diff --git a/bigstuff.cpp b/bigstuff.cpp
index 97ec7d4c..dbec0eb3 100644
--- a/bigstuff.cpp
+++ b/bigstuff.cpp
@@ -977,7 +977,7 @@ int wallchance(cell *c, bool deepOcean) {
 bool horo_ok() {
   // do the horocycles work in the current geometry?
   // (they work in ALL hyperbolic geometries currently!)
-  return hyperbolic && !irr::on;
+  return hyperbolic;
   }
 
 bool gp_wall_test() {
@@ -1085,7 +1085,7 @@ void buildBigStuff(cell *c, cell *from) {
     }
       
   if((!chaosmode) && bearsCamelot(c->land) && is_master(c) && 
-    (quickfind(laCamelot) || peace::on || (hrand(I2000) < 200 && ((irr::on && hyperbolic) || horo_ok()) && 
+    (quickfind(laCamelot) || peace::on || (hrand(I2000) < 200 && horo_ok() && 
     items[itEmerald] >= U5 && !tactic::on))) {
     int rtr = newRoundTableRadius();
     heptagon *alt = createAlternateMap(c, rtr+14, hsOrigin);
diff --git a/complex.cpp b/complex.cpp
index 57c088ff..c681d97a 100644
--- a/complex.cpp
+++ b/complex.cpp
@@ -821,7 +821,7 @@ namespace clearing {
   void generate(cell *c) {
     if(buggyplant) return;    
     if(sphere) return;    
-    if(gp::on) return;
+    if(gp::on || irr::on) return;
     if(quotient) return;
     
     if(euclid) {
diff --git a/hyper.h b/hyper.h
index 71b275e1..028c045b 100644
--- a/hyper.h
+++ b/hyper.h
@@ -522,7 +522,6 @@ bool destroyHalfvine(cell *c, eWall newwall = waNone, int tval = 6);
 void buildCrossroads2(cell *c);
 bool isHaunted(eLand l);
 heptagon *createAlternateMap(cell *c, int rad, hstate firststate, int special=0);
-void generateAlts(heptagon *h, int levs = S3-3, bool link_cdata = true);
 void setdist(cell *c, int d, cell *from);
 void checkOnYendorPath();
 void killThePlayerAt(eMonster m, cell *c, flagtype flags);
@@ -3714,4 +3713,6 @@ extern ld hexshift;
 
 extern bool noshadow, bright, nohelp, dont_face_pc;
 extern void switchHardcore();
+
+void generateAlts(heptagon *h, int levs = irr::on ? 1 : S3-3, bool link_cdata = true);
 }
diff --git a/irregular.cpp b/irregular.cpp
index 2d220ec2..75b509ba 100644
--- a/irregular.cpp
+++ b/irregular.cpp
@@ -506,7 +506,25 @@ int hdist(heptagon *h1, heptagon *h2) {
 // - compute celldists for all the cells in these three heptagons, by bfs, based on the 'parent' heptagons adjacent to h
 // - record the computed distances for h, but not for its siblings
 
+static const int NODISTANCE = 2000000000;
+
+map<heptagon*, heptagon*> last_on_horocycle;
+
+void compute_horocycle(heptagon *);
+
 void compute_distances(heptagon *h, bool alts) {
+  /* if(alts) printf("[%p] compute_distances %p\n", h->alt->alt, h);
+  printf("neighbors:"); for(int i=0; i<S7; i++) printf(" %p", createStep(h, i)); printf("\n"); */
+  
+  if(alts) {
+    if(!last_on_horocycle[h->alt->alt])
+      last_on_horocycle[h->alt->alt] = h;
+    
+    if(h->alt->alt->s != hsOrigin)
+    while(h->alt->distance <= last_on_horocycle[h->alt->alt]->alt->distance)
+      compute_horocycle(h->alt->alt);
+    }
+
   auto dm4 = [alts, h] (heptagon *h1) -> unsigned {
     if(!alts) return h1->dm4;
     if(alts && !h1->alt) return 100; // error
@@ -526,7 +544,7 @@ void compute_distances(heptagon *h, bool alts) {
     int ct = isize(hi.subcells);
     auto& cd = hi.celldists[alts];
     if(cd.empty() && hx != h) to_clear.push_back(&cd);
-    cd.resize(ct, 2000000000);
+    cd.resize(ct, NODISTANCE);
     if(h == hx && (alts ? h->alt->s == hsOrigin : h->s == hsOrigin))
       cd[0] = 0;
     }
@@ -544,14 +562,109 @@ void compute_distances(heptagon *h, bool alts) {
       }
     if(!changed) break;
     }
+
+  /* for(auto hx: hs) {
+    auto& hi = periodmap[hx];
+    auto& cd = hi.celldists[alts];
+    // for(int i: cd) if(i == NODISTANCE) printf("distances not computed\n");
+    } */
+
   for(auto x: to_clear) x->clear();
+
   // for(int i: cd) printf(" %d", i); printf("\n");
   }
 
+void erase_alt(heptagon *alt) { 
+  last_on_horocycle.erase(alt);
+  }
+
+void compute_horocycle(heptagon *alt) {
+  heptagon *master = last_on_horocycle[alt];
+  // printf("computing horocycle, master distance = %d [M=%p, A=%p]\n", master->alt->distance, master, alt);
+  
+  static const int LOOKUP = 16;
+  set<heptagon*> hs[LOOKUP];
+  hs[0].insert(master);
+  set<heptagon*> region;
+  for(int i=0; i<LOOKUP-1; i++) {
+    for(auto h: hs[i]) {
+      generateAlts(h);
+      for(int j=0; j<S7; j++) {
+        if(h->move[j]->alt->alt != master->alt->alt) continue;
+        region.insert(h->move[j]);
+        if(h->move[j]->alt->distance < h->alt->distance)
+          hs[i+1].insert(h->move[j]);
+        }
+      }
+    if(hs[i+1].empty()) { printf("error: hs[%d] not found\n", i+1); exit(1); }
+    }
+  /* printf("[%p] compute_horocycle ");
+  for(int i=0; i<LOOKUP-1; i++) printf("%d -> ", isize(hs[i])); printf("%p\n", isize(hs[LOOKUP-1])); */
+  map<cell*, int> xdist; 
+  vector<cell*> xdqueue;
+  cell *orig = periodmap[*(hs[LOOKUP-1].begin())].subcells[0];
+  xdist[orig] = 0;
+  xdqueue.push_back(orig);
+  for(int i=0; i<isize(xdqueue); i++) {
+    forCellCM(c1, xdqueue[i])
+      if(!xdist.count(c1) && region.count(c1->master)) {
+        xdist[c1] = xdist[xdqueue[i]] + 1;
+        xdqueue.push_back(c1);
+        }
+    }
+  int delta = NODISTANCE;
+  for(int i=0; i<S7; i++) {
+    heptagon *h = master->move[i];
+    if(h->alt->alt != master->alt->alt) continue;
+    heptinfo& hi = periodmap[h];
+    if(!isize(hi.celldists[1])) continue;
+    for(int c=0; c<isize(hi.subcells); c++) {
+      if(hi.celldists[1][c] == NODISTANCE) continue;
+      int delta_candidate = hi.celldists[1][c] - xdist[hi.subcells[c]];
+      if(delta != NODISTANCE && delta_candidate != delta) {
+        printf("delta conflict: %d vs %d\n", delta, delta_candidate);
+        delta = max(delta, delta_candidate);
+        }
+      delta = delta_candidate;
+      }
+    }
+  if(delta == NODISTANCE) {
+    delta = master->alt->distance - xdist[periodmap[master].subcells[0]];
+    // printf("delta not found, set to %d\n", delta);
+    }
+  // printf("using delta = %d\n", delta);
+
+  for(int i=0; i<LOOKUP/2; i++) {
+    for(auto h: hs[i]) for(int j=-1; j<S7; j++) {
+      heptinfo& hi = periodmap[j == -1 ? h : h->move[j]];
+      hi.celldists[1].resize(isize(hi.subcells));
+      for(int c=0; c<isize(hi.subcells); c++)
+        hi.celldists[1][c] = delta + xdist[hi.subcells[c]];
+      }
+    }
+
+  last_on_horocycle[alt] = *(hs[LOOKUP/2].begin());
+  }
+
 int celldist(cell *c, bool alts) {
   heptagon *master = c->master;
   auto &hi = periodmap[master];
-  if(isize(hi.celldists[alts]) == 0)
+  /* if(alts && master->alt->alt->s != hsOrigin && isize(hi.celldists[alts]) == 0) {
+    int doalts = 0;
+    for(int i=0; i<S7; i++) if(master->move[i]->alt == master->alt->move[0]) {
+      doalts = 1;
+      if(periodmap[master->move[i]].celldists[true].empty()) {
+        compute_horocycle(master);
+        doalts = 2;
+        }
+      }
+    if(doalts == 0) {
+      generateAlts(master);
+      for(int i=0; i<S7; i++) if(master->move[i]->alt == master->alt->move[0] && periodmap[master->move[i]].celldists[true].empty())
+        compute_horocycle(master);
+      }
+    } */
+  if(isize(hi.celldists[alts]) == 0) 
     compute_distances(master, alts);
   return hi.celldists[alts][cells[cellindex[c]].localindex];
   }
diff --git a/landlock.cpp b/landlock.cpp
index 8d01aff4..105c4afb 100644
--- a/landlock.cpp
+++ b/landlock.cpp
@@ -1162,12 +1162,9 @@ land_validity_t& land_validity(eLand l) {
   if((isWarped(l) || l == laDual) && irr::on)
     return dont_work;
   
-  if(irr::on && among(l, laStorms, laPrairie, laBlizzard, laVolcano))
+  if(irr::on && among(l, laPrairie, laBlizzard, laVolcano, laMirror, laMirrorOld))
     return dont_work;
 
-  if(irr::on && among(l, laWhirlpool, laCamelot, laCaribbean, laClearing, laTemple, laHive, laMirror, laMirrorOld, laReptile))
-    return dont_work;
-  
   // equidistant-based lands
   if(isEquidLand(l)) {
     // no equidistants supported in chaos mode
@@ -1201,7 +1198,7 @@ land_validity_t& land_validity(eLand l) {
     return not_in_chaos;
   
   if(l == laClearing)
-    if(!(stdeuc || a38 || (a45 && !nonbitrunc) || (a47 && !nonbitrunc)) || gp::on)
+    if(!(stdeuc || a38 || (a45 && !nonbitrunc) || (a47 && !nonbitrunc)) || gp::on || irr::on)
     if(!bounded)
       return not_implemented;
 
@@ -1313,7 +1310,7 @@ land_validity_t& land_validity(eLand l) {
   if(l == laTrollheim && !stdeuc && !bounded)
     return some1;
   
-  if(l == laReptile && (a38 || a4 || sphere || nonbitrunc || gp::on || (quotient && geometry != gZebraQuotient)))
+  if(l == laReptile && (a38 || a4 || sphere || nonbitrunc || gp::on || irr::on || (quotient && geometry != gZebraQuotient)))
     return bad_graphics;
 
   if((l == laDragon || l == laReptile) && !stdeuc && !smallbounded && !randomPatternsMode)