diff --git a/app.c b/app.c
index 10af39b..58a06f8 100644
--- a/app.c
+++ b/app.c
@@ -17,7 +17,7 @@
 App *app_NewApp() {
 	render_LoadBundle("bundles.txt");
 
-	App *app = malloc(sizeof(App));
+	App *app = zero_malloc(sizeof(App));
 
 	app->input    = input_NewSystem(app);
 	app->physics  = physics_NewSystem(app);
@@ -26,7 +26,8 @@ App *app_NewApp() {
 	app->camera   = camera_NewSystem(app);
 	app->particle = particle_NewSystem(app);
 
-	app->wantQuit = false;
+	app->switch_level = NULL;
+	app->wantQuit     = false;
 
 
 	Entity *player = entity_Create(app->entity, "player");
@@ -104,6 +105,13 @@ void app_DeleteApp(App *app) {
 
 
 void app_Advance(App *app, Duration deltaTime) {
+	// Limit deltaTime to 20ms (1/50 second)
+	if (deltaTime.microseconds > 20000)
+		deltaTime.microseconds = 20000;
+
+	if (app->switch_level != NULL)
+		_app_SwitchLevel(app);
+
 	particle_Advance(app->particle, deltaTime);
 	input_Advance(app->input);
 	player_Advance(app->player, deltaTime);
diff --git a/app.h b/app.h
index f1de50b..c26eac6 100644
--- a/app.h
+++ b/app.h
@@ -22,7 +22,8 @@ typedef struct _App {
 	System_Camera   *camera;
 	System_Particle *particle;
 
-	bool wantQuit;
+	char *switch_level;
+	bool  wantQuit;
 } App;
 
 App *app_NewApp();
@@ -33,6 +34,10 @@ void app_Render(App *app);
 
 void app_DebugText(App *app, vector_Vector *vec_string);
 
+// Trigger the app to reload all entities before next frame update.
+void app_QueueLoadLevel(App *app, const char *level_name);
+void _app_SwitchLevel(App *app);
+
 
 #ifdef __cplusplus
 }
diff --git a/app_file.c b/app_file.c
new file mode 100644
index 0000000..c18e57a
--- /dev/null
+++ b/app_file.c
@@ -0,0 +1,16 @@
+
+#include <stdio.h>
+#include "app.h"
+#include "types.h"
+
+
+void app_QueueLoadLevel(App *app, const char *level_name) {
+	if (app->switch_level != NULL) {
+		WARN("previous switch_level \"%s\" not processed; purged", app->switch_level);
+		free(app->switch_level);
+	}
+	app->switch_level = copy_malloc(level_name);
+}
+
+void _app_SwitchLevel(App *app) {
+}