self._convertToInputFrameId(i, self.inputDelayFrames);
       const delayedInputFrame = self.getCachedInputFrameDownsyncWithPrediction(j);
       if (null == delayedInputFrame) {
-        console.warn(`Failed to get cached delayedInputFrame for i=${i}, j=${j}, self.renderFrameId=${self.renderFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}`);
-        return [prevLatestRdf, latestRdf];
+        // Shouldn't happen!
+        throw `Failed to get cached delayedInputFrame for i=${i}, j=${j}, renderFrameId=${self.renderFrameId}, lastAllConfirmedRenderFrameId=${self.lastAllConfirmedRenderFrameId}, lastUpsyncInputFrameId=${self.lastUpsyncInputFrameId}, lastAllConfirmedInputFrameId=${self.lastAllConfirmedInputFrameId}, chaserRenderFrameId=${self.chaserRenderFrameId}; recentRenderCache=${self._stringifyRecentRenderCache(false)}, recentInputCache=${self._stringifyRecentInputCache(false)}`;
       }
       prevLatestRdf = latestRdf;
-      latestRdf = self.applyInputFrameDownsyncDynamicsOnSingleRenderFrame(delayedInputFrame, currRenderFrame, collisionSys, collisionSysMap);
+      latestRdf = self.applyInputFrameDownsyncDynamicsOnSingleRenderFrame(delayedInputFrame, prevLatestRdf, collisionSys, collisionSysMap);
       if (
         self._allConfirmed(delayedInputFrame.confirmedList)
         &&
@@ -1249,7 +1268,8 @@ cc.Class({
         self.chaserRenderFrameId = latestRdf.id;
       }
       self.dumpToRenderCache(latestRdf);
-    }
+      ++i;
+    } while (i < renderFrameIdEd);
 
     return [prevLatestRdf, latestRdf];
   },
diff --git a/frontend/assets/scripts/RingBuffer.js b/frontend/assets/scripts/RingBuffer.js
index 52c1ea0..f8d4094 100644
--- a/frontend/assets/scripts/RingBuffer.js
+++ b/frontend/assets/scripts/RingBuffer.js
@@ -13,6 +13,10 @@ var RingBuffer = function(capacity) {
 };
 
 RingBuffer.prototype.put = function(item) {
+  while (this.cnt >= this.n - 1) {
+    // Make room for the new element
+    this.pop();
+  }
   this.eles[this.ed] = item
   this.edFrameId++;
   this.cnt++;
@@ -61,40 +65,41 @@ RingBuffer.prototype.getArrIdxByOffset = function(offsetFromSt) {
 };
 
 RingBuffer.prototype.getByFrameId = function(frameId) {
+  if (frameId >= this.edFrameId) return null;
   const arrIdx = this.getArrIdxByOffset(frameId - this.stFrameId);
   return (null == arrIdx ? null : this.eles[arrIdx]);
 };
 
 // [WARNING] During a battle, frontend could receive non-consecutive frames (either renderFrame or inputFrame) due to resync, the buffer should handle these frames properly. 
 RingBuffer.prototype.setByFrameId = function(item, frameId) {
+  const oldStFrameId = this.stFrameId,
+    oldEdFrameId = this.edFrameId;
   if (frameId < this.stFrameId) {
-    console.error("Invalid putByFrameId#1: stFrameId=", this.stFrameId, ", edFrameId=", this.edFrameId, ", incoming item=", item);
-    return window.RING_BUFF_FAILED_TO_SET;
+    return [window.RING_BUFF_FAILED_TO_SET, oldStFrameId, oldEdFrameId];
   }
-  const arrIdx = this.getArrIdxByOffset(frameId - this.stFrameId);
-  if (null != arrIdx) {
-    this.eles[arrIdx] = item; 
-    return window.RING_BUFF_CONSECUTIVE_SET;
+  // By now "this.stFrameId <= frameId"
+
+  if (this.edFrameId > frameId) {
+    const arrIdx = this.getArrIdxByOffset(frameId - this.stFrameId);
+    if (null != arrIdx) {
+      this.eles[arrIdx] = item;
+      return [window.RING_BUFF_CONSECUTIVE_SET, oldStFrameId, oldEdFrameId];
+    }
   }
 
-  // When "null == arrIdx", should it still be deemed consecutive if "frameId == edFrameId" prior to the reset?
+  // By now "this.edFrameId <= frameId"
   let ret = window.RING_BUFF_CONSECUTIVE_SET;
   if (this.edFrameId < frameId) {
     this.st = this.ed = 0;
     this.stFrameId = this.edFrameId = frameId;
     this.cnt = 0;
     ret = window.RING_BUFF_NON_CONSECUTIVE_SET;
+  } else {
+    // this.edFrameId == frameId 
+    this.put(item);
   }
 
-  this.eles[this.ed] = item
-  this.edFrameId++;
-  this.cnt++;
-  this.ed++;
-  if (this.ed >= this.n) {
-    this.ed -= this.n; // Deliberately not using "%" operator for performance concern
-  }
-
-  return ret;
+  return [ret, oldStFrameId, oldEdFrameId];
 };
 
 module.exports = RingBuffer;
diff --git a/frontend/assets/scripts/WsSessionMgr.js b/frontend/assets/scripts/WsSessionMgr.js
index 30cb349..98646c5 100644
--- a/frontend/assets/scripts/WsSessionMgr.js
+++ b/frontend/assets/scripts/WsSessionMgr.js
@@ -177,8 +177,6 @@ ${JSON.stringify(resp, null, 2)}`);
             return;
           }
           const inputFrameIdConsecutive = (resp.inputFrameDownsyncBatch[0].inputFrameId == mapIns.lastAllConfirmedInputFrameId + 1);
-          const renderFrameIdConsecutive = (resp.rdf.id <= mapIns.renderFrameId + mapIns.renderFrameIdLagTolerance);
-          console.warn(`Got resync@localRenderFrameId=${mapIns.renderFrameId}, @lastAllConfirmedRenderFrameId=${mapIns.lastAllConfirmedRenderFrameId}, @lastAllConfirmedInputFrameId=${mapIns.lastAllConfirmedInputFrameId}, @chaserRenderFrameId=${mapIns.chaserRenderFrameId}, @localRecentInputCache=${mapIns._stringifyRecentInputCache(false)}, inputFrameIdConsecutive=${inputFrameIdConsecutive}, renderFrameIdConsecutive=${renderFrameIdConsecutive}`);
           // The following order of execution is important 
           mapIns.onRoomDownsyncFrame(resp.rdf);
           mapIns.onInputFrameDownsyncBatch(resp.inputFrameDownsyncBatch);
diff --git a/frontend/assets/scripts/modules/room_downsync_frame_proto_bundle.forcemsg.js b/frontend/assets/scripts/modules/room_downsync_frame_proto_bundle.forcemsg.js
index 070c8f7..9b5e86e 100644
--- a/frontend/assets/scripts/modules/room_downsync_frame_proto_bundle.forcemsg.js
+++ b/frontend/assets/scripts/modules/room_downsync_frame_proto_bundle.forcemsg.js
@@ -5082,6 +5082,7 @@ $root.protos = (function() {
          * @property {Object.<string,protos.PlayerDownsync>|null} [players] RoomDownsyncFrame players
          * @property {number|Long|null} [countdownNanos] RoomDownsyncFrame countdownNanos
          * @property {Array.<protos.MeleeBullet>|null} [meleeBullets] RoomDownsyncFrame meleeBullets
+         * @property {number|Long|null} [backendUnconfirmedMask] RoomDownsyncFrame backendUnconfirmedMask
          */
 
         /**
@@ -5133,6 +5134,14 @@ $root.protos = (function() {
          */
         RoomDownsyncFrame.prototype.meleeBullets = $util.emptyArray;
 
+        /**
+         * RoomDownsyncFrame backendUnconfirmedMask.
+         * @member {number|Long} backendUnconfirmedMask
+         * @memberof protos.RoomDownsyncFrame
+         * @instance
+         */
+        RoomDownsyncFrame.prototype.backendUnconfirmedMask = $util.Long ? $util.Long.fromBits(0,0,true) : 0;
+
         /**
          * Creates a new RoomDownsyncFrame instance using the specified properties.
          * @function create
@@ -5169,6 +5178,8 @@ $root.protos = (function() {
             if (message.meleeBullets != null && message.meleeBullets.length)
                 for (var i = 0; i < message.meleeBullets.length; ++i)
                     $root.protos.MeleeBullet.encode(message.meleeBullets[i], writer.uint32(/* id 4, wireType 2 =*/34).fork()).ldelim();
+            if (message.backendUnconfirmedMask != null && Object.hasOwnProperty.call(message, "backendUnconfirmedMask"))
+                writer.uint32(/* id 5, wireType 0 =*/40).uint64(message.backendUnconfirmedMask);
             return writer;
         };
 
@@ -5240,6 +5251,10 @@ $root.protos = (function() {
                         message.meleeBullets.push($root.protos.MeleeBullet.decode(reader, reader.uint32()));
                         break;
                     }
+                case 5: {
+                        message.backendUnconfirmedMask = reader.uint64();
+                        break;
+                    }
                 default:
                     reader.skipType(tag & 7);
                     break;
@@ -5304,6 +5319,9 @@ $root.protos = (function() {
                         return "meleeBullets." + error;
                 }
             }
+            if (message.backendUnconfirmedMask != null && message.hasOwnProperty("backendUnconfirmedMask"))
+                if (!$util.isInteger(message.backendUnconfirmedMask) && !(message.backendUnconfirmedMask && $util.isInteger(message.backendUnconfirmedMask.low) && $util.isInteger(message.backendUnconfirmedMask.high)))
+                    return "backendUnconfirmedMask: integer|Long expected";
             return null;
         };
 
@@ -5350,6 +5368,15 @@ $root.protos = (function() {
                     message.meleeBullets[i] = $root.protos.MeleeBullet.fromObject(object.meleeBullets[i]);
                 }
             }
+            if (object.backendUnconfirmedMask != null)
+                if ($util.Long)
+                    (message.backendUnconfirmedMask = $util.Long.fromValue(object.backendUnconfirmedMask)).unsigned = true;
+                else if (typeof object.backendUnconfirmedMask === "string")
+                    message.backendUnconfirmedMask = parseInt(object.backendUnconfirmedMask, 10);
+                else if (typeof object.backendUnconfirmedMask === "number")
+                    message.backendUnconfirmedMask = object.backendUnconfirmedMask;
+                else if (typeof object.backendUnconfirmedMask === "object")
+                    message.backendUnconfirmedMask = new $util.LongBits(object.backendUnconfirmedMask.low >>> 0, object.backendUnconfirmedMask.high >>> 0).toNumber(true);
             return message;
         };
 
@@ -5377,6 +5404,11 @@ $root.protos = (function() {
                     object.countdownNanos = options.longs === String ? long.toString() : options.longs === Number ? long.toNumber() : long;
                 } else
                     object.countdownNanos = options.longs === String ? "0" : 0;
+                if ($util.Long) {
+                    var long = new $util.Long(0, 0, true);
+                    object.backendUnconfirmedMask = options.longs === String ? long.toString() : options.longs === Number ? long.toNumber() : long;
+                } else
+                    object.backendUnconfirmedMask = options.longs === String ? "0" : 0;
             }
             if (message.id != null && message.hasOwnProperty("id"))
                 object.id = message.id;
@@ -5396,6 +5428,11 @@ $root.protos = (function() {
                 for (var j = 0; j < message.meleeBullets.length; ++j)
                     object.meleeBullets[j] = $root.protos.MeleeBullet.toObject(message.meleeBullets[j], options);
             }
+            if (message.backendUnconfirmedMask != null && message.hasOwnProperty("backendUnconfirmedMask"))
+                if (typeof message.backendUnconfirmedMask === "number")
+                    object.backendUnconfirmedMask = options.longs === String ? String(message.backendUnconfirmedMask) : message.backendUnconfirmedMask;
+                else
+                    object.backendUnconfirmedMask = options.longs === String ? $util.Long.prototype.toString.call(message.backendUnconfirmedMask) : options.longs === Number ? new $util.LongBits(message.backendUnconfirmedMask.low >>> 0, message.backendUnconfirmedMask.high >>> 0).toNumber(true) : message.backendUnconfirmedMask;
             return object;
         };