diff --git a/complex.cpp b/complex.cpp
index 8610a898..f4711b4c 100644
--- a/complex.cpp
+++ b/complex.cpp
@@ -917,7 +917,7 @@ EX namespace clearing {
       // printf("R %4d C %4d\n", celldistAlt(bd.root), celldistAlt(c));
       if(celldistAlt(c) > celldistAlt(bd.root)) {
         stepcount++;
-        if(stepcount > 100000000) {
+        if(stepcount > iteration_limit) {
           printf("buggy #1\n");
           bd.buggy = true;
           return;
@@ -937,7 +937,7 @@ EX namespace clearing {
         }
       else {
         bd.dist--;
-        if(bd.dist < -100000000) { 
+        if(bd.dist < -iteration_limit) { 
           for(int i=0; i<steps; i++) 
             onpath[i]->item = itBuggy;
           for(int i=0; i<(int) rpath.size(); i++) 
@@ -2562,7 +2562,7 @@ EX namespace dragon {
   EX cell *target; // actually for all Orb of Control
 
   void pullback(cell *c) {
-    int maxlen = 1000;
+    int maxlen = iteration_limit;
     while(maxlen-->0) {
       auto mi = moveimon(c).rev();
       mountmove(mi, true);
@@ -2579,7 +2579,7 @@ EX namespace dragon {
   
   EX cell *findhead(cell *c) {
     cell *cor = c;
-    int maxlen=1000;
+    int maxlen=iteration_limit;
     findhead:  
     if(maxlen--<0) return c;
     if(c->monst == moDragonHead) return c;
@@ -2608,7 +2608,7 @@ EX namespace dragon {
   
   EX int bodypart(cell *c, cell *head) {
     int i = 0, j = 0;
-    int maxlen = 1000;
+    int maxlen = iteration_limit;
     while(maxlen-->0) {
       if(head == c) i = j;
       j++;
@@ -2627,7 +2627,7 @@ EX namespace dragon {
     int delay = false;
     kills[moDragonHead]++;
     int penalty = 0;
-    int maxlen = 1000;
+    int maxlen = iteration_limit;
     while(maxlen-->0) {
       changes.ccell(c);
       makeflame(c, 5, false);
@@ -2657,7 +2657,7 @@ EX namespace dragon {
   
   EX int totalhp(cell *c) {
     int total = 0;
-    int maxlen = 1000;
+    int maxlen = iteration_limit;
     while(maxlen-->0) {
       if(!isDragon(c->monst)) {
         if(!history::includeHistory) printf("dragon bug #4\n");
@@ -2673,7 +2673,7 @@ EX namespace dragon {
   #define SWAPBITFIELD(x,y,t) { t bak=x; x=y; y=bak; }
   
   void pullfront(cell *c, cell *until) {
-    int maxlen = 1000;
+    int maxlen = iteration_limit;
     static vector<cell*> allcells;
     allcells.clear();
     while(maxlen-->0) {
diff --git a/game.cpp b/game.cpp
index ca98017d..2d1c5c9e 100644
--- a/game.cpp
+++ b/game.cpp
@@ -401,37 +401,36 @@ EX void fixWormBug(cell *c) {
   if(c->monst == moTentacletail || c->monst == moTentacleGhost) c->monst = moTentacle;
   if(c->monst == moHexSnakeTail) c->monst = moHexSnake;
   }
-  
+
+EX bool isWormhead(eMonster m) {
+  return among(m, 
+    moTentacle, moWorm, moHexSnake, moWormwait, moTentacleEscaping,
+    moTentaclewait, moDragonHead);   
+  }
+
+EX cell *worm_tohead(cell *c) {
+ for(int i=0; i<c->type; i++)
+   if(c->move(i) && isWorm(c->move(i)->monst) && c->move(i)->mondir == c->c.spin(i))
+     return c->move(i);
+  return nullptr;
+  }
+
 EX cell *wormhead(cell *c) {
   // cell *cor = c;
-  findhead:  
-  if(c->monst == moTentacle || c->monst == moWorm || c->monst == moHexSnake ||
-    c->monst == moWormwait || c->monst == moTentacleEscaping || c->monst == moTentaclewait ||
-    c->monst == moDragonHead) return c;
-  for(int i=0; i<c->type; i++)
-    if(c->move(i) && isWorm(c->move(i)->monst) && c->move(i)->mondir == c->c.spin(i)) {
-      c = c->move(i); goto findhead;
-      }
+  int cnt = 0;
+  while(cnt < iteration_limit) {
+    if(isWormhead(c->monst))
+      return c;
+    cell *c1 = worm_tohead(c);
+    if(!c1) break;
+    c = c1;
+    cnt++;
+    }
   fixWormBug(c);
   return c;
-  }
+  }  
   
-EX int wormpos(cell *c) {
-  // cell *cor = c;
-  int cnt = 0;
-  findhead:  
-  if(c->monst == moTentacle || c->monst == moWorm || c->monst == moHexSnake ||
-    c->monst == moWormwait || c->monst == moTentacleEscaping || c->monst == moTentaclewait ||
-    c->monst == moDragonHead) return cnt;
-  for(int i=0; i<c->type; i++)
-    if(c->move(i) && isWorm(c->move(i)->monst) && c->move(i)->mondir == c->c.spin(i)) {
-      c = c->move(i); cnt++; goto findhead;
-      }
-  fixWormBug(c);
-  return cnt;
-  }
-  
-// currently works for worms only
+/** currently works for worms only */
 EX bool sameMonster(cell *c1, cell *c2) {
   if(!c1 || !c2) return false;
   if(c1 == c2) return true;
diff --git a/heptagon.cpp b/heptagon.cpp
index d0379225..bff3e629 100644
--- a/heptagon.cpp
+++ b/heptagon.cpp
@@ -237,7 +237,7 @@ heptagon *hrmap_standard::create_step(heptagon *h, int d) {
       pard = 3; // to do: randomize
     else if(S3 == 4)
       pard = 3;
-    buildHeptagon(h, 0, h->distance < -32500 ? hsOrigin : hsA, pard);
+    buildHeptagon(h, 0, h->distance < -global_distance_limit - 200 ? hsOrigin : hsA, pard);
     }
   if(h->move(d)) return h->move(d);
   if(h->s == hsOrigin) {
diff --git a/landgen.cpp b/landgen.cpp
index 6c1899d6..0bd45970 100644
--- a/landgen.cpp
+++ b/landgen.cpp
@@ -2899,7 +2899,8 @@ EX void setdist(cell *c, int d, cell *from) {
   if(d == 7) repairLandgen(c);
   
   // the number of tiles in the standard geometry has about 7553 digits!
-  if(c->master->distance > 32000 || c->master->distance < -32000) {
+  int gdist = abs(c->master->distance);
+  if(gdist > global_distance_limit) {
     c->wall = waNone;
     c->item = itOrbSafety;
     }
diff --git a/locations.cpp b/locations.cpp
index e83c7777..7630f6bd 100644
--- a/locations.cpp
+++ b/locations.cpp
@@ -288,6 +288,18 @@ struct cdata {
   int bits;
   };
 
+/** Limit on the 'distance' value in heptagon. This value is signed (negative distances are used
+    in horocycle implementation. Distance is currently a short, and we need a bit of breathing room.
+    It would not be a technical problem to use a larger type, but 32000 is close to what fits in
+    the memory of a normal computer. Farlands appear close to this limit.
+    */
+    
+constexpr int global_distance_limit = 32000;
+
+/** This value is used in iterative algorithms to prevent infinite loops created by incorrect
+    data (e.g., circular dragon). It should be larger than global_distance_limit */
+constexpr int iteration_limit = 10000000;
+
 /** in bitruncated/irregular/Goldberg geometries, heptagons form the 
  *  underlying regular tiling (not necessarily heptagonal); in pure
  *  geometries, they correspond 1-1 to tiles; in 'masterless' geometries