The Legend of Edgar 1.38 (94d76eb) for fredygames.com (GPL-2.0-or-later, like the game). Every change is
active only when building with Emscripten (__EMSCRIPTEN__):

- init.c: the game never goes fullscreen (the page has its own fullscreen button), so the option and the
  fullscreen key do nothing;
- draw.c: delay() hands the turn back to the browser (emscripten_sleep(0)) when a frame is late; the build
  uses Asyncify and SDL_Delay already yields otherwise;
- main.c: fredygames_save(), which the page calls when the tab is hidden or closed: the settings
  (volumes, controls) are only written when the game exits;
- system/error.c: the error screen is drawn once and the runtime stops (it cannot sleep in a loop);
- system/load_save.c: the browser has no user database, so the saves directory is
  /home/web_user/.parallelrealities (the page keeps it in IndexedDB).

diff -ruN a/src/draw.c b/src/draw.c
--- a/src/draw.c	2026-02-09 19:38:22.000000000 -0300
+++ b/src/draw.c	2026-11-01 19:23:13.063741886 -0300
@@ -19,6 +19,10 @@
 
 #include "headers.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
 #include "credits.h"
 #include "dialog.h"
 #include "entity.h"
@@ -231,6 +235,10 @@
 
 	if (frameLimit < ticks)
 	{
+#ifdef __EMSCRIPTEN__
+		/* Late frame: still give the browser a turn (the build uses Asyncify) */
+		emscripten_sleep(0);
+#endif
 		return;
 	}
 
diff -ruN a/src/init.c b/src/init.c
--- a/src/init.c	2026-02-09 19:38:22.000000000 -0300
+++ b/src/init.c	2026-11-01 19:22:57.318568550 -0300
@@ -29,6 +29,10 @@
 #include "system/record.h"
 #include "system/resources.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
 extern Game game;
 
 void init(char *title, int joystickNum)
@@ -66,6 +70,11 @@
 
 	loadConfig();
 
+#ifdef __EMSCRIPTEN__
+	/* The page has its own fullscreen button */
+	game.fullscreen = FALSE;
+#endif
+
 	if (game.fullscreen == TRUE)
 	{
 		windowFlags |= SDL_WINDOW_FULLSCREEN;
@@ -148,6 +157,9 @@
 
 void toggleFullScreen()
 {
+#ifdef __EMSCRIPTEN__
+	return;
+#endif
 	long fullScreen = SDL_GetWindowFlags(game.window) & SDL_WINDOW_FULLSCREEN;
 
 	fullScreen ^= SDL_WINDOW_FULLSCREEN;
diff -ruN a/src/main.c b/src/main.c
--- a/src/main.c	2026-02-09 19:38:22.000000000 -0300
+++ b/src/main.c	2026-11-01 20:08:53.755376406 -0300
@@ -45,6 +45,17 @@
 #include "system/resources.h"
 #include "title.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+
+/* Called by the page when the tab is hidden or closed: the settings (volumes, controls) are only
+   written when the game exits */
+EMSCRIPTEN_KEEPALIVE void fredygames_save(void)
+{
+	saveConfig();
+}
+#endif
+
 Input input, menuInput;
 Entity *self;
 Game game;
diff -ruN a/src/system/error.c b/src/system/error.c
--- a/src/system/error.c	2026-02-09 19:38:22.000000000 -0300
+++ b/src/system/error.c	2026-11-01 19:24:50.618037207 -0300
@@ -19,6 +19,10 @@
 
 #include "../headers.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
 #include "../audio/music.h"
 #include "../graphics/font.h"
 #include "../graphics/graphics.h"
@@ -144,6 +148,14 @@
 
 static void drawError()
 {
+#ifdef __EMSCRIPTEN__
+	/* Show the error screen once and stop: the page keeps the last frame (Asyncify cannot sleep here) */
+	clearScreen(0, 0, 0);
+	SDL_RenderCopy(game.renderer, game.tempSurface->texture, NULL, NULL);
+	SDL_RenderPresent(game.renderer);
+	emscripten_exit_with_live_runtime();
+#endif
+
 	do
 	{
 		getInput(game.gameType);
diff -ruN a/src/system/load_save.c b/src/system/load_save.c
--- a/src/system/load_save.c	2026-02-09 19:38:22.000000000 -0300
+++ b/src/system/load_save.c	2026-11-01 20:00:52.960731185 -0300
@@ -67,6 +67,11 @@
 		#endif
 		struct passwd *pass;
 
+#ifdef __EMSCRIPTEN__
+		/* The browser has no user database: the page mounts the saves under this directory */
+		(void)pass;
+		userHome = "/home/web_user";
+#else
 		pass = getpwuid(geteuid());
 
 		if (pass == NULL)
@@ -77,6 +82,7 @@
 		}
 
 		userHome = pass->pw_dir;
+#endif
 
 		#if MACOS == 1
 		SNPRINTF(dir, sizeof(dir), "%s/Library/Application Support", userHome);