diff --git a/JLib/JLib/Graphics/JImage.cpp b/JLib/JLib/Graphics/JImage.cpp
index 99a8d91..79ebef5 100644
--- a/JLib/JLib/Graphics/JImage.cpp
+++ b/JLib/JLib/Graphics/JImage.cpp
@@ -317,6 +317,11 @@ u32 JImage::Load(JRW &f)
 u32 JImage::Save(JRW &f)
 {
   u32 sz = Size();
+#ifdef __EMSCRIPTEN__
+  u32 colorkey = hc_ColorKey(surface);
+#else
+  u32 colorkey = surface->format->colorkey;
+#endif
   if (f.WriteLE32(&surface->w) &&
       f.WriteLE32(&surface->h) &&
       f.Write8(&surface->format->BitsPerPixel) &&
@@ -324,7 +329,7 @@ u32 JImage::Save(JRW &f)
       f.WriteLE32(&surface->format->Gmask) &&
       f.WriteLE32(&surface->format->Bmask) &&
       f.WriteLE32(&surface->format->Amask) &&
-      f.WriteLE32(&surface->format->colorkey) &&
+      f.WriteLE32(&colorkey) &&
       f.WriteLE32(&sz))
   {
     if (0 == Lock())
@@ -400,7 +405,7 @@ JImage * JImage::Scale(float xp, float yp)
 			{
 				for (float nx = nx0; nx < nx0 + dx; ++nx)
 				{
-					SDL_GetRGBA(GetPixel((s32)nx, (s32)ny), surface->format, &samp.r, &samp.g, &samp.b, &samp.unused);
+					SDL_GetRGBA(GetPixel((s32)nx, (s32)ny), surface->format, &samp.r, &samp.g, &samp.b, &samp.a);
 					
 					// Averigua la cuota de participación del pixel.
 					// Para ello vemos el cociente entre la superficie de pixel original en la nueva imagen
@@ -417,7 +422,7 @@ JImage * JImage::Scale(float xp, float yp)
 					rAccum += float(samp.r) * ratio;
 					gAccum += float(samp.g) * ratio;
 					bAccum += float(samp.b) * ratio;
-					aAccum += float(samp.unused) * ratio;
+					aAccum += float(samp.a) * ratio;
 				}
 			}
 
@@ -497,7 +502,12 @@ JString JImage::DumpFromSurface(SDL_Surface *s)
 	JString s1, s2, s3, s4, s5, s6;
 	SDL_PixelFormat *fmt = s->format;
 
-	s1.Format("%dx%d@%d COLOR_KEY: %08x SURFACE_ALPHA: %d\n", s->w, s->h, fmt->BitsPerPixel, fmt->colorkey, fmt->alpha);
+	s1.Format("%dx%d@%d COLOR_KEY: %08x SURFACE_ALPHA: %d\n", s->w, s->h, fmt->BitsPerPixel,
+#ifdef __EMSCRIPTEN__
+	          hc_ColorKey(s), hc_SurfaceAlpha(s));
+#else
+	          fmt->colorkey, fmt->alpha);
+#endif
 	s2.Format("pitch: %d clip_rect: x%d y%d w%d h%d pixels: %p\n", s->pitch, s->clip_rect.x, s->clip_rect.y, s->clip_rect.w, s->clip_rect.h, s->pixels);
 	s3.Format("RGBAmask: R: 0x%08x G: 0x%08x B: 0x%08x A: 0x%08x\n", fmt->Rmask, fmt->Gmask, fmt->Bmask, fmt->Amask);
 	s4.Format("RGBAshift: R: 0x%08x G: 0x%08x B: 0x%08x A: 0x%08x\n", fmt->Rshift, fmt->Gshift, fmt->Bshift, fmt->Ashift);
diff --git a/JLib/JLib/Graphics/JImage.h b/JLib/JLib/Graphics/JImage.h
index 5e4d433..b78fd54 100644
--- a/JLib/JLib/Graphics/JImage.h
+++ b/JLib/JLib/Graphics/JImage.h
@@ -159,7 +159,11 @@ public:
   /** Devuelve el alfa asociado a la superficie
    * @return Alfa de la superficie.
    */
+  #ifdef __EMSCRIPTEN__
+  u8 Alpha() {return hc_SurfaceAlpha(surface);}
+#else
   u8 Alpha() {return surface->format->alpha;}
+#endif
 	
   /** Establece el color transparente y habilita el uso de color transparente en la superficie.
    * @param  key Color transparente.
@@ -170,7 +174,11 @@ public:
 	/** Devuelve el color transparente
    * @return Color transparente.
    */
+  #ifdef __EMSCRIPTEN__
+  u32 ColorKey() {return hc_ColorKey(surface);}
+#else
   u32 ColorKey() {return surface->format->colorkey;}
+#endif
 
   /** Pega el contenido de una imagen en esta. No comprueba que 
    * no se sobrepasen los límites de la imagen.
diff --git a/JLib/JLib/Util/JApp.cpp b/JLib/JLib/Util/JApp.cpp
index f130faa..e2d9dea 100644
--- a/JLib/JLib/Util/JApp.cpp
+++ b/JLib/JLib/Util/JApp.cpp
@@ -28,6 +28,9 @@
  */
 
 #include <JLib/Util/JApp.h>
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
 
 JApp * JApp::thisApp = 0;
 
@@ -141,6 +144,7 @@ bool JApp::UpdateEvents()
   {
     switch(e.type)
     {
+#ifndef __EMSCRIPTEN__
       case SDL_ACTIVEEVENT:
 				// Pasamos a estado de pausa
 				switch (e.active.state)
@@ -168,6 +172,7 @@ bool JApp::UpdateEvents()
 				}
         break;
 
+#endif
       case SDL_KEYDOWN:
 				
 				// Actualiza el estado del teclado
@@ -294,6 +299,7 @@ bool JApp::UpdateEvents()
         }
         break;
 
+#ifndef __EMSCRIPTEN__
       case SDL_VIDEORESIZE:
 
 				if (__OnResize)
@@ -313,6 +319,7 @@ bool JApp::UpdateEvents()
         }
         break;
 
+#endif
       case SDL_USEREVENT:
         if (__OnUser)
         {
@@ -349,6 +356,13 @@ s32 JApp::MainLoop()
 					printf("Error updating the app.\n");
 				}
 			}
+#ifdef __EMSCRIPTEN__
+			else
+			{
+				// gives the browser a turn while waiting for the next frame
+				emscripten_sleep(1);
+			}
+#endif
 		}
 		else
 		{
@@ -541,8 +555,10 @@ void JApp::DumpVideoInfo()
 	fprintf(stdout, 
 					"     RGBAloss: R: 0x%08x G: 0x%08x B: 0x%08x A: 0x%08x\n", 
 					vi->vfmt->Rloss, vi->vfmt->Gloss, vi->vfmt->Bloss, vi->vfmt->Aloss);
+#ifndef __EMSCRIPTEN__
 	fprintf(stdout, "     ColorKey: 0x%08x\n", vi->vfmt->colorkey);
 	fprintf(stdout, "        Alpha: 0x%02x\n", vi->vfmt->alpha);
+#endif
 }
 
 void JApp::Icon(const char *filename)
diff --git a/JLib/JLib/Util/JRW.h b/JLib/JLib/Util/JRW.h
index 43c44e2..13af3fd 100644
--- a/JLib/JLib/Util/JRW.h
+++ b/JLib/JLib/Util/JRW.h
@@ -71,7 +71,7 @@ class JRW : public JObject
 	{
     Destroy();
 		
-		return (0 != (rwops = SDL_RWFromFP(fp, autoclose)));
+		return (0 != (rwops = SDL_RWFromFP(fp, autoclose ? SDL_TRUE : SDL_FALSE)));
 	}
 
 	/** Creates (and destroys any existing) SDL_RWops structure to access a memory block.
diff --git a/JLib/JLib/Util/JTextFile.cpp b/JLib/JLib/Util/JTextFile.cpp
index 7689b24..feba4d1 100644
--- a/JLib/JLib/Util/JTextFile.cpp
+++ b/JLib/JLib/Util/JTextFile.cpp
@@ -349,7 +349,12 @@ u32 JTextFile::Printf(const s8 *fmt, ... )
   vsprintf(str, fmt, vlist);
   va_end(vlist);
 
+#ifdef __EMSCRIPTEN__
+  // musl's fputs returns 0 on success, which the callers take as an error
+  return (fputs(str, file) >= 0) ? 1 : 0;
+#else
   return(fputs(str, file));
+#endif
 }
 
 // Lectura tipo scanf
diff --git a/JLib/JLib/Util/JUtil.cpp b/JLib/JLib/Util/JUtil.cpp
index adf1ef3..f8b8a1f 100644
--- a/JLib/JLib/Util/JUtil.cpp
+++ b/JLib/JLib/Util/JUtil.cpp
@@ -206,7 +206,13 @@ void JDumpImage(JImage *img, s32 n)
 
 	fprintf(stderr, 
 					"%dx%d@%d CKEY: %08x ALPHA: %d SRCALPHA: %s SRCCOLORKEY: %s RLE: %s\n", 
-					s->w, s->h, fmt->BitsPerPixel, fmt->colorkey, fmt->alpha, 
+					s->w, s->h, fmt->BitsPerPixel,
+#ifdef __EMSCRIPTEN__
+					hc_ColorKey(s), hc_SurfaceAlpha(s),
+#else
+					fmt->colorkey, fmt->alpha,
+#endif
+					
 					s->flags & SDL_SRCALPHA ? "yes" : "no", 
 					s->flags & SDL_SRCCOLORKEY ? "yes" : "no",
 					s->flags & SDL_RLEACCEL ? "yes" : "no");
@@ -242,7 +248,11 @@ void JDumpImage(JImage *img, s32 n)
 		{
 			for (s32 i = 0; count <= n && i < s->w; ++i)
 			{
+				#ifdef __EMSCRIPTEN__
+				if (img->GetPixel(i, j) != hc_ColorKey(s))
+#else
 				if (img->GetPixel(i, j) != fmt->colorkey)
+#endif
 				{
 					fprintf(stderr, "%08x ", img->GetPixel(i, j));
 
diff --git a/res/playlist.txt b/res/playlist.txt
index 252a04e..a6b55f4 100644
--- a/res/playlist.txt
+++ b/res/playlist.txt
@@ -1,2 +1 @@
 holotzcastle
-milanb
diff --git a/src/HolotzCastle.cpp b/src/HolotzCastle.cpp
index f599bed..253b58e 100644
--- a/src/HolotzCastle.cpp
+++ b/src/HolotzCastle.cpp
@@ -366,6 +366,15 @@ bool HCApp::InitMenu()
 	if (f.ReadLine(str)) it->AddNodeGo(new JTextMenuEntry(str, &OnHelp, 0)); else return false;              // Help
 	if (f.ReadLine(str)) it->AddNodeGo(new JTextMenuEntry(str, 0, 0)); else return false;                    // Options
 	{
+#ifdef __EMSCRIPTEN__
+		// fredygames.com: no video options (the page scales a fixed 640x480 screen and has its own
+		// fullscreen button); their seven lines of menu.txt are skipped
+		for (s32 skip = 0; skip < 7; ++skip)
+		{
+			if (!f.ReadLine(str)) return false;
+		}
+		if (f.ReadLine(str)) it->AddBranchGo(new JTextMenuEntry(str, 0, 0)); else return false;                //  Sound
+#else
 		if (f.ReadLine(str)) it->AddBranchGo(new JTextMenuEntry(str, 0, 0)); else return false;                //  Video
 		{
 			if (f.ReadLine(str)) it->AddBranchGo(new JTextMenuEntry(str, 0, 0)); else return false;              //   Size
@@ -414,6 +423,7 @@ bool HCApp::InitMenu()
 		}	
 		
 		if (f.ReadLine(str)) it->AddNodeGo(new JTextMenuEntry(str, 0, 0)); else return false;                  //  Sound
+#endif
 		{
 			if (f.ReadLine(str)) it->AddBranchGo(new JTextMenuEntry(str, &OnSound, (void*)1)); else return false;//   On
 			if (f.ReadLine(str)) it->AddNodeGo(new JTextMenuEntry(str, &OnSound, (void*)0)); else return false;  //   Off