Tourists gain experience by seeing new types of creatures up close

Experience equivalent to killing a monster is gained when starting a turn
adjacent to and being able to see the monster.

Breaks saves.

Idea and parts of code via dNetHack

src/allmain.c

@@ -14,6 +14,7 @@
 
 staticfn void moveloop_preamble(boolean);
 staticfn void u_calc_moveamt(int);
+staticfn void see_nearby_monsters(void);
 staticfn void maybe_do_tutorial(void);
 #ifdef POSITIONBAR
 staticfn void do_positionbar(void);
@@ -154,6 +155,28 @@ u_calc_moveamt(int wtcap)
         u.umovement = 0;
 }
 
+/* mark a monster type as seen when we see it next to us */
+staticfn void
+see_nearby_monsters(void)
+{
+    coordxy x, y;
+
+    if (Blind || !Role_if(PM_TOURIST))
+        return;
+
+    for (x = u.ux - 1; x <= u.ux + 1; x++)
+        for (y = u.uy - 1; y <= u.uy + 1; y++)
+            if (isok(x, y) && MON_AT(x, y)) {
+                struct monst *mtmp = m_at(x, y);
+
+                if (canseemon(mtmp) && !svm.mvitals[monsndx(mtmp->data)].seen_close) {
+                    svm.mvitals[monsndx(mtmp->data)].seen_close = TRUE;
+                    more_experienced(experience(mtmp, 0), 0);
+                    newexplevel();
+                }
+            }
+}
+
 #if defined(MICRO) || defined(WIN32)
 static int mvl_abort_lev;
 #endif
@@ -410,6 +433,7 @@ moveloop_core(void)
         else if (u.uburied)
             under_ground(0);
 
+        see_nearby_monsters();
     } /* actual time passed */
 
     /****************************************/