diff --git a/mirai-core/src/androidMain/kotlin/net/mamoe/mirai/MiraiEnvironment.kt b/mirai-core/src/androidMain/kotlin/net/mamoe/mirai/MiraiEnvironment.kt
index ffc9c1147..d69de63b4 100644
--- a/mirai-core/src/androidMain/kotlin/net/mamoe/mirai/MiraiEnvironment.kt
+++ b/mirai-core/src/androidMain/kotlin/net/mamoe/mirai/MiraiEnvironment.kt
@@ -1,3 +1,5 @@
 package net.mamoe.mirai
 
-actual object MiraiEnvironment
\ No newline at end of file
+actual object MiraiEnvironment {
+    actual val platform: Platform get() = Platform.ANDROID
+}
\ No newline at end of file
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/Bot.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/Bot.kt
index 84005160f..91e702f8d 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/Bot.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/Bot.kt
@@ -74,7 +74,7 @@ class Bot(val account: BotAccount, val logger: MiraiLogger) {
         configuration: BotNetworkConfiguration,
         cause: Throwable? = null
     ): LoginResult {
-        logger.warning("Reinitializing BotNetworkHandler")
+        logger.info("Initializing BotNetworkHandler")
         try {
             network.close(cause)
         } catch (e: Exception) {
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/MiraiEnvironment.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/MiraiEnvironment.kt
index 48de9a22e..d691f0728 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/MiraiEnvironment.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/MiraiEnvironment.kt
@@ -1,3 +1,10 @@
 package net.mamoe.mirai
 
-expect object MiraiEnvironment
\ No newline at end of file
+expect object MiraiEnvironment {
+    val platform: Platform
+}
+
+enum class Platform {
+    ANDROID,
+    JVM
+}
\ No newline at end of file
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/Event.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/Event.kt
index b71b54e85..2dd85f7ba 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/Event.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/Event.kt
@@ -3,9 +3,7 @@
 package net.mamoe.mirai.event
 
 import kotlinx.coroutines.*
-import net.mamoe.mirai.contact.Contact
 import net.mamoe.mirai.event.internal.broadcastInternal
-import net.mamoe.mirai.network.BotNetworkHandler
 import net.mamoe.mirai.utils.DefaultLogger
 import net.mamoe.mirai.utils.MiraiLogger
 import kotlin.coroutines.CoroutineContext
@@ -31,7 +29,7 @@ abstract class Event {
         } else throw UnsupportedOperationException()
 
     /**
-     * 取消事件. 事件需实现 [Cancellable] 才可以被取消, 否则调用这个方法将会得到 [UnsupportedOperationException]
+     * 取消事件. 事件需实现 [Cancellable] 才可以被取消
      *
      * @throws UnsupportedOperationException 如果事件没有实现 [Cancellable]
      */
@@ -48,7 +46,7 @@ abstract class Event {
 
 internal object EventLogger : MiraiLogger by DefaultLogger("Event")
 
-val EventDebuggingFlag: Boolean by lazy {
+private val EventDebuggingFlag: Boolean by lazy {
     false
 }
 
@@ -83,20 +81,8 @@ suspend fun <E : Event> E.broadcast(context: CoroutineContext = EmptyCoroutineCo
     }
 }
 
-/**
- * 事件协程调度器.
- *
- * JVM: 共享 [Dispatchers.Default]
- */
 internal expect val EventDispatcher: CoroutineDispatcher
 
-/**
- * 事件协程作用域.
- * 所有的事件 [broadcast] 过程均在此作用域下运行.
- *
- * 然而, 若在事件处理过程中使用到 [Contact.sendMessage] 等会 [发送数据包][BotNetworkHandler.sendPacket] 的方法,
- * 发送过程将会通过 [withContext] 将协程切换到 [BotNetworkHandler] 作用域下执行.
- */
 object EventScope : CoroutineScope {
     override val coroutineContext: CoroutineContext =
         EventDispatcher + CoroutineExceptionHandler { _, e ->
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/TIMBotNetworkHandler.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/TIMBotNetworkHandler.kt
index f98a7ae78..de90ea5fb 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/TIMBotNetworkHandler.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/TIMBotNetworkHandler.kt
@@ -329,7 +329,7 @@ internal class TIMBotNetworkHandler internal constructor(override val bot: Bot)
                 else -> {
                     error("No decrypter found")
                 }
-            } as D
+            } as? D ?: error("Internal error: could not cast decrypter found for factory to class Decrypter")
 
         suspend fun onPacketReceived(packet: Any) {//complex function, but it doesn't matter
             when (packet) {
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/packet/Packet.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/packet/Packet.kt
index 9d12da1d3..902cf6f0b 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/packet/Packet.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/network/protocol/tim/packet/Packet.kt
@@ -158,6 +158,8 @@ enum class KnownPacketId(override inline val value: UShort, override inline val
     override fun toString(): String = factory.let { it::class.simpleName } ?: this.name
 }
 
+// endregion
+
 object IgnoredPacket : Packet
 
 sealed class EventPacket {
@@ -195,7 +197,7 @@ sealed class EventPacket {
     ) : Packet
 
     @CorrespondingEvent(GroupMessageEvent::class)
-    class GroupMessage : Packet {
+    class GroupMessage : Packet { // TODO: 2019/11/6 改为 data class
         var groupNumber: UInt = 0u
             internal set
         var qq: UInt = 0u
@@ -231,7 +233,6 @@ object UnknownPacket : Packet {
  */
 object NoPacket : Packet
 
-// endregion
 
 // region Internal utils
 
diff --git a/mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/MiraiEnvironmentJvm.kt b/mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/MiraiEnvironmentJvm.kt
index 39e3e4681..48a351e49 100644
--- a/mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/MiraiEnvironmentJvm.kt
+++ b/mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/MiraiEnvironmentJvm.kt
@@ -2,6 +2,6 @@
 
 package net.mamoe.mirai
 
-actual typealias MiraiEnvironment = MiraiEnvironmentJvm
-
-object MiraiEnvironmentJvm
\ No newline at end of file
+actual object MiraiEnvironment {
+    actual val platform: Platform get() = Platform.JVM
+}
\ No newline at end of file