diff --git a/includes/defines.h b/includes/defines.h
index 69136c3d8..041c4239d 100644
--- a/includes/defines.h
+++ b/includes/defines.h
@@ -119,6 +119,7 @@ int GRAV_G2;
 int GRAV_B2;
 
 extern int legacy_enable;
+extern int ngrav_enable; //Newtonian gravity
 extern int sound_enable;
 extern int kiosk_enable;
 
diff --git a/includes/interface.h b/includes/interface.h
index 7cbdeea3e..9dc07f886 100644
--- a/includes/interface.h
+++ b/includes/interface.h
@@ -241,6 +241,8 @@ int report_ui(pixel *vid_buf, char *save_id);
 
 char *console_ui(pixel *vid_buf, char error[255],char console_more);
 
-void decorations_ui(pixel *vid_buf,pixel *decorations,int *bsx,int *bsy);
+void simulation_ui(pixel *vid_buf);
+
+void decorations_ui(pixel *vid_buf, pixel *decorations, int *bsx, int *bsy);
 #endif
 
diff --git a/src/interface.c b/src/interface.c
index b31a107a4..2cc3031ae 100644
--- a/src/interface.c
+++ b/src/interface.c
@@ -591,16 +591,16 @@ void draw_svf_ui(pixel *vid_buf)// all the buttons at the bottom
 		drawrect(vid_buf, XRES-16+BARSIZE/*494*/, YRES+(MENUSIZE-16), 14, 14, 255, 255, 255, 255);
 	}
 
-	//the heat sim button
-	if (!legacy_enable)
+	//The simulation options button, used to be the heat sim button
+	/*if (!legacy_enable)
 	{
-		fillrect(vid_buf, XRES-160+BARSIZE/*493*/, YRES+(MENUSIZE-17), 16, 16, 255, 255, 255, 255);
-		drawtext(vid_buf, XRES-154+BARSIZE/*481*/, YRES+(MENUSIZE-13), "\xBE", 255, 0, 0, 255);
-		drawtext(vid_buf, XRES-154+BARSIZE/*481*/, YRES+(MENUSIZE-13), "\xBD", 0, 0, 0, 255);
+		fillrect(vid_buf, XRES-160+BARSIZE, YRES+(MENUSIZE-17), 16, 16, 255, 255, 255, 255);
+		drawtext(vid_buf, XRES-154+BARSIZE, YRES+(MENUSIZE-13), "\xBE", 255, 0, 0, 255);
+		drawtext(vid_buf, XRES-154+BARSIZE, YRES+(MENUSIZE-13), "\xBD", 0, 0, 0, 255);
 	}
-	else
+	else*/
 	{
-		drawtext(vid_buf, XRES-154+BARSIZE/*481*/, YRES+(MENUSIZE-13), "\xBD", 255, 255, 255, 255);
+		drawtext(vid_buf, XRES-154+BARSIZE/*481*/, YRES+(MENUSIZE-13), "\xBD", 255, 255, 255, 255); //TODO: More suitable icon
 		drawrect(vid_buf, XRES-159+BARSIZE/*494*/, YRES+(MENUSIZE-16), 14, 14, 255, 255, 255, 255);
 	}
 
@@ -4501,3 +4501,79 @@ void decorations_ui(pixel *vid_buf,pixel *decorations,int *bsx,int *bsy)
 	}
 	free(old_buf);
 }
+
+void simulation_ui(pixel * vid_buf)
+{
+	int xsize = 300;
+	int ysize = 100;
+	int x0=(XRES-xsize)/2,y0=(YRES-MENUSIZE-ysize)/2,b=1,bq,mx,my;
+	ui_checkbox cb;
+	ui_checkbox cb2;
+
+	cb.x = x0+xsize-16;
+	cb.y = y0+23;
+	cb.focus = 0;
+	cb.checked = !legacy_enable;
+
+	cb2.x = x0+xsize-16;
+	cb2.y = y0+51;
+	cb2.focus = 0;
+	cb2.checked = ngrav_enable;
+
+	while (!sdl_poll())
+	{
+		b = SDL_GetMouseState(&mx, &my);
+		if (!b)
+			break;
+	}
+
+	while (!sdl_poll())
+	{
+		bq = b;
+		b = SDL_GetMouseState(&mx, &my);
+		mx /= sdl_scale;
+		my /= sdl_scale;
+
+		clearrect(vid_buf, x0-2, y0-2, xsize+4, ysize+4);
+		drawrect(vid_buf, x0, y0, xsize, ysize, 192, 192, 192, 255);
+		drawtext(vid_buf, x0+8, y0+8, "Simulation options", 255, 216, 32, 255);
+
+		drawtext(vid_buf, x0+8, y0+26, "Heat simulation", 255, 255, 255, 255);
+		drawtext(vid_buf, x0+12+textwidth("Heat simulation"), y0+26, "Introduced in version 34.", 255, 255, 255, 180);
+		drawtext(vid_buf, x0+12, y0+40, "Older saves may behave oddly with this enabled.", 255, 255, 255, 180);
+
+		drawtext(vid_buf, x0+8, y0+54, "Newtonian gravity", 255, 255, 255, 255);
+		drawtext(vid_buf, x0+12+textwidth("Newtonian gravity"), y0+54, "Introduced in version 48.", 255, 255, 255, 180);
+		drawtext(vid_buf, x0+12, y0+68, "May also cause slow performance on older computers", 255, 255, 255, 180);
+
+		//TODO: Options for Air and Normal gravity
+		//Maybe save/load defaults too.
+
+		drawtext(vid_buf, x0+5, y0+ysize-11, "OK", 255, 255, 255, 255);
+		drawrect(vid_buf, x0, y0+ysize-16, xsize, 16, 192, 192, 192, 255);
+
+		ui_checkbox_draw(vid_buf, &cb);
+		ui_checkbox_draw(vid_buf, &cb2);
+		sdl_blit(0, 0, (XRES+BARSIZE), YRES+MENUSIZE, vid_buf, (XRES+BARSIZE));
+		ui_checkbox_process(mx, my, b, bq, &cb);
+		ui_checkbox_process(mx, my, b, bq, &cb2);
+
+		if (b && !bq && mx>=x0 && mx<x0+xsize && my>=y0+ysize-16 && my<=y0+ysize)
+			break;
+
+		if (sdl_key==SDLK_RETURN)
+			break;
+		if (sdl_key==SDLK_ESCAPE)
+			break;
+	}
+
+	legacy_enable = !cb.checked;
+	ngrav_enable = cb2.checked;
+
+	while (!sdl_poll())
+	{
+		b = SDL_GetMouseState(&mx, &my);
+		if (!b)
+			break;
+	}
+}
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
index 8d4b8870d..ae62efcff 100644
--- a/src/main.c
+++ b/src/main.c
@@ -170,7 +170,8 @@ float mheat = 0.0f;
 int do_open = 0;
 int sys_pause = 0;
 int sys_shortcuts = 1;
-int legacy_enable = 0; //Used to disable new features such as heat, will be set by commandline or save.
+int legacy_enable = 0; //Used to disable new features such as heat, will be set by save.
+int ngrav_enable = 1; //Newtonian gravity, will be set by save TODO: Make this actually do something
 int death = 0, framerender = 0;
 int amd = 1;
 int FPSB = 0;
@@ -2545,7 +2546,8 @@ int main(int argc, char *argv[])
 						tag_list_ui(vid_buf);
 					if (x>=(XRES+BARSIZE-(510-351)) && x<(XRES+BARSIZE-(510-366)) && !bq)
 					{
-						legacy_enable = !legacy_enable;
+						//legacy_enable = !legacy_enable;
+						simulation_ui(vid_buf);
 					}
 					if (x>=(XRES+BARSIZE-(510-367)) && x<=(XRES+BARSIZE-(510-383)) && !bq)
 					{