diff -u -r tworld-1.2.1/solution.c tworld-1.2.1-ruleswitch/solution.c
--- tworld-1.2.1/solution.c	2004-10-13 13:39:32.000000000 +0100
+++ tworld-1.2.1-ruleswitch/solution.c	2005-12-30 14:51:12.000000000 +0000
@@ -425,7 +425,7 @@
 
 /* Locate the solution file for the given data file and open it.
  */
-static int opensolutionfile(fileinfo *file, char const *datname, int readonly)
+static int opensolutionfile(fileinfo *file, char const *datname, int ruleset, int readonly)
 {
     char       *buf = NULL;
     char const *filename;
@@ -439,9 +439,12 @@
 				  && tolower(datname[n - 2]) == 'a'
 				  && tolower(datname[n - 1]) == 't')
 	    n -= 4;
-	xalloc(buf, n + 5);
+	xalloc(buf, n + 7);
 	memcpy(buf, datname, n);
-	memcpy(buf + n, ".tws", 5);
+	memcpy(buf + n, "-m.tws", 7);
+        /* Add ruleset specifier */
+        if(ruleset == Ruleset_Lynx)
+            buf[n + 1] = 'l';
 	filename = buf;
     }
     n = openfileindir(file, savedir, filename,
@@ -462,8 +465,8 @@
     int		i, j;
 
     if (!savedir || !*savedir
-		 || !opensolutionfile(&series->solutionfile,
-				      series->filebase, TRUE)) {
+		 || !opensolutionfile(&series->solutionfile, series->filebase,
+				      series->ruleset, TRUE)) {
 	series->solutionflags = series->ruleset;
 	return TRUE;
     }
@@ -530,8 +533,8 @@
     }
     if (series->solutionfile.fp)
 	fileclose(&series->solutionfile, NULL);
-    if (!opensolutionfile(&series->solutionfile,
-			  series->filebase, FALSE)) {
+    if (!opensolutionfile(&series->solutionfile, series->filebase,
+			  series->ruleset, FALSE)) {
 	*savedir = '\0';
 	return FALSE;
     }
diff -u -r tworld-1.2.1/tworld.c tworld-1.2.1-ruleswitch/tworld.c
--- tworld-1.2.1/tworld.c	2004-10-21 20:25:20.000000000 +0100
+++ tworld-1.2.1-ruleswitch/tworld.c	2005-12-30 14:51:12.000000000 +0000
@@ -303,6 +303,8 @@
       case CmdProceed:		*move = CmdProceed;		return FALSE;
       case CmdQuitLevel:	*move = CmdQuitLevel;		return FALSE;
       case CmdHelp:		*move = CmdHelp;		return FALSE;
+      case CmdEast:		*move = CmdEast;		return FALSE;
+      case CmdWest:		*move = CmdWest;		return FALSE;
       case CmdQuit:						exit(0);
 
     }
@@ -1027,6 +1029,16 @@
 		pushsubtitle("Help");
 		onlinefirsthelp();
 		popsubtitle();
+	    } else if (f == CmdEast) {
+		getseriesfromlist(&gs->series, series->list, n);
+		gs->series.ruleset = Ruleset_Lynx;
+		okay = TRUE;
+		break;
+	    } else if (f == CmdWest) {
+		getseriesfromlist(&gs->series, series->list, n);
+		gs->series.ruleset = Ruleset_MS;
+		okay = TRUE;
+		break;
 	    }
 	}
     }