diff --git a/.clangd b/.clangd
index 5fb9f17..35c56ef 100644
--- a/.clangd
+++ b/.clangd
@@ -1,9 +1,9 @@
 If:
   PathMatch: [.*\.h, .*\.c] 
 CompileFlags:
-  Add: [-xc, -I/home/edgar/Codes/JacksEscape/easyx/include, -target, x86_64-pc-windows-gnu]
+  Add: [-xc, -DWIN32_LEAN_AND_MEAN, -I/home/edgar/Codes/JacksEscape/easyx/include, -target, x86_64-pc-windows-gnu]
 ---
 If:
   PathMatch: [.*\.hpp, .*\.cpp] 
 CompileFlags:
-  Add: [-xc++, -I/home/edgar/Codes/JacksEscape/easyx/include, -target, x86_64-pc-windows-gnu]
+  Add: [-xc++, -DWIN32_LEAN_AND_MEAN, -I/home/edgar/Codes/JacksEscape/easyx/include, -target, x86_64-pc-windows-gnu]
diff --git a/Main.cpp b/Main.cpp
index aed442d..466d3e3 100644
--- a/Main.cpp
+++ b/Main.cpp
@@ -1,10 +1,17 @@
 #include <graphics.h>
+#include <stdio.h>
+
+#include "Types.h"
 
 
 int main() {
+	TimePoint startup = time_Now();
+
 	initgraph(640, 480);
 	circle(200, 200, 100);
 	Sleep(5000);
 	closegraph();
+
+	printf("%.6lf seconds has elapsed\n", duration_Seconds(time_Since(startup)));
 	return 0;
 }
diff --git a/Makefile.flags b/Makefile.flags
index 8d85462..85700e7 100644
--- a/Makefile.flags
+++ b/Makefile.flags
@@ -37,7 +37,7 @@ endif
 
 export INCLUDEFLAGS := $(Platform_INCLUDEFLAGS)
 
-export CPPFLAGS =
+export CPPFLAGS = -DWIN32_LEAN_AND_MEAN
 export CFLAGS   = $(INCLUDEFLAGS) $(BUILD_OPTIONS) -O2 -Wno-attributes -flto
 export CXXFLAGS = $(INCLUDEFLAGS) -DHELOS $(BUILD_OPTIONS) $(Platform_CXXFLAGS) -O2 -Wno-unused-result -flto -std=c++17
 export LDFLAGS  = $(Platform_LDFLAGS) -s -O2 -flto
diff --git a/Types.c b/Types.c
index 0bd9f86..abfa066 100644
--- a/Types.c
+++ b/Types.c
@@ -1,5 +1,6 @@
 
 #include "Types.h"
+#include <windows.h>
 
 static inline double dmin(double x, double y) {
 	return x < y ? x : y;
@@ -70,9 +71,28 @@ Box2 box2_OffsetY(Box2 box, double offsetY) {
 }
 
 
-Duration duration_Now() {
-	// TODO Use Windows.h
+static double freqInverse = 0.0;
+
+TimePoint time_Now() {
 	// Reference: https://github.com/SFML/SFML/blob/2.6.x/src/SFML/System/Win32/ClockImpl.cpp
-	Duration d = {.microseconds = 0};
+
+	if (freqInverse == 0.0) {
+		LARGE_INTEGER freq;
+		QueryPerformanceFrequency(&freq);
+		freqInverse = 1000000.0 / ((double)freq.QuadPart);
+	}
+
+	LARGE_INTEGER time;
+	QueryPerformanceCounter(&time);
+
+	TimePoint t = {.microseconds = (int64_t)(((double)time.QuadPart) * freqInverse)};
+	return t;
+}
+
+Duration time_Since(TimePoint prev) {
+	return time_Difference(time_Now(), prev);
+}
+Duration time_Difference(TimePoint now, TimePoint prev) {
+	Duration d = {.microseconds = now.microseconds - prev.microseconds};
 	return d;
 }
diff --git a/Types.h b/Types.h
index 8b4f7ab..122db42 100644
--- a/Types.h
+++ b/Types.h
@@ -40,17 +40,20 @@ Box2 box2_OffsetY(Box2 box, double offsetY);
 
 // Time duration.
 typedef struct {
-	uint64_t microseconds;
+	int64_t microseconds;
 } Duration;
 
 static inline double duration_Seconds(const Duration t) { return ((double)t.microseconds) / 1000.0 / 1000.0; }
 static inline double duration_Milliseconds(const Duration t) { return ((double)t.microseconds) / 1000.0; }
 
-// Returns a relative duration since
-// a static time point in the past.
-//
-// Its absolute value has no meaning.
-Duration duration_Now();
+// A Time point since the start of the program.
+typedef struct {
+	int64_t microseconds;
+} TimePoint;
+
+TimePoint time_Now();
+Duration  time_Since(TimePoint prev);
+Duration  time_Difference(TimePoint now, TimePoint prev);
 
 
 #ifdef __cplusplus