diff --git a/app.c b/app.c
index 7f94aed..8e8ef1d 100644
--- a/app.c
+++ b/app.c
@@ -1,5 +1,6 @@
 
 #include "app.h"
+#include "camera.h"
 #include "entity.h"
 #include "input.h"
 #include "physics.h"
@@ -16,6 +17,7 @@ App *app_NewApp() {
 	app->physics = physics_NewSystem(app);
 	app->player  = player_NewSystem(app);
 	app->entity  = entity_NewSystem(app);
+	app->camera  = camera_NewSystem(app);
 
 	app->wantQuit = false;
 
@@ -59,6 +61,7 @@ void app_DeleteApp(App *app) {
 	entity_DeleteSystem(app->entity);
 	physics_DeleteSystem(app->physics);
 	player_DeleteSystem(app->player);
+	camera_DeleteSystem(app->camera);
 
 	free(app);
 }
@@ -69,4 +72,5 @@ void app_Advance(App *app, Duration deltaTime) {
 	player_Advance(app->player, deltaTime);
 	physics_Advance(app->physics, deltaTime);
 	entity_Advance(app->entity, deltaTime);
+	camera_Advance(app->camera, deltaTime);
 }
diff --git a/app.h b/app.h
index 1d35789..f678ad4 100644
--- a/app.h
+++ b/app.h
@@ -4,6 +4,7 @@
 #include "physics.h"
 #include "player.h"
 #include "input.h"
+#include "camera.h"
 #include "types.h"
 #include "util/vector.h"
 
@@ -17,6 +18,7 @@ typedef struct _App {
 	System_Player  *player;
 	System_Input   *input;
 	System_Entity  *entity;
+	System_Camera  *camera;
 
 	bool wantQuit;
 } App;
diff --git a/app_debug.c b/app_debug.c
index 6b307c2..7be3570 100644
--- a/app_debug.c
+++ b/app_debug.c
@@ -1,5 +1,6 @@
 
 #include "app.h"
+#include "types.h"
 #include "util/vector.h"
 
 #include <stdio.h>
@@ -19,7 +20,7 @@ void app_DebugText(App *app, vector_Vector *vec_string) {
 			buf, sizeof(buf) - 1,
 			"Player:\n"
 			"    Pos: [%.4lf, %.4lf]\n"
-			"    Vec:[%.4lf, %.4lf]\n"
+			"    Vec: [%.4lf, %.4lf]\n"
 			"    OnGround: %s\n"
 			"    JumpCount: %d\n",
 			player->super->position->position.x,
@@ -31,6 +32,17 @@ void app_DebugText(App *app, vector_Vector *vec_string) {
 		PUSH_STRING(buf);
 	}
 
+	Vec2 center = box2_Center(app->camera->cam),
+		 size   = app->camera->cam.size;
+	snprintf(
+		buf, sizeof(buf) - 1,
+		"Camera:\n"
+		"    Center: [%.4lf, %.4lf]\n"
+		"    Size:   [%.4lf, %.4lf]\n",
+		center.x, center.y,
+		size.x, size.y);
+	PUSH_STRING(buf);
+
 	char zero = '\0';
 	vector_Push(vec_string, &zero);
 }
diff --git a/app_render.cpp b/app_render.cpp
index d7f8fc2..726650f 100644
--- a/app_render.cpp
+++ b/app_render.cpp
@@ -1,5 +1,6 @@
 
 #include "app.h"
+#include "camera.h"
 #include "physics.h"
 #include "easyx.h"
 #include "util/tree.h"
@@ -21,7 +22,7 @@ void app_Render(App *app) {
 			else
 				setlinecolor(RGB(255, 255, 0));
 
-			Box2 box = physics_HitboxAbsolute(e->hitbox);
+			Box2 box = camera_TransformBox2(app->camera, physics_HitboxAbsolute(e->hitbox));
 			rectangle(
 				(int)round(box.lefttop.x),
 				(int)round(box.lefttop.y),
diff --git a/camera.c b/camera.c
index bb3d365..265443a 100644
--- a/camera.c
+++ b/camera.c
@@ -1,12 +1,86 @@
 
 #include "camera.h"
 #include "types.h"
+#include "entity.h"
+#include "util/assert.h"
+
+
+static inline double dabs(double x) { return x < 0.0 ? -x : x; }
+static inline double dmin(double x, double y) { return x < y ? x : y; }
 
 
 System_Camera *camera_NewSystem(App *super) {
 	System_Camera *sys = zero_malloc(sizeof(System_Camera));
 	sys->super         = super;
-}
-void camera_DeleteSystem(System_Camera *sys);
 
-void camera_Advance(System_Camera *sys, Duration deltaTime);
+	Box2 default_screen = {
+		.lefttop = {.x = 0.0, .y = 0.0},
+		.size    = {.x = 1280, .y = 720}};
+	sys->cam = sys->screen = default_screen;
+	return sys;
+}
+void camera_DeleteSystem(System_Camera *sys) {
+	free(sys);
+}
+
+
+void camera_AddEntity(System_Camera *sys, Entity *e) {
+	if (e->player) {
+		ASSERT(!sys->player && "Two player entities are added! Did you forget to DeleteEntity for player?");
+		sys->player = e->player;
+	}
+}
+void camera_DeleteEntity(System_Camera *sys, uintptr_t id) {
+	if (sys->player && sys->player->super->id == id)
+		sys->player = NULL;
+}
+
+
+void camera_Advance(System_Camera *sys, Duration deltaTime) {
+	Vec2 tocenter;
+	if (sys->target.size.x > EPS)
+		tocenter = box2_Center(sys->target);
+	else if (sys->player)
+		tocenter = sys->player->super->position->position;
+	else
+		return;
+
+	double speed;
+	if (dabs(sys->speed) < EPS)
+		speed = 4.0;
+	else
+		speed = sys->speed;
+
+	Vec2 oldcenter = box2_Center(sys->cam), oldsize = sys->cam.size;
+	Vec2 newcenter, newsize;
+	Vec2 diff = vec2_Minus(tocenter, oldcenter);
+	if (dabs(diff.x) < EPS && dabs(diff.y) < EPS)
+		newcenter = tocenter;
+	else {
+		Vec2 xdiff = vec2_Scale(diff, dmin(speed * duration_Seconds(deltaTime), 1.0));
+		newcenter  = vec2_Add(oldcenter, xdiff);
+	}
+
+	// TODO size scaling
+	newsize  = oldsize;
+	sys->cam = box2_FromCenter(newcenter, newsize);
+}
+
+
+inline static Vec2 _camera_TransformSize(System_Camera *sys, Vec2 worldSize) {
+	Vec2 result = {
+		.x = worldSize.x / sys->cam.size.x * sys->screen.size.x,
+		.y = worldSize.y / sys->cam.size.y * sys->screen.size.y};
+	return result;
+}
+
+Vec2 camera_TransformVec2(System_Camera *sys, Vec2 world) {
+	Vec2 relative = vec2_Minus(world, sys->cam.lefttop);
+	return vec2_Add(sys->screen.lefttop, _camera_TransformSize(sys, relative));
+}
+Box2 camera_TransformBox2(System_Camera *sys, Box2 world) {
+	Box2 result = {
+		.lefttop = camera_TransformVec2(sys, world.lefttop),
+		.size    = _camera_TransformSize(sys, world.size)};
+	return result;
+}
diff --git a/camera.h b/camera.h
index 8ac8641..f504b1d 100644
--- a/camera.h
+++ b/camera.h
@@ -15,6 +15,7 @@ typedef struct {
 	App              *super;
 	Component_Player *player;
 
+	Box2   screen;      // Screen box, e.g. 1280x720 origin (0,0)
 	Box2   cam, target; // Current & target camera
 	double speed;       // Fraction of distance between cam & target to be covered in 1 sec
 } System_Camera;
@@ -22,8 +23,14 @@ typedef struct {
 System_Camera *camera_NewSystem(App *super);
 void           camera_DeleteSystem(System_Camera *sys);
 
+void camera_AddEntity(System_Camera *sys, Entity *e);
+void camera_DeleteEntity(System_Camera *sys, uintptr_t id);
+
 void camera_Advance(System_Camera *sys, Duration deltaTime);
 
+Vec2 camera_TransformVec2(System_Camera *sys, Vec2 world);
+Box2 camera_TransformBox2(System_Camera *sys, Box2 world);
+
 
 #ifdef __cplusplus
 }
diff --git a/entity.c b/entity.c
index 69e5708..3bcfcba 100644
--- a/entity.c
+++ b/entity.c
@@ -1,6 +1,7 @@
 
 #include "entity.h"
 #include "app.h"
+#include "camera.h"
 #include "physics.h"
 #include "util/assert.h"
 #include "util/tree.h"
@@ -29,6 +30,7 @@ void entity_DeleteSystem(System_Entity *sys) {
 
 		physics_DeleteEntity(sys->super->physics, e->id);
 		player_DeleteEntity(sys->super->player, e->id);
+		camera_DeleteEntity(sys->super->camera, e->id);
 
 		if (e->position)
 			free(e->position);
@@ -67,6 +69,7 @@ Entity *entity_Create(System_Entity *sys, const char *name) {
 void entity_Commit(System_Entity *sys, Entity *e) {
 	physics_AddEntity(sys->super->physics, e);
 	player_AddEntity(sys->super->player, e);
+	camera_AddEntity(sys->super->camera, e);
 }
 
 
@@ -82,6 +85,7 @@ static inline void _entity_Delete(System_Entity *sys, uintptr_t id) {
 
 	physics_DeleteEntity(sys->super->physics, e->id);
 	player_DeleteEntity(sys->super->player, e->id);
+	camera_DeleteEntity(sys->super->camera, e->id);
 
 	if (e->position)
 		free(e->position);
diff --git a/types.c b/types.c
index 8d4ede4..085c0ef 100644
--- a/types.c
+++ b/types.c
@@ -25,6 +25,13 @@ Vec2 vec2_Add(Vec2 x, Vec2 y) {
 	return result;
 }
 
+Vec2 vec2_Minus(Vec2 pos, Vec2 neg) {
+	Vec2 result = {
+		.x = pos.x - neg.x,
+		.y = pos.y - neg.y};
+	return result;
+}
+
 Vec2 vec2_Scale(Vec2 v, double scale) {
 	Vec2 result = {
 		.x = v.x * scale,
@@ -71,6 +78,15 @@ Vec2 box2_Center(Box2 box) {
 		box.lefttop.y + box.size.y / 2.0);
 }
 
+Box2 box2_FromCenter(Vec2 center, Vec2 size) {
+	Box2 box = {
+		.size    = size,
+		.lefttop = {
+			.x = center.x - size.x / 2.0,
+			.y = center.y - size.y / 2.0}};
+	return box;
+}
+
 Box2 box2_Offset(Box2 box, Vec2 offset) {
 	box.lefttop = vec2_Add(box.lefttop, offset);
 	return box;
diff --git a/types.h b/types.h
index 0425e87..a9ca92b 100644
--- a/types.h
+++ b/types.h
@@ -29,6 +29,7 @@ static inline Vec2 vec2(double x, double y) {
 }
 
 Vec2 vec2_Add(Vec2 x, Vec2 y);
+Vec2 vec2_Minus(Vec2 pos, Vec2 neg);
 Vec2 vec2_Scale(Vec2 v, double scale);
 
 
@@ -43,6 +44,7 @@ typedef struct {
 bool box2_Intersects(const Box2 x, const Box2 y, Box2 *out_intersection);
 
 Vec2 box2_Center(Box2 box);
+Box2 box2_FromCenter(Vec2 center, Vec2 size);
 
 Box2 box2_Offset(Box2 box, Vec2 offset);
 Box2 box2_OffsetX(Box2 box, double offsetX);