diff --git a/src/compat/SDL/SDL.h b/src/compat/SDL/SDL.h
new file mode 100644
index 0000000..fb1fa2b
--- /dev/null
+++ b/src/compat/SDL/SDL.h
@@ -0,0 +1,3 @@
+/* SDL/SDL.h for the fredygames.com browser build of Zatacka X: the SDL 2 header, same API.
+ * Copyright (C) 2026 FredyGames. GNU GPL version 3 or later, like Zatacka X. */
+#include <SDL.h>
diff --git a/src/compat/SDL/SDL_image.h b/src/compat/SDL/SDL_image.h
new file mode 100644
index 0000000..aa696ff
--- /dev/null
+++ b/src/compat/SDL/SDL_image.h
@@ -0,0 +1,3 @@
+/* SDL/SDL_image.h for the fredygames.com browser build of Zatacka X: the SDL 2 header, same API.
+ * Copyright (C) 2026 FredyGames. GNU GPL version 3 or later, like Zatacka X. */
+#include <SDL_image.h>
diff --git a/src/compat/SDL/SDL_mixer.h b/src/compat/SDL/SDL_mixer.h
new file mode 100644
index 0000000..565ec23
--- /dev/null
+++ b/src/compat/SDL/SDL_mixer.h
@@ -0,0 +1,3 @@
+/* SDL/SDL_mixer.h for the fredygames.com browser build of Zatacka X: the SDL 2 header, same API.
+ * Copyright (C) 2026 FredyGames. GNU GPL version 3 or later, like Zatacka X. */
+#include <SDL_mixer.h>
diff --git a/src/compat/SDL/SDL_stdinc.h b/src/compat/SDL/SDL_stdinc.h
new file mode 100644
index 0000000..fa52ade
--- /dev/null
+++ b/src/compat/SDL/SDL_stdinc.h
@@ -0,0 +1,3 @@
+/* SDL/SDL_stdinc.h for the fredygames.com browser build of Zatacka X: the SDL 2 header, same API.
+ * Copyright (C) 2026 FredyGames. GNU GPL version 3 or later, like Zatacka X. */
+#include <SDL_stdinc.h>
diff --git a/src/compat/SDL/SDL_ttf.h b/src/compat/SDL/SDL_ttf.h
new file mode 100644
index 0000000..bbd8395
--- /dev/null
+++ b/src/compat/SDL/SDL_ttf.h
@@ -0,0 +1,3 @@
+/* SDL/SDL_ttf.h for the fredygames.com browser build of Zatacka X: the SDL 2 header, same API.
+ * Copyright (C) 2026 FredyGames. GNU GPL version 3 or later, like Zatacka X. */
+#include <SDL_ttf.h>
diff --git a/src/zatackax.c b/src/zatackax.c
index dcc9393..62f7386 100755
--- a/src/zatackax.c
+++ b/src/zatackax.c
@@ -2066,6 +2066,14 @@ void exitGame(int status)
     exit(status);
 }
 
+#ifdef __EMSCRIPTEN__
+/* Called by the page when the tab is hidden or closed. */
+void fredygames_save(void)
+{
+    saveSettings();
+}
+#endif
+
 int main(void)
 {
     static Uint32 prevtime = 0;
@@ -2198,17 +2206,7 @@ int main(void)
             else if (event.type == SDL_QUIT) {
                 exitGame(0);
             }
-            else if (event.type == SDL_VIDEORESIZE) {
-                WINDOW_W = event.resize.w;
-                WINDOW_H = event.resize.h;
 
-                if (!initScreen()) {
-                    return 1;
-                }
-
-                initHitMap(WINDOW_W, WINDOW_H);
-                refreshGameScreen();
-            }
         }
         if (!screenFreeze) {
             Uint32 timenow = SDL_GetTicks();
@@ -2218,11 +2216,33 @@ int main(void)
             if (delta < 1000/FPS_CAP) {
                 SDL_Delay(1000/FPS_CAP - delta);
             }
+#ifdef __EMSCRIPTEN__
+            else {
+                /* Late frame: still gives the browser a turn to show it. */
+                SDL_Delay(1);
+            }
+#endif
 
             if (curScene->logicFunc()) {
                 curScene->displayFunc();
             }
         }
+#ifdef __EMSCRIPTEN__
+        else {
+            /* Frozen end-of-round screen: wait for a key without hogging the page. */
+            SDL_Delay(10);
+        }
+
+        /* Browser build: keeps the settings in the browser every 30 seconds. */
+        {
+            static Uint32 lastSave = 0;
+            Uint32 now = SDL_GetTicks();
+            if (now - lastSave > 30000) {
+                lastSave = now;
+                saveSettings();
+            }
+        }
+#endif
     }
 
     return 0;
diff --git a/src/ztksdl12.c b/src/ztksdl12.c
new file mode 100644
index 0000000..001d4fe
--- /dev/null
+++ b/src/ztksdl12.c
@@ -0,0 +1,168 @@
+/*
+ * ztksdl12.c: see ztksdl12.h. The game draws on the surface of SDL_SetVideoMode (here a 32-bit surface in
+ * memory, as the game asks for); each SDL_Flip uploads it to a streaming texture and shows it.
+ * Copyright (C) 2026 FredyGames. Distributed under the GNU GPL version 3 or later, like the game.
+ */
+#include "ztksdl12.h"
+
+#undef SDL_SetVideoMode
+#undef SDL_FreeSurface
+#undef SDL_SetColorKey
+#undef SDL_PollEvent
+#undef SDL_Delay
+#undef SDLK_UNKNOWN
+#undef SDLK_BACKSPACE
+#undef SDLK_TAB
+#undef SDLK_CLEAR
+#undef SDLK_RETURN
+#undef SDLK_PAUSE
+#undef SDLK_ESCAPE
+#undef SDLK_DELETE
+#undef SDLK_UP
+#undef SDLK_DOWN
+#undef SDLK_RIGHT
+#undef SDLK_LEFT
+
+static SDL_Window *window = NULL;
+static SDL_Renderer *renderer = NULL;
+static SDL_Texture *texture = NULL;
+static SDL_Surface *screen = NULL;
+
+SDL_Surface *ztk_SetVideoMode(int width, int height, int bpp, Uint32 flags)
+{
+	(void)bpp; (void)flags;
+	if (window == NULL) {
+		window = SDL_CreateWindow("Zatacka X", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, 0);
+		if (window == NULL)
+			return NULL;
+		renderer = SDL_CreateRenderer(window, -1, 0);
+		if (renderer == NULL)
+			return NULL;
+	}
+	if (texture != NULL)
+		SDL_DestroyTexture(texture);
+	if (screen != NULL)
+		SDL_FreeSurface(screen);
+	SDL_SetWindowSize(window, width, height);
+	texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB888, SDL_TEXTUREACCESS_STREAMING, width, height);
+	screen = SDL_CreateRGBSurfaceWithFormat(0, width, height, 32, SDL_PIXELFORMAT_RGB888);
+	return screen;
+}
+
+int ztk_Flip(SDL_Surface *surface)
+{
+	if (surface != screen || texture == NULL)
+		return -1;
+	SDL_UpdateTexture(texture, NULL, screen->pixels, screen->pitch);
+	SDL_RenderClear(renderer);
+	SDL_RenderCopy(renderer, texture, NULL, NULL);
+	SDL_RenderPresent(renderer);
+	return 0;
+}
+
+/* SDL 1.2 let the program free the display surface (the next SDL_SetVideoMode makes a new one): here the
+   surface belongs to the shim, so freeing it does nothing. */
+void ztk_FreeSurface(SDL_Surface *surface)
+{
+	if (surface != NULL && surface != screen)
+		SDL_FreeSurface(surface);
+}
+
+SDL_Surface *ztk_DisplayFormatAlpha(SDL_Surface *surface)
+{
+	return SDL_ConvertSurfaceFormat(surface, SDL_PIXELFORMAT_ARGB8888, 0);
+}
+
+/* SDL 1.2 per-surface alpha: SDL_SRCALPHA turns blending on with that alpha, no flag turns it off. */
+int ztk_SetAlpha(SDL_Surface *surface, Uint32 flags, Uint8 alpha)
+{
+	if (flags & SDL_SRCALPHA) {
+		SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_BLEND);
+		return SDL_SetSurfaceAlphaMod(surface, alpha);
+	}
+	SDL_SetSurfaceBlendMode(surface, surface->format->Amask ? SDL_BLENDMODE_BLEND : SDL_BLENDMODE_NONE);
+	return SDL_SetSurfaceAlphaMod(surface, 255);
+}
+
+int ztk_SetColorKey(SDL_Surface *surface, Uint32 flags, Uint32 key)
+{
+	return SDL_SetColorKey(surface, (flags & SDL_SRCCOLORKEY) ? SDL_TRUE : SDL_FALSE, key);
+}
+
+/* SDL 2 key code -> SDL 1.2 key symbol (0 when there is none). The SDL 2 codes of keys that are not
+   characters are the scancode with bit 30 set. */
+static int key12(Sint32 k)
+{
+	if (k >= 0 && k < 128)
+		return k;
+	if (k & 0x40000000) {
+		int sc = k & 0xFFFF;
+		if (sc >= 58 && sc <= 69)		/* F1-F12 */
+			return 282 + (sc - 58);
+		if (sc >= 104 && sc <= 106)		/* F13-F15 */
+			return 294 + (sc - 104);
+		if (sc >= 89 && sc <= 97)		/* keypad 1-9 */
+			return 257 + (sc - 89);
+		switch (sc) {
+		case 98: return 256;			/* keypad 0 */
+		case 99: return 266;			/* keypad period */
+		case 84: return 267;			/* keypad divide */
+		case 85: return 268;			/* keypad multiply */
+		case 86: return 269;			/* keypad minus */
+		case 87: return 270;			/* keypad plus */
+		case 88: return 271;			/* keypad enter */
+		case 103: return 272;			/* keypad equals */
+		case 82: return 273;			/* up */
+		case 81: return 274;			/* down */
+		case 79: return 275;			/* right */
+		case 80: return 276;			/* left */
+		case 73: return 277;			/* insert */
+		case 74: return 278;			/* home */
+		case 77: return 279;			/* end */
+		case 75: return 280;			/* page up */
+		case 78: return 281;			/* page down */
+		case 83: return 300;			/* num lock */
+		case 57: return 301;			/* caps lock */
+		case 71: return 302;			/* scroll lock */
+		case 229: return 303;			/* right shift */
+		case 225: return 304;			/* left shift */
+		case 228: return 305;			/* right ctrl */
+		case 224: return 306;			/* left ctrl */
+		case 230: return 307;			/* right alt */
+		case 226: return 308;			/* left alt */
+		case 231: return 312;			/* right super */
+		case 227: return 311;			/* left super */
+		case 72: return 19;			/* pause */
+		case 70: return 316;			/* print screen */
+		case 118: return 319;			/* menu */
+		}
+	}
+	return 0;
+}
+
+/* SDL 1.2 had no key repeat unless asked for; SDL 2 always has it. Repeats are dropped here, and the key
+   symbols of the events are the SDL 1.2 ones. */
+int ztk_PollEvent(SDL_Event *event)
+{
+	while (SDL_PollEvent(event)) {
+		if (event->type == SDL_KEYDOWN || event->type == SDL_KEYUP) {
+			if (event->type == SDL_KEYDOWN && event->key.repeat)
+				continue;
+			event->key.keysym.sym = key12(event->key.keysym.sym);
+		}
+		return 1;
+	}
+	return 0;
+}
+
+void ztk_WM_SetCaption(const char *title, const char *icon)
+{
+	(void)icon;
+	if (window != NULL && title != NULL)
+		SDL_SetWindowTitle(window, title);
+}
+
+void ztk_WM_SetIcon(SDL_Surface *icon, Uint8 *mask)
+{
+	(void)icon; (void)mask;
+}
diff --git a/src/ztksdl12.h b/src/ztksdl12.h
new file mode 100644
index 0000000..2429063
--- /dev/null
+++ b/src/ztksdl12.h
@@ -0,0 +1,132 @@
+/*
+ * ztksdl12.h: the part of the SDL 1.2 API that Zatacka X uses, on top of SDL 2, for the fredygames.com
+ * browser build (Emscripten). Included before every source file (-include).
+ * Written for that build.
+ * Copyright (C) 2026 FredyGames. Distributed under the GNU GPL version 3 or later, like the game.
+ */
+#ifndef ZTKSDL12_H
+#define ZTKSDL12_H
+
+#include <SDL.h>
+#include <emscripten.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef int SDLKey;
+
+#define SDL_SWSURFACE 0x00000000
+#define SDL_HWSURFACE 0x00000001
+#define SDL_RESIZABLE 0x00000010
+#define SDL_FULLSCREEN 0x80000000
+#define SDL_SRCCOLORKEY 0x00001000
+#define SDL_SRCALPHA 0x00010000
+/* SDL 2 has no resize event of this kind: the page keeps the window at one size. */
+#define SDL_VIDEORESIZE 0x7ffe
+#undef SDL_INIT_EVERYTHING
+#define SDL_INIT_EVERYTHING (SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_JOYSTICK | SDL_INIT_TIMER)
+
+SDL_Surface *ztk_SetVideoMode(int width, int height, int bpp, Uint32 flags);
+int ztk_Flip(SDL_Surface *screen);
+void ztk_FreeSurface(SDL_Surface *surface);
+SDL_Surface *ztk_DisplayFormatAlpha(SDL_Surface *surface);
+int ztk_SetAlpha(SDL_Surface *surface, Uint32 flags, Uint8 alpha);
+int ztk_SetColorKey(SDL_Surface *surface, Uint32 flags, Uint32 key);
+int ztk_PollEvent(SDL_Event *event);
+void ztk_WM_SetCaption(const char *title, const char *icon);
+void ztk_WM_SetIcon(SDL_Surface *icon, Uint8 *mask);
+
+#ifdef __cplusplus
+}
+#endif
+
+#define SDL_SetVideoMode ztk_SetVideoMode
+#define SDL_Flip ztk_Flip
+#undef SDL_FreeSurface
+#define SDL_FreeSurface ztk_FreeSurface
+#define SDL_DisplayFormatAlpha ztk_DisplayFormatAlpha
+#define SDL_SetAlpha ztk_SetAlpha
+#define SDL_SetColorKey ztk_SetColorKey
+#define SDL_PollEvent ztk_PollEvent
+#define SDL_WM_SetCaption ztk_WM_SetCaption
+#define SDL_WM_SetIcon ztk_WM_SetIcon
+/* The loop waits for the next frame with SDL_Delay: here that hands the page back to the browser (Asyncify). */
+#undef SDL_Delay
+#define SDL_Delay(ms) emscripten_sleep(ms)
+
+/* The game indexes arrays with SDL 1.2 key symbols (322 of them): the key names have the SDL 1.2 values, and
+   ztk_PollEvent converts the SDL 2 key codes of each event to them. */
+#undef SDLK_UNKNOWN
+#define SDLK_UNKNOWN 0
+#undef SDLK_BACKSPACE
+#define SDLK_BACKSPACE 8
+#undef SDLK_TAB
+#define SDLK_TAB 9
+#undef SDLK_CLEAR
+#define SDLK_CLEAR 12
+#undef SDLK_RETURN
+#define SDLK_RETURN 13
+#undef SDLK_PAUSE
+#define SDLK_PAUSE 19
+#undef SDLK_ESCAPE
+#define SDLK_ESCAPE 27
+#undef SDLK_DELETE
+#define SDLK_DELETE 127
+#undef SDLK_UP
+#define SDLK_UP 273
+#undef SDLK_DOWN
+#define SDLK_DOWN 274
+#undef SDLK_RIGHT
+#define SDLK_RIGHT 275
+#undef SDLK_LEFT
+#define SDLK_LEFT 276
+#undef SDLK_INSERT
+#define SDLK_INSERT 277
+#undef SDLK_HOME
+#define SDLK_HOME 278
+#undef SDLK_END
+#define SDLK_END 279
+#undef SDLK_PAGEUP
+#define SDLK_PAGEUP 280
+#undef SDLK_PAGEDOWN
+#define SDLK_PAGEDOWN 281
+#undef SDLK_F1
+#define SDLK_F1 282
+#undef SDLK_F2
+#define SDLK_F2 283
+#undef SDLK_F3
+#define SDLK_F3 284
+#undef SDLK_F15
+#define SDLK_F15 296
+#undef SDLK_SCROLLOCK
+#define SDLK_SCROLLOCK 302
+#undef SDLK_RSHIFT
+#define SDLK_RSHIFT 303
+#undef SDLK_LSHIFT
+#define SDLK_LSHIFT 304
+#undef SDLK_RCTRL
+#define SDLK_RCTRL 305
+#undef SDLK_LCTRL
+#define SDLK_LCTRL 306
+#undef SDLK_RALT
+#define SDLK_RALT 307
+#undef SDLK_LALT
+#define SDLK_LALT 308
+#undef SDLK_RSUPER
+#define SDLK_RSUPER 312
+#undef SDLK_LSUPER
+#define SDLK_LSUPER 311
+#undef SDLK_MODE
+#define SDLK_MODE 313
+#undef SDLK_COMPOSE
+#define SDLK_COMPOSE 314
+#undef SDLK_PRINT
+#define SDLK_PRINT 316
+#undef SDLK_MENU
+#define SDLK_MENU 319
+#define SDLK_WORLD_69 229
+#define SDLK_WORLD_70 230
+#define SDLK_WORLD_88 248
+
+#endif