diff --git a/Redcraft.FocusIME/Source/Private/Main.cpp b/Redcraft.FocusIME/Source/Private/Main.cpp
index f2b6319..84b4274 100644
--- a/Redcraft.FocusIME/Source/Private/Main.cpp
+++ b/Redcraft.FocusIME/Source/Private/Main.cpp
@@ -2,27 +2,32 @@
 
 #include <windows.h>
 #include <shellapi.h>
+#include <psapi.h>
+
 #include <iostream>
 #include <fstream>
-#include <thread>
 #include <chrono>
 #include <string>
-#include <filesystem>
 #include <ctime>
-#include <iomanip>
 #include <mutex>
+#include <atomic>
+
+#pragma comment(lib, "psapi.lib")
 
 #pragma warning(disable: 4996)
 
 // ReSharper disable CppDeprecatedEntity
 // ReSharper disable CppClangTidyCertErr33C
 
+std::mutex    GLogMutex;
 std::ofstream GLogFile;
 
-bool GShouldExit = false;
+std::atomic<bool> GShouldExit = false;
 
 void PrintLog(const std::string& Text);
 
+void CALLBACK FocusEventHookProc(HWINEVENTHOOK, DWORD Event, HWND Window, LONG, LONG, DWORD, DWORD);
+
 LRESULT CALLBACK MainWindowProc(HWND Window, UINT Message, WPARAM WParam, LPARAM LParam);
 
 int WINAPI WinMain(HINSTANCE Instance, HINSTANCE, LPSTR, int)
@@ -47,8 +52,6 @@ int WINAPI WinMain(HINSTANCE Instance, HINSTANCE, LPSTR, int)
 		return 0;
 	}
 
-	HWND MainWindow = nullptr;
-
 	WNDCLASS MainWindowClass = { };
 
 	MainWindowClass.lpfnWndProc   = MainWindowProc;
@@ -66,7 +69,7 @@ int WINAPI WinMain(HINSTANCE Instance, HINSTANCE, LPSTR, int)
 		return 1;
 	}
 
-	MainWindow = CreateWindow(
+	const HWND MainWindow = CreateWindow(
 		"FocusIME_MainWindow",
 		"FocusIME",
 		WS_OVERLAPPEDWINDOW,
@@ -74,7 +77,7 @@ int WINAPI WinMain(HINSTANCE Instance, HINSTANCE, LPSTR, int)
 		CW_USEDEFAULT, CW_USEDEFAULT,
 		nullptr, nullptr, Instance, nullptr);
 
-	if (!MainWindow)
+	if (MainWindow == nullptr)
 	{
 		MessageBox(nullptr, "Failed to create main window.", "FocusIME", MB_OK | MB_ICONERROR);
 
@@ -85,6 +88,24 @@ int WINAPI WinMain(HINSTANCE Instance, HINSTANCE, LPSTR, int)
 
 	ShowWindow(MainWindow, SW_HIDE);
 
+	const HWINEVENTHOOK FocusEventHook = SetWinEventHook(
+		EVENT_OBJECT_FOCUS, EVENT_OBJECT_FOCUS,
+		nullptr,
+		FocusEventHookProc,
+		0, 0,
+		WINEVENT_OUTOFCONTEXT | WINEVENT_SKIPOWNPROCESS);
+
+	if (FocusEventHook == nullptr)
+	{
+		MessageBox(nullptr, "Failed to set focus event hook.", "FocusIME", MB_OK | MB_ICONWARNING);
+
+		DestroyWindow(MainWindow);
+
+		CloseHandle(Mutex);
+
+		return 1;
+	}
+
 	GLogFile.open("Log.txt", std::ios::out | std::ios::app);
 
 	if (!GLogFile.is_open())
@@ -140,7 +161,13 @@ int WINAPI WinMain(HINSTANCE Instance, HINSTANCE, LPSTR, int)
 
 	PrintLog("FocusIME is shutting down...");
 
-	GLogFile.close();
+	{
+		std::lock_guard Lock(GLogMutex);
+
+		GLogFile.close();
+	}
+
+	UnhookWinEvent(FocusEventHook);
 
 	DestroyWindow(MainWindow);
 
@@ -237,6 +264,59 @@ LRESULT CALLBACK MainWindowProc(const HWND Window, const UINT Message, const WPA
 	return 0;
 }
 
+void CALLBACK FocusEventHookProc(HWINEVENTHOOK, const DWORD Event, const HWND Window, LONG, LONG, DWORD, DWORD)
+{
+	if (Event == EVENT_OBJECT_FOCUS && Window != nullptr)
+	{
+		std::string ProcessName;
+
+		do
+		{
+			DWORD PID = 0;
+
+			GetWindowThreadProcessId(Window, &PID);
+
+			const HANDLE ProcessHandle = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, PID);
+
+			if (ProcessHandle == nullptr)
+			{
+				ProcessName = "Unknown";
+
+				break;
+			}
+
+			char Buffer[MAX_PATH] = { };
+
+			if (GetModuleBaseName(ProcessHandle, nullptr, Buffer, sizeof(Buffer)) == 0)
+			{
+				CloseHandle(ProcessHandle);
+
+				ProcessName = "Unknown";
+
+				break;
+			}
+
+			CloseHandle(ProcessHandle);
+
+			ProcessName = Buffer;
+		}
+		while (false);
+
+		char Title[1024] = { };
+
+		GetWindowText(Window, Title, sizeof(Title));
+
+		std::string MessageBuffer = "Focus changed to: " + ProcessName;
+
+		if (strlen(Title) > 0)
+		{
+			MessageBuffer += " (" + std::string(Title) + ")";
+		}
+
+		PrintLog(MessageBuffer);
+	}
+}
+
 void PrintLog(const std::string& Text)
 {
 	const auto Now  = std::chrono::system_clock::now();
@@ -244,7 +324,9 @@ void PrintLog(const std::string& Text)
 
 	const long long Milliseconds = (std::chrono::duration_cast<std::chrono::milliseconds>(Now.time_since_epoch()) % 1000).count();
 
-	static std::mutex Mutex; std::lock_guard Lock(Mutex);
+	std::lock_guard Lock(GLogMutex);
+
+	if (!GLogFile.is_open()) return;
 
 	const std::tm* LocalTime = std::localtime(&Time); // NOLINT(concurrency-mt-unsafe)
 
@@ -261,6 +343,8 @@ void PrintLog(const std::string& Text)
 	Buffer[23] = Digits[Milliseconds /   1 % 10];
 
 	GLogFile << Buffer << Text << std::endl;
+
+	GLogFile.flush();
 }
 
 // ReSharper restore CppDeprecatedEntity