diff --git a/Component_Physics.h b/Component_Physics.h
new file mode 100644
index 0000000..c05337e
--- /dev/null
+++ b/Component_Physics.h
@@ -0,0 +1,36 @@
+#pragma once
+
+#include "Types.h"
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+typedef struct Entity;
+extern double Physics_Gravity;
+
+
+typedef struct {
+	Entity *super;
+	double x, y;
+	double vecX, vecY;
+} Component_Position;
+
+
+// Box is relative to Position if exists
+// if not, Box is absolute
+//
+// Moving hitboxes only hits fixed hitboxes
+typedef struct {
+	Entity *super;
+	Box2 box;
+	bool fixed;
+} Component_Hitbox;
+
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/Entity.h b/Entity.h
new file mode 100644
index 0000000..f4d9d52
--- /dev/null
+++ b/Entity.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <stdint.h>
+#include "util/vector.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+// Entity.
+typedef struct {
+	uintptr_t type;
+	const char *name;
+
+} Entity;
+
+
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/JacksEscape.vcxproj b/JacksEscape.vcxproj
index a9c53ef..d5f2d30 100644
--- a/JacksEscape.vcxproj
+++ b/JacksEscape.vcxproj
@@ -127,6 +127,9 @@
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
+    <ClInclude Include="Component_Physics.h" />
+    <ClInclude Include="Entity.h" />
+    <ClInclude Include="Types.h" />
     <ClInclude Include="util\minmax.h" />
     <ClInclude Include="util\queue.h" />
     <ClInclude Include="util\tree.h" />
@@ -134,6 +137,7 @@
     <ClInclude Include="util\vector.h" />
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="Types.c" />
     <ClCompile Include="util\queue.c" />
     <ClCompile Include="util\tree.c" />
     <ClCompile Include="util\vector.c" />
diff --git a/JacksEscape.vcxproj.filters b/JacksEscape.vcxproj.filters
index 3f5ce82..d714b85 100644
--- a/JacksEscape.vcxproj.filters
+++ b/JacksEscape.vcxproj.filters
@@ -33,6 +33,15 @@
     <ClInclude Include="util\vector.h">
       <Filter>Util</Filter>
     </ClInclude>
+    <ClInclude Include="Entity.h">
+      <Filter>头文件</Filter>
+    </ClInclude>
+    <ClInclude Include="Component_Physics.h">
+      <Filter>头文件</Filter>
+    </ClInclude>
+    <ClInclude Include="Types.h">
+      <Filter>头文件</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="util\queue.c">
@@ -44,5 +53,8 @@
     <ClCompile Include="util\vector.c">
       <Filter>Util</Filter>
     </ClCompile>
+    <ClCompile Include="Types.c">
+      <Filter>源文件</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/Types.c b/Types.c
new file mode 100644
index 0000000..75553b6
--- /dev/null
+++ b/Types.c
@@ -0,0 +1,57 @@
+
+#include "Types.h"
+
+static inline double dmin(double x, double y) {
+	return x < y ? x : y;
+}
+static inline double dmax(double x, double y) {
+	return x > y ? x : y;
+}
+
+
+Vec2 vec2_Add(Vec2 x, Vec2 y) {
+	Vec2 result = {
+		.x = x.x + y.x,
+		.y = x.y + y.y};
+	return result;
+}
+
+Vec2 vec2_Scale(Vec2 v, double scale) {
+	Vec2 result = {
+		.x = v.x * scale,
+		.y = v.y * scale};
+	return result;
+}
+
+bool box2_Intersects(const Box2 x, const Box2 y, Box2 *out_intersection) {
+	// Compute the min and max of the first rectangle on both axes
+	const double r1MinX = dmin(x.lefttop.x, x.lefttop.x + x.size.x);
+	const double r1MaxX = dmax(x.lefttop.x, x.lefttop.x + x.size.x);
+	const double r1MinY = dmin(x.lefttop.y, x.lefttop.x + x.size.x);
+	const double r1MaxY = dmax(x.lefttop.y, x.lefttop.x + x.size.x);
+
+	// Compute the min and max of the second rectangle on both axes
+	const double r2MinX = dmin(y.lefttop.x, y.lefttop.x + y.size.x);
+	const double r2MaxX = dmax(y.lefttop.x, y.lefttop.x + y.size.x);
+	const double r2MinY = dmin(y.lefttop.y, y.lefttop.y + y.size.y);
+	const double r2MaxY = dmax(y.lefttop.y, y.lefttop.y + y.size.y);
+
+	// Compute the intersection boundaries
+	const double interLeft   = dmax(r1MinX, r2MinX);
+	const double interTop    = dmax(r1MinY, r2MinY);
+	const double interRight  = dmin(r1MaxX, r2MaxX);
+	const double interBottom = dmin(r1MaxY, r2MaxY);
+
+	// If the intersection is valid (positive non zero area), then there is an intersection
+	if ((interLeft < interRight) && (interTop < interBottom)) {
+		if (out_intersection) {
+			out_intersection->lefttop.x = interLeft;
+			out_intersection->lefttop.y = interTop;
+			out_intersection->size.x    = interRight - interLeft;
+			out_intersection->size.y    = interBottom - interTop;
+		}
+		return true;
+	} else {
+		return false;
+	}
+}
diff --git a/Types.h b/Types.h
new file mode 100644
index 0000000..91a9890
--- /dev/null
+++ b/Types.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+// A 2d vector of double.
+typedef struct {
+	double x, y;
+} Vec2;
+
+
+Vec2 vec2_Add(Vec2 x, Vec2 y);
+Vec2 vec2_Scale(Vec2 v, double scale);
+
+
+// A 2d box of double.
+typedef struct {
+	Vec2 lefttop;
+	Vec2 size;
+} Box2;
+
+
+// Intersection test.
+bool box2_Intersects(const Box2 x, const Box2 y, Box2 *out_intersection);
+
+
+#ifdef __cplusplus
+}
+#endif