diff --git a/savemem.cpp b/savemem.cpp
new file mode 100644
index 00000000..71811bac
--- /dev/null
+++ b/savemem.cpp
@@ -0,0 +1,167 @@
+bool memory_saving_mode = true;
+
+#define LIM 150
+
+heptagon *last_cleared;
+
+void destroycellcontents(cell *c) {
+  c->land = laMemory;
+  c->wall = waChasm;
+  c->item = itNone;
+  if(!isMultitile(c->monst) && c->monst != moPair)
+    c->monst = moNone;
+  }
+
+void degrade(cell *c) {
+  c->mpdist++;
+  forCellEx(c2, c)
+    if(c2->mpdist < c->mpdist - 1)
+      degrade(c2);
+  destroycellcontents(c);
+  }
+
+vector<cell*> removed_cells;
+  
+
+void slow_delete_cell(cell *c) {
+  while(c->mpdist < BARLEV)
+    degrade(c);
+  for(int i=0; i<c->type; i++)
+    if(c->mov[i])
+      c->mov[i]->mov[c->spn(i)] = NULL;
+  removed_cells.push_back(c);
+  delete c;
+  }
+
+void delete_heptagon(heptagon *h2) {
+  cell *c = h2->c7;
+  if(!nonbitrunc) {
+    for(int i=0; i<c->type; i++)
+      if(c->mov[i])
+        slow_delete_cell(c->mov[i]);
+    }
+  slow_delete_cell(c);
+  for(int i=0; i<S7; i++)
+    if(h2->move[i])
+      h2->move[i]->move[h2->spin(i)] = NULL;
+  delete h2;
+  }
+
+void recursive_delete(heptagon *h, int i) {
+  heptagon *h2 = h->move[i];
+  for(int i=1; i<S7; i++)
+    if(h2->move[i] && h2->move[i]->move[0] == h2)
+      recursive_delete(h2, i);
+  if(h2->alt && h2->alt->alt == h2->alt) {
+    DEBSM(printf("destroying alternate map %p\n", h2->alt);)
+    for(hrmap *& hm: allmaps) {
+      auto hm2 = dynamic_cast<hrmap_alternate*> (hm);
+      if(hm2 && hm2->origin == h2->alt) {
+        delete hm;
+        hm = allmaps.back();
+        allmaps.pop_back();
+        DEBSM(printf("map found (%d altmaps total)\n", size(allmaps));)
+        break;
+        }
+      }
+    }
+  if(h2->alt) {
+    h2->alt->cdata = NULL;
+    }
+  delete_heptagon(h2);
+  h->move[i] = NULL;  
+  }
+
+bool unsafeLand(cell *c) {
+  return
+    isCyclic(c->land) || isGravityLand(c->land) || isHaunted(c->land) ||
+    among(c->land, laCaribbean, laOcean, laGraveyard, laPrincessQuest);
+  }
+
+void save_memory() {
+  if(quotient || !hyperbolic) return;
+  if(!memory_saving_mode) return;
+  if(unsafeLand(cwt.c)) return;
+  int d = celldist(cwt.c);
+  if(d < LIM+10) return;
+
+  heptagon *at = cwt.c->master;
+  heptagon *orig = currentmap->gamestart()->master;
+  
+  if(recallCell) {
+    if(unsafeLand(recallCell)) return;
+    heptagon *at2 = recallCell->master;
+    int t = 0;
+    while(at != at2) {
+      t++; if(t > 10000) return;
+      if(celldist(at->c7) > celldist(at2->c7))
+        at = at->move[0];
+      else
+        at2 = at2->move[0];
+      }
+    }
+  
+  while(celldist(at->c7) > d-LIM) at = at->move[0];
+  
+  // go back to such a point X that all the heptagons adjacent to the current 'at'
+  // are the children of X. This X becomes the new 'at'
+  if(true) {
+    heptagon *allh[9];
+    int hcount = 0;
+    allh[hcount++] = at;
+    for(int j=0; j<S7; j++) 
+      if(allh[0]->move[j])
+        allh[hcount++] = at->move[j];
+      
+    int deuniq_steps = 0;
+    
+    int i = 1;
+    while(i < hcount) {
+      if(allh[i] == allh[0])
+        allh[i] = allh[hcount-1], hcount--;
+      else if(celldist(allh[i]->c7) > celldist(allh[0]->c7))
+        allh[i] = allh[i]->move[0];
+      else {
+        if(allh[0] == orig) return;
+        allh[0] = allh[0]->move[0];
+        i = 1;
+        deuniq_steps++;
+        if(deuniq_steps == 10) return;
+        }
+      }
+    
+    at = allh[0];
+    }
+  
+  if(last_cleared && celldist(at->c7) < celldist(last_cleared->c7))
+    return;
+
+  DEBSM(printf("celldist = %d, %d\n", celldist(cwt.c), celldist(at->c7));)
+  
+  heptagon *at1 = at;
+  while(at != last_cleared && at != orig) {
+    heptagon *atn = at;
+    at = at->move[0];
+    
+    for(int i=1; i<S7; i++)
+      if(at->move[i] && at->move[i] != atn)
+        recursive_delete(at, i);
+    }
+  
+  last_cleared = at1;
+  DEBSM(printf("current cellcount = %d\n", cellcount);)
+  
+  sort(removed_cells.begin(), removed_cells.end());
+  callhooks(hooks_removecells);
+  removed_cells.clear();
+  }
+
+purehookset hooks_removecells;
+
+bool is_cell_removed(cell *c) {
+  return binary_search(removed_cells.begin(), removed_cells.end(), c);
+  }
+
+void set_if_removed(cell*& c, cell *val) {
+  if(is_cell_removed(c)) c = val;
+  }