diff --git a/dat/themerms.lua b/dat/themerms.lua
index 454059125..b7e0f1f0a 100644
--- a/dat/themerms.lua
+++ b/dat/themerms.lua
@@ -2,12 +2,26 @@
 --	Copyright (c) 2020 by Pasi Kallinen
 -- NetHack may be freely redistributed.  See license for details.
 --
--- themerooms is an array of tables and/or functions.
--- the tables define "frequency", "contents", "mindiff" and "maxdiff".
--- frequency is optional; if omitted, 1 is assumed.
--- mindiff and maxdiff are optional and independent; if omitted, the room is
--- not constrained by level difficulty.
--- a plain function has frequency of 1, and no difficulty constraints.
+-- themerooms is an array of tables.
+-- the tables define "name", "frequency", "contents", "mindiff" and "maxdiff".
+-- * "name" is not shown in-game; it is so that developers can specify a certain
+--   room to generate by using the THEMERM or THEMERMFILL environment variable.
+--   While technically optional, it should be provided on all the rooms; if it
+--   isn't, the room can't be directly specified.
+-- * "frequency" is optional; if omitted, 1 is assumed.
+-- * "contents" is a function describing what gets put into the room.
+-- * "mindiff" and "maxdiff" are optional and independent; if omitted, the room
+--    is not constrained by level difficulty.
+--
+-- themeroom_fills is an array of tables with the exact same structure as
+-- themerooms. It is used for contents of a room that are independent of its
+-- shape, so that interestingly-shaped themerooms can be filled with a variety
+-- of contents.
+-- * The "contents" functions in themeroom_fills take the room they are filling as
+--   an argument.
+-- * Frequency of themeroom_fills is a separate pool from themerooms, and has no
+--   effect on how likely it is that any given room will receive a themeroom_fill.
+--
 -- des.room({ type = "ordinary", filled = 1 })
 --   - ordinary rooms can be converted to shops or any other special rooms.
 --   - filled = 1 means the room gets random room contents, even if it
@@ -24,35 +38,38 @@
 -- The lua state is persistent through the gameplay, but not across saves,
 -- so remember to reset any variables.
 
-
 local postprocess = { };
 
 themeroom_fills = {
 
-   -- Ice room
-   function(rm)
-      local ice = selection.room();
-      des.terrain(ice, "I");
-      if (percent(25)) then
-         local mintime = 1000 - (nh.level_difficulty() * 100);
-         local ice_melter = function(x,y)
-            nh.start_timer_at(x,y, "melt-ice", mintime + nh.rn2(1000));
-         end;
-         ice:iterate(ice_melter);
-      end
-   end,
-
-   -- Cloud room
-   function(rm)
-      local fog = selection.room();
-      for i = 1, (fog:numpoints() / 4) do
-         des.monster({ id = "fog cloud", asleep = true });
-      end
-      des.gas_cloud({ selection = fog });
-   end,
-
-   -- Boulder room
    {
+      name = "Ice room",
+      contents = function(rm)
+         local ice = selection.room();
+         des.terrain(ice, "I");
+         if (percent(25)) then
+            local mintime = 1000 - (nh.level_difficulty() * 100);
+            local ice_melter = function(x,y)
+               nh.start_timer_at(x,y, "melt-ice", mintime + nh.rn2(1000));
+            end;
+            ice:iterate(ice_melter);
+         end
+      end,
+   },
+
+   {
+      name = "Cloud room",
+      contents = function(rm)
+         local fog = selection.room();
+         for i = 1, (fog:numpoints() / 4) do
+            des.monster({ id = "fog cloud", asleep = true });
+         end
+         des.gas_cloud({ selection = fog });
+      end,
+   },
+
+   {
+      name = "Boulder room",
       mindiff = 4,
       contents = function(rm)
          local locs = selection.room():percentage(30);
@@ -64,35 +81,39 @@ themeroom_fills = {
             end
          end;
          locs:iterate(func);
-      end
+      end,
    },
 
-   -- Spider nest
-   function(rm)
-      local spooders = nh.level_difficulty() > 8;
-      local locs = selection.room():percentage(30);
-      local func = function(x,y)
-         des.trap({ type = "web", x = x, y = y,
-                    spider_on_web = spooders and percent(80) });
-      end
-      locs:iterate(func);
-   end,
-
-   -- Trap room
-   function(rm)
-      local traps = { "arrow", "dart", "falling rock", "bear",
-                      "land mine", "sleep gas", "rust",
-                      "anti magic" };
-      shuffle(traps);
-      local locs = selection.room():percentage(30);
-      local func = function(x,y)
-         des.trap(traps[1], x, y);
-      end
-      locs:iterate(func);
-   end,
-
-   -- Garden
    {
+      name = "Spider nest",
+      contents = function(rm)
+         local spooders = nh.level_difficulty() > 8;
+         local locs = selection.room():percentage(30);
+         local func = function(x,y)
+            des.trap({ type = "web", x = x, y = y,
+                       spider_on_web = spooders and percent(80) });
+         end
+         locs:iterate(func);
+      end,
+   },
+
+   {
+      name = "Trap room",
+      contents = function(rm)
+         local traps = { "arrow", "dart", "falling rock", "bear",
+                        "land mine", "sleep gas", "rust",
+                        "anti magic" };
+         shuffle(traps);
+         local locs = selection.room():percentage(30);
+         local func = function(x,y)
+            des.trap(traps[1], x, y);
+         end
+         locs:iterate(func);
+      end,
+   },
+
+   {
+      name = "Garden",
       eligible = function(rm) return rm.lit == true; end,
       contents = function(rm)
          local s = selection.room();
@@ -107,216 +128,242 @@ themeroom_fills = {
       end
    },
 
-   -- Buried treasure
-   function(rm)
-      des.object({ id = "chest", buried = true, contents = function(otmp)
-                      local xobj = otmp:totable();
-                      -- keep track of the last buried treasure
-                      if (xobj.NO_OBJ == nil) then
-                         table.insert(postprocess, { handler = make_dig_engraving, data = { x = xobj.ox, y = xobj.oy }});
-                      end
-                      for i = 1, d(3,4) do
-                         des.object();
-                      end
-      end });
-   end,
-
-   -- Buried zombies
-   function(rm)
-      local diff = nh.level_difficulty()
-      -- start with [1..4] for low difficulty
-      local zombifiable = { "kobold", "gnome", "orc", "dwarf" };
-      if diff > 3 then          -- medium difficulty
-         zombifiable[5], zombifiable[6] = "elf", "human";
-         if diff > 6 then       -- high difficulty (relatively speaking)
-            zombifiable[7], zombifiable[8] = "ettin", "giant";
-         end
-      end
-      for i = 1, (rm.width * rm.height) / 2 do
-         shuffle(zombifiable);
-         local o = des.object({ id = "corpse", montype = zombifiable[1],
-                                buried = true });
-         o:stop_timer("rot-corpse");
-         o:start_timer("zombify-mon", math.random(990, 1010));
-      end
-   end,
-
-   -- Massacre
-   function(rm)
-      local mon = { "apprentice", "warrior", "ninja", "thug",
-                    "hunter", "acolyte", "abbot", "page",
-                    "attendant", "neanderthal", "chieftain",
-                    "student", "wizard", "valkyrie", "tourist",
-                    "samurai", "rogue", "ranger", "priestess",
-                    "priest", "monk", "knight", "healer",
-                    "cavewoman", "caveman", "barbarian",
-                    "archeologist" };
-      local idx = math.random(#mon);
-      for i = 1, d(5,5) do
-         if (percent(10)) then idx = math.random(#mon); end
-         des.object({ id = "corpse", montype = mon[idx] });
-      end
-   end,
-
-   -- Statuary
-   function(rm)
-      for i = 1, d(5,5) do
-         des.object({ id = "statue" });
-      end
-      for i = 1, d(3) do
-         des.trap("statue");
-      end
-   end,
-
-   -- Light source
    {
+      name = "Buried treasure",
+      contents = function(rm)
+         des.object({ id = "chest", buried = true, contents = function(otmp)
+            local xobj = otmp:totable();
+            -- keep track of the last buried treasure
+            if (xobj.NO_OBJ == nil) then
+               table.insert(postprocess, { handler = make_dig_engraving, data = { x = xobj.ox, y = xobj.oy }});
+            end
+            for i = 1, d(3,4) do
+               des.object();
+            end
+         end });
+      end,
+   },
+
+   {
+      name = "Buried zombies",
+      contents = function(rm)
+         local diff = nh.level_difficulty()
+         -- start with [1..4] for low difficulty
+         local zombifiable = { "kobold", "gnome", "orc", "dwarf" };
+         if diff > 3 then          -- medium difficulty
+            zombifiable[5], zombifiable[6] = "elf", "human";
+            if diff > 6 then       -- high difficulty (relatively speaking)
+               zombifiable[7], zombifiable[8] = "ettin", "giant";
+            end
+         end
+         for i = 1, (rm.width * rm.height) / 2 do
+            shuffle(zombifiable);
+            local o = des.object({ id = "corpse", montype = zombifiable[1],
+                                 buried = true });
+            o:stop_timer("rot-corpse");
+            o:start_timer("zombify-mon", math.random(990, 1010));
+         end
+      end,
+   },
+
+   {
+      name = "Massacre",
+      contents = function(rm)
+         local mon = { "apprentice", "warrior", "ninja", "thug",
+                     "hunter", "acolyte", "abbot", "page",
+                     "attendant", "neanderthal", "chieftain",
+                     "student", "wizard", "valkyrie", "tourist",
+                     "samurai", "rogue", "ranger", "priestess",
+                     "priest", "monk", "knight", "healer",
+                     "cavewoman", "caveman", "barbarian",
+                     "archeologist" };
+         local idx = math.random(#mon);
+         for i = 1, d(5,5) do
+            if (percent(10)) then idx = math.random(#mon); end
+            des.object({ id = "corpse", montype = mon[idx] });
+         end
+      end,
+   },
+
+   {
+      name = "Statuary",
+      contents = function(rm)
+         for i = 1, d(5,5) do
+            des.object({ id = "statue" });
+         end
+         for i = 1, d(3) do
+            des.trap("statue");
+         end
+      end,
+   },
+
+
+   {
+      name = "Light source",
       eligible = function(rm) return rm.lit == false; end,
       contents = function(rm)
          des.object({ id = "oil lamp", lit = true });
       end
    },
 
-   -- Temple of the gods
-   function(rm)
-      des.altar({ align = align[1] });
-      des.altar({ align = align[2] });
-      des.altar({ align = align[3] });
-   end,
+   {
+      name = "Temple of the gods",
+      contents = function(rm)
+         des.altar({ align = align[1] });
+         des.altar({ align = align[2] });
+         des.altar({ align = align[3] });
+      end,
+   },
 
-   -- Ghost of an Adventurer
-   function(rm)
-      local loc = selection.room():rndcoord(0);
-      des.monster({ id = "ghost", asleep = true, waiting = true, coord = loc });
-      if percent(65) then
-         des.object({ id = "dagger", coord = loc, buc = "not-blessed" });
-      end
-      if percent(55) then
-         des.object({ class = ")", coord = loc, buc = "not-blessed" });
-      end
-      if percent(45) then
-         des.object({ id = "bow", coord = loc, buc = "not-blessed" });
-         des.object({ id = "arrow", coord = loc, buc = "not-blessed" });
-      end
-      if percent(65) then
-         des.object({ class = "[", coord = loc, buc = "not-blessed" });
-      end
-      if percent(20) then
-         des.object({ class = "=", coord = loc, buc = "not-blessed" });
-      end
-      if percent(20) then
-         des.object({ class = "?", coord = loc, buc = "not-blessed" });
-      end
-   end,
-
-   -- Storeroom
-   function(rm)
-      local locs = selection.room():percentage(30);
-      local func = function(x,y)
-         if (percent(25)) then
-            des.object("chest");
-         else
-            des.monster({ class = "m", appear_as = "obj:chest" });
+   {
+      name = "Ghost of an Adventurer",
+      contents = function(rm)
+         local loc = selection.room():rndcoord(0);
+         des.monster({ id = "ghost", asleep = true, waiting = true, coord = loc });
+         if percent(65) then
+            des.object({ id = "dagger", coord = loc, buc = "not-blessed" });
          end
-      end;
-      locs:iterate(func);
-   end,
-
-   -- Teleportation hub
-   function(rm)
-      local locs = selection.room():filter_mapchar(".");
-      for i = 1, 2 + nh.rn2(3) do
-         local pos = locs:rndcoord(1);
-         if (pos.x > 0) then
-            pos.x = pos.x + rm.region.x1 - 1;
-            pos.y = pos.y + rm.region.y1;
-            table.insert(postprocess, { handler = make_a_trap, data = { type = "teleport", seen = true, coord = pos, teledest = 1 } });
+         if percent(55) then
+            des.object({ class = ")", coord = loc, buc = "not-blessed" });
          end
-      end
-   end,
+         if percent(45) then
+            des.object({ id = "bow", coord = loc, buc = "not-blessed" });
+            des.object({ id = "arrow", coord = loc, buc = "not-blessed" });
+         end
+         if percent(65) then
+            des.object({ class = "[", coord = loc, buc = "not-blessed" });
+         end
+         if percent(20) then
+            des.object({ class = "=", coord = loc, buc = "not-blessed" });
+         end
+         if percent(20) then
+            des.object({ class = "?", coord = loc, buc = "not-blessed" });
+         end
+      end,
+   },
+
+   {
+      name = "Storeroom",
+      contents = function(rm)
+         local locs = selection.room():percentage(30);
+         local func = function(x,y)
+            if (percent(25)) then
+               des.object("chest");
+            else
+               des.monster({ class = "m", appear_as = "obj:chest" });
+            end
+         end;
+         locs:iterate(func);
+      end,
+   },
+
+   {
+      name = "Teleportation hub",
+      contents = function(rm)
+         local locs = selection.room():filter_mapchar(".");
+         for i = 1, 2 + nh.rn2(3) do
+            local pos = locs:rndcoord(1);
+            if (pos.x > 0) then
+               pos.x = pos.x + rm.region.x1 - 1;
+               pos.y = pos.y + rm.region.y1;
+               table.insert(postprocess, { handler = make_a_trap, data = { type = "teleport", seen = true, coord = pos, teledest = 1 } });
+            end
+         end
+      end,
+   },
 };
 
 themerooms = {
    {
-     -- the "default" room
+      name = "default",
       frequency = 1000,
       contents = function()
          des.room({ type = "ordinary", filled = 1 });
          end
    },
 
-   -- Fake Delphi
-   function()
-      des.room({ type = "ordinary", w = 11,h = 9, filled = 1,
-                 contents = function()
-                    des.room({ type = "ordinary", x = 4,y = 3, w = 3,h = 3, filled = 1,
-                               contents = function()
-                                  des.door({ state="random", wall="all" });
-                               end
-                    });
-                 end
-      });
-   end,
-
-   -- Room in a room
-   function()
-      des.room({ type = "ordinary", filled = 1,
-                 contents = function()
-                    des.room({ type = "ordinary",
-                               contents = function()
-                                  des.door({ state="random", wall="all" });
-                               end
-                    });
-                 end
-      });
-   end,
-
-   -- Huge room, with another room inside (90%)
-   function()
-      des.room({ type = "ordinary", w = nh.rn2(10)+11,h = nh.rn2(5)+8, filled = 1,
-                 contents = function()
-                    if (percent(90)) then
-                    des.room({ type = "ordinary", filled = 1,
-                               contents = function()
-                                  des.door({ state="random", wall="all" });
-                                  if (percent(50)) then
-                                     des.door({ state="random", wall="all" });
-                                  end
-                               end
-                    });
-                    end
-                 end
-      });
-   end,
-
-   -- Nesting rooms
-   function()
-      des.room({ type = "ordinary", w = 9 + nh.rn2(4), h = 9 + nh.rn2(4), filled = 1,
-                 contents = function(rm)
-                    local wid = math.random(math.floor(rm.width / 2), rm.width - 2);
-                    local hei = math.random(math.floor(rm.height / 2), rm.height - 2);
-                    des.room({ type = "ordinary", w = wid,h = hei, filled = 1,
-                               contents = function()
-                                  if (percent(90)) then
-                                     des.room({ type = "ordinary", filled = 1,
-                                                contents = function()
-                                                   des.door({ state="random", wall="all" });
-                                                   if (percent(15)) then
-                                                      des.door({ state="random", wall="all" });
-                                                   end
-                                                end
-                                     });
-                                  end
-                                  des.door({ state="random", wall="all" });
-                                  if (percent(15)) then
-                                     des.door({ state="random", wall="all" });
-                                  end
-                               end
-                    });
-                 end
-      });
-   end,
+   {
+      name = "Fake Delphi",
+      contents = function()
+         des.room({ type = "ordinary", w = 11,h = 9, filled = 1,
+                  contents = function()
+                     des.room({ type = "ordinary", x = 4,y = 3, w = 3,h = 3, filled = 1,
+                                 contents = function()
+                                    des.door({ state="random", wall="all" });
+                                 end
+                     });
+                  end
+         });
+      end,
+   },
 
    {
+      name = "Room in a room",
+      contents = function()
+         des.room({ type = "ordinary", filled = 1,
+                  contents = function()
+                     des.room({ type = "ordinary",
+                                 contents = function()
+                                    des.door({ state="random", wall="all" });
+                                 end
+                     });
+                  end
+         });
+      end,
+   },
+
+   {
+      name = "Huge room with another room inside",
+      contents = function()
+         des.room({ type = "ordinary", w = nh.rn2(10)+11,h = nh.rn2(5)+8, filled = 1,
+                  contents = function()
+                     if (percent(90)) then
+                     des.room({ type = "ordinary", filled = 1,
+                                 contents = function()
+                                    des.door({ state="random", wall="all" });
+                                    if (percent(50)) then
+                                       des.door({ state="random", wall="all" });
+                                    end
+                                 end
+                     });
+                     end
+                  end
+         });
+      end,
+   },
+
+   {
+      name = "Nesting rooms",
+      contents = function()
+         des.room({ type = "ordinary", w = 9 + nh.rn2(4), h = 9 + nh.rn2(4), filled = 1,
+                  contents = function(rm)
+                     local wid = math.random(math.floor(rm.width / 2), rm.width - 2);
+                     local hei = math.random(math.floor(rm.height / 2), rm.height - 2);
+                     des.room({ type = "ordinary", w = wid,h = hei, filled = 1,
+                                 contents = function()
+                                    if (percent(90)) then
+                                       des.room({ type = "ordinary", filled = 1,
+                                                   contents = function()
+                                                      des.door({ state="random", wall="all" });
+                                                      if (percent(15)) then
+                                                         des.door({ state="random", wall="all" });
+                                                      end
+                                                   end
+                                       });
+                                    end
+                                    des.door({ state="random", wall="all" });
+                                    if (percent(15)) then
+                                       des.door({ state="random", wall="all" });
+                                    end
+                                 end
+                     });
+                  end
+         });
+      end,
+   },
+
+   {
+      name = "Default room with themed fill",
       frequency = 6,
       contents = function()
          des.room({ type = "themed", contents = themeroom_fill });
@@ -324,6 +371,7 @@ themerooms = {
    },
 
    {
+      name = "Unlit room with themed fill",
       frequency = 2,
       contents = function()
          des.room({ type = "themed", lit = 0, contents = themeroom_fill });
@@ -331,71 +379,79 @@ themerooms = {
    },
 
    {
+      name = "Room with both normal contents and themed fill",
       frequency = 2,
       contents = function()
          des.room({ type = "themed", filled = 1, contents = themeroom_fill });
       end
    },
 
-   -- Pillars
-   function()
-      des.room({ type = "themed", w = 10, h = 10,
-                 contents = function(rm)
-                    local terr = { "-", "-", "-", "-", "L", "P", "T" };
-                    shuffle(terr);
-                    for x = 0, (rm.width / 4) - 1 do
-                       for y = 0, (rm.height / 4) - 1 do
-                          des.terrain({ x = x * 4 + 2, y = y * 4 + 2, typ = terr[1], lit = -2 });
-                          des.terrain({ x = x * 4 + 3, y = y * 4 + 2, typ = terr[1], lit = -2 });
-                          des.terrain({ x = x * 4 + 2, y = y * 4 + 3, typ = terr[1], lit = -2 });
-                          des.terrain({ x = x * 4 + 3, y = y * 4 + 3, typ = terr[1], lit = -2 });
-                       end
-                    end
-                 end
-      });
-   end,
+   {
+      name = 'Pillars',
+      contents = function()
+         des.room({ type = "themed", w = 10, h = 10,
+                  contents = function(rm)
+                     local terr = { "-", "-", "-", "-", "L", "P", "T" };
+                     shuffle(terr);
+                     for x = 0, (rm.width / 4) - 1 do
+                        for y = 0, (rm.height / 4) - 1 do
+                           des.terrain({ x = x * 4 + 2, y = y * 4 + 2, typ = terr[1], lit = -2 });
+                           des.terrain({ x = x * 4 + 3, y = y * 4 + 2, typ = terr[1], lit = -2 });
+                           des.terrain({ x = x * 4 + 2, y = y * 4 + 3, typ = terr[1], lit = -2 });
+                           des.terrain({ x = x * 4 + 3, y = y * 4 + 3, typ = terr[1], lit = -2 });
+                        end
+                     end
+                  end
+         });
+      end,
+   },
 
-   -- Mausoleum
-   function()
-      des.room({ type = "themed", w = 5 + nh.rn2(3)*2, h = 5 + nh.rn2(3)*2,
-                 contents = function(rm)
-                    des.room({ type = "themed",
-			       x = (rm.width - 1) / 2, y = (rm.height - 1) / 2,
-			       w = 1, h = 1, joined = false,
-                               contents = function()
-                                  if (percent(50)) then
-                                     local mons = { "M", "V", "L", "Z" };
-                                     shuffle(mons);
-                                     des.monster({ class = mons[1], x=0,y=0, waiting = 1 });
-                                  else
-                                     des.object({ id = "corpse", montype = "@", coord = {0,0} });
-                                  end
-                                  if (percent(20)) then
-                                     des.door({ state="secret", wall="all" });
-                                  end
-                               end
-                    });
-                 end
-      });
-   end,
+   {
+      name = 'Mausoleum',
+      contents = function()
+         des.room({ type = "themed", w = 5 + nh.rn2(3)*2, h = 5 + nh.rn2(3)*2,
+                  contents = function(rm)
+                     des.room({ type = "themed",
+                                 x = (rm.width - 1) / 2, y = (rm.height - 1) / 2,
+                                 w = 1, h = 1, joined = false,
+                                 contents = function()
+                                    if (percent(50)) then
+                                       local mons = { "M", "V", "L", "Z" };
+                                       shuffle(mons);
+                                       des.monster({ class = mons[1], x=0,y=0, waiting = 1 });
+                                    else
+                                       des.object({ id = "corpse", montype = "@", coord = {0,0} });
+                                    end
+                                    if (percent(20)) then
+                                       des.door({ state="secret", wall="all" });
+                                    end
+                                 end
+                     });
+                  end
+         });
+      end,
+   },
 
-   -- Random dungeon feature in the middle of an odd-sized room
-   function()
-      local wid = 3 + (nh.rn2(3) * 2);
-      local hei = 3 + (nh.rn2(3) * 2);
-      des.room({ type = "ordinary", filled = 1, w = wid, h = hei,
-                 contents = function(rm)
-                    local feature = { "C", "L", "I", "P", "T" };
-                    shuffle(feature);
-                    des.terrain((rm.width - 1) / 2, (rm.height - 1) / 2,
-				feature[1]);
-                 end
-      });
-   end,
+   {
+      name = 'Random dungeon feature in the middle of an odd-sized room',
+      contents = function()
+         local wid = 3 + (nh.rn2(3) * 2);
+         local hei = 3 + (nh.rn2(3) * 2);
+         des.room({ type = "ordinary", filled = 1, w = wid, h = hei,
+                  contents = function(rm)
+                     local feature = { "C", "L", "I", "P", "T" };
+                     shuffle(feature);
+                     des.terrain((rm.width - 1) / 2, (rm.height - 1) / 2,
+                                 feature[1]);
+                  end
+         });
+      end,
+   },
 
-   -- L-shaped
-   function()
-      des.map({ map = [[
+   {
+      name = 'L-shaped',
+      contents = function()
+         des.map({ map = [[
 -----xxx
 |...|xxx
 |...|xxx
@@ -404,11 +460,13 @@ themerooms = {
 |......|
 |......|
 --------]], contents = function(m) filler_region(1,1); end });
-   end,
+      end,
+   },
 
-   -- L-shaped, rot 1
-   function()
-      des.map({ map = [[
+   {
+      name = 'L-shaped, rot 1',
+      contents = function()
+         des.map({ map = [[
 xxx-----
 xxx|...|
 xxx|...|
@@ -417,11 +475,13 @@ xxx|...|
 |......|
 |......|
 --------]], contents = function(m) filler_region(5,1); end });
-   end,
+      end,
+   },
 
-   -- L-shaped, rot 2
-   function()
-      des.map({ map = [[
+   {
+      name = 'L-shaped, rot 2',
+      contents = function()
+         des.map({ map = [[
 --------
 |......|
 |......|
@@ -430,11 +490,13 @@ xxx|...|
 xxx|...|
 xxx|...|
 xxx-----]], contents = function(m) filler_region(1,1); end });
-   end,
+      end,
+   },
 
-   -- L-shaped, rot 3
-   function()
-      des.map({ map = [[
+   {
+      name = 'L-shaped, rot 3',
+      contents = function()
+         des.map({ map = [[
 --------
 |......|
 |......|
@@ -443,11 +505,13 @@ xxx-----]], contents = function(m) filler_region(1,1); end });
 |...|xxx
 |...|xxx
 -----xxx]], contents = function(m) filler_region(1,1); end });
-   end,
+      end,
+   },
 
-   -- Blocked center
-   function()
-      des.map({ map = [[
+   {
+      name = 'Blocked center',
+      contents = function()
+         des.map({ map = [[
 -----------
 |.........|
 |.........|
@@ -459,18 +523,20 @@ xxx-----]], contents = function(m) filler_region(1,1); end });
 |.........|
 |.........|
 -----------]], contents = function(m)
-if (percent(30)) then
-   local terr = { "-", "P" };
-   shuffle(terr);
-   des.replace_terrain({ region = {1,1, 9,9}, fromterrain = "L", toterrain = terr[1] });
-end
-filler_region(1,1);
-end });
-   end,
+            if (percent(30)) then
+               local terr = { "-", "P" };
+               shuffle(terr);
+               des.replace_terrain({ region = {1,1, 9,9}, fromterrain = "L", toterrain = terr[1] });
+            end
+            filler_region(1,1);
+         end });
+      end,
+   },
 
-   -- Circular, small
-   function()
-      des.map({ map = [[
+   {
+      name = 'Circular, small',
+      contents = function()
+         des.map({ map = [[
 xx---xx
 x--.--x
 --...--
@@ -478,11 +544,13 @@ x--.--x
 --...--
 x--.--x
 xx---xx]], contents = function(m) filler_region(3,3); end });
-   end,
+      end,
+   },
 
-   -- Circular, medium
-   function()
-      des.map({ map = [[
+   {
+      name = 'Circular, medium',
+      contents = function()
+         des.map({ map = [[
 xx-----xx
 x--...--x
 --.....--
@@ -492,11 +560,13 @@ x--...--x
 --.....--
 x--...--x
 xx-----xx]], contents = function(m) filler_region(4,4); end });
-   end,
+      end,
+   },
 
-   -- Circular, big
-   function()
-      des.map({ map = [[
+   {
+      name = 'Circular, big',
+      contents = function()
+         des.map({ map = [[
 xxx-----xxx
 x---...---x
 x-.......-x
@@ -508,11 +578,13 @@ x-.......-x
 x-.......-x
 x---...---x
 xxx-----xxx]], contents = function(m) filler_region(5,5); end });
-   end,
+      end,
+   },
 
-   -- T-shaped
-   function()
-      des.map({ map = [[
+   {
+      name = 'T-shaped',
+      contents = function()
+         des.map({ map = [[
 xxx-----xxx
 xxx|...|xxx
 xxx|...|xxx
@@ -521,11 +593,13 @@ xxx|...|xxx
 |.........|
 |.........|
 -----------]], contents = function(m) filler_region(5,5); end });
-   end,
+      end,
+   },
 
-   -- T-shaped, rot 1
-   function()
-      des.map({ map = [[
+   {
+      name = 'T-shaped, rot 1',
+      contents = function()
+         des.map({ map = [[
 -----xxx
 |...|xxx
 |...|xxx
@@ -537,11 +611,13 @@ xxx|...|xxx
 |...|xxx
 |...|xxx
 -----xxx]], contents = function(m) filler_region(2,2); end });
-   end,
+      end,
+   },
 
-   -- T-shaped, rot 2
-   function()
-      des.map({ map = [[
+   {
+      name = 'T-shaped, rot 2',
+      contents = function()
+         des.map({ map = [[
 -----------
 |.........|
 |.........|
@@ -550,11 +626,13 @@ xxx|...|xxx
 xxx|...|xxx
 xxx|...|xxx
 xxx-----xxx]], contents = function(m) filler_region(2,2); end });
-   end,
+      end,
+   },
 
-   -- T-shaped, rot 3
-   function()
-      des.map({ map = [[
+   {
+      name = 'T-shaped, rot 3',
+      contents = function()
+         des.map({ map = [[
 xxx-----
 xxx|...|
 xxx|...|
@@ -566,11 +644,13 @@ xxx|...|
 xxx|...|
 xxx|...|
 xxx-----]], contents = function(m) filler_region(5,5); end });
-   end,
+      end,
+   },
 
-   -- S-shaped
-   function()
-      des.map({ map = [[
+   {
+      name = 'S-shaped',
+      contents = function()
+         des.map({ map = [[
 -----xxx
 |...|xxx
 |...|xxx
@@ -582,11 +662,13 @@ xxx-----]], contents = function(m) filler_region(5,5); end });
 xxx|...|
 xxx|...|
 xxx-----]], contents = function(m) filler_region(2,2); end });
-   end,
+      end,
+   },
 
-   -- S-shaped, rot 1
-   function()
-      des.map({ map = [[
+   {
+      name = 'S-shaped, rot 1',
+      contents = function()
+         des.map({ map = [[
 xxx--------
 xxx|......|
 xxx|......|
@@ -595,11 +677,13 @@ xxx|......|
 |......|xxx
 |......|xxx
 --------xxx]], contents = function(m) filler_region(5,5); end });
-   end,
+      end,
+   },
 
-   -- Z-shaped
-   function()
-      des.map({ map = [[
+   {
+      name = 'Z-shaped',
+      contents = function()
+         des.map({ map = [[
 xxx-----
 xxx|...|
 xxx|...|
@@ -611,11 +695,13 @@ xxx|...|
 |...|xxx
 |...|xxx
 -----xxx]], contents = function(m) filler_region(5,5); end });
-   end,
+      end,
+   },
 
-   -- Z-shaped, rot 1
-   function()
-      des.map({ map = [[
+   {
+      name = 'Z-shaped, rot 1',
+      contents = function()
+         des.map({ map = [[
 --------xxx
 |......|xxx
 |......|xxx
@@ -624,11 +710,13 @@ xxx|...|
 xxx|......|
 xxx|......|
 xxx--------]], contents = function(m) filler_region(2,2); end });
-   end,
+      end,
+   },
 
-   -- Cross
-   function()
-      des.map({ map = [[
+   {
+      name = 'Cross',
+      contents = function()
+         des.map({ map = [[
 xxx-----xxx
 xxx|...|xxx
 xxx|...|xxx
@@ -640,11 +728,13 @@ xxx|...|xxx
 xxx|...|xxx
 xxx|...|xxx
 xxx-----xxx]], contents = function(m) filler_region(6,6); end });
-   end,
+      end,
+   },
 
-   -- Four-leaf clover
-   function()
-      des.map({ map = [[
+   {
+      name = 'Four-leaf clover',
+      contents = function()
+         des.map({ map = [[
 -----x-----
 |...|x|...|
 |...---...|
@@ -656,59 +746,63 @@ xx|.....|xx
 |...---...|
 |...|x|...|
 -----x-----]], contents = function(m) filler_region(6,6); end });
-   end,
+      end,
+   },
 
-   -- Water-surrounded vault
-   function()
-      des.map({ map = [[
+   {
+      name = 'Water-surrounded vault',
+      contents = function()
+         des.map({ map = [[
 }}}}}}
 }----}
 }|..|}
 }|..|}
 }----}
 }}}}}}]], contents = function(m) des.region({ region={3,3,3,3}, type="themed", irregular=true, filled=0, joined=false });
-     local nasty_undead = { "giant zombie", "ettin zombie", "vampire lord" };
-     local chest_spots = { { 2, 2 }, { 3, 2 }, { 2, 3 }, { 3, 3 } };
+            local nasty_undead = { "giant zombie", "ettin zombie", "vampire lord" };
+            local chest_spots = { { 2, 2 }, { 3, 2 }, { 2, 3 }, { 3, 3 } };
 
-     shuffle(chest_spots)
-     -- Guarantee an escape item inside one of the chests, to prevent the hero
-     -- falling in from above and becoming permanently stuck
-     -- [cf. generate_way_out_method(sp_lev.c)].
-     -- If the escape item is made of glass or crystal, make sure that the
-     -- chest isn't locked so that kicking it to gain access to its contents
-     -- won't be necessary; otherwise retain lock state from random creation.
-     -- "pick-axe", "dwarvish mattock" could be included in the list of escape
-     -- items but don't normally generate in containers.
-     local escape_items = {
-        "scroll of teleportation", "ring of teleportation",
-        "wand of teleportation", "wand of digging"
-     };
-     local itm = obj.new(escape_items[math.random(#escape_items)]);
-     local itmcls = itm:class()
-     local box
-     if itmcls[ "material" ] == "glass" then
-         -- explicitly force chest to be unlocked
-	 box = des.object({ id = "chest", coord = chest_spots[1],
-                            olocked = "no" });
-     else
-         -- accept random locked/unlocked state
-	 box = des.object({ id = "chest", coord = chest_spots[1] });
-     end;
-     box:addcontent(itm);
+            shuffle(chest_spots)
+            -- Guarantee an escape item inside one of the chests, to prevent the
+            -- hero falling in from above and becoming permanently stuck
+            -- [cf. generate_way_out_method(sp_lev.c)].
+            -- If the escape item is made of glass or crystal, make sure that
+            -- the chest isn't locked so that kicking it to gain access to its
+            -- contents won't be necessary; otherwise retain lock state from
+            -- random creation.
+            -- "pick-axe", "dwarvish mattock" could be included in the list of
+            -- escape items but don't normally generate in containers.
+            local escape_items = {
+               "scroll of teleportation", "ring of teleportation",
+               "wand of teleportation", "wand of digging"
+            };
+            local itm = obj.new(escape_items[math.random(#escape_items)]);
+            local itmcls = itm:class()
+            local box
+            if itmcls[ "material" ] == "glass" then
+                  -- explicitly force chest to be unlocked
+                  box = des.object({ id = "chest", coord = chest_spots[1],
+                                    olocked = "no" });
+            else
+                  -- accept random locked/unlocked state
+                  box = des.object({ id = "chest", coord = chest_spots[1] });
+            end;
+            box:addcontent(itm);
 
-     for i = 2, #chest_spots do
-         des.object({ id = "chest", coord = chest_spots[i] });
-     end
+            for i = 2, #chest_spots do
+                  des.object({ id = "chest", coord = chest_spots[i] });
+            end
 
-     shuffle(nasty_undead);
-     des.monster(nasty_undead[1], 2, 2);
-     des.exclusion({ type = "teleport", region = { 2,2, 3,3 } });
-end });
-   end,
+            shuffle(nasty_undead);
+            des.monster(nasty_undead[1], 2, 2);
+            des.exclusion({ type = "teleport", region = { 2,2, 3,3 } });
+         end });
+      end,
+   },
 
-   -- Twin businesses
    {
-      mindiff = 4; -- arbitrary
+      name = 'Twin businesses',
+      mindiff = 4, -- arbitrary
       contents = function()
          -- Due to the way room connections work in mklev.c, we must guarantee
          -- that the "aisle" between the shops touches all four walls of the
@@ -761,7 +855,14 @@ end });
 
 };
 
+-- store these at global scope, they will be reinitialized in
+-- pre_themerooms_generate
+debug_rm_idx = nil
+debug_fill_idx = nil
 
+-- Given a point in a themed room, ensure that themed room is stocked with
+-- regular room contents.
+-- With 30% chance, also give it a random themed fill.
 function filler_region(x, y)
    local rmtyp = "ordinary";
    local func = nil;
@@ -775,31 +876,76 @@ end
 function is_eligible(room, mkrm)
    local t = type(room);
    local diff = nh.level_difficulty();
-   if (t == "table") then
-      if (room.mindiff ~= nil and diff < room.mindiff) then
-         return false
-      elseif (room.maxdiff ~= nil and diff > room.maxdiff) then
-         return false
-      end
-      if (mkrm ~= nil and room.eligible ~= nil) then
-         return room.eligible(mkrm);
-      end
-   elseif (t == "function") then
-      -- functions currently have no constraints
+   if (room.mindiff ~= nil and diff < room.mindiff) then
+      return false
+   elseif (room.maxdiff ~= nil and diff > room.maxdiff) then
+      return false
+   end
+   if (mkrm ~= nil and room.eligible ~= nil) then
+      return room.eligible(mkrm);
    end
    return true
 end
 
+-- given the name of a themed room or fill, return its index in that array
+function lookup_by_name(name, checkfills)
+   if name == nil then
+      return nil
+   end
+   if checkfills then
+      for i = 1, #themeroom_fills do
+         if themeroom_fills[i].name == name then
+            return i
+         end
+      end
+   else
+      for i = 1, #themerooms do
+         if themerooms[i].name == name then
+            return i
+         end
+      end
+   end
+   return nil
+end
+
 -- called repeatedly until the core decides there are enough rooms
 function themerooms_generate()
+   if debug_rm_idx ~= nil then
+      -- room may not be suitable for stairs/portals, so create the "default"
+      -- room half of the time
+      -- (if the user specified BOTH a room and a fill, presumably they are
+      -- interested in what happens when that room gets that fill, so don't
+      -- bother generating default-with-fill rooms as happens below)
+      local actualrm = lookup_by_name("default", false);
+      if percent(50) then
+         if is_eligible(themerooms[debug_rm_idx]) then
+            actualrm = debug_rm_idx
+         else
+            pline("Warning: themeroom '"..themerooms[debug_rm_idx].name
+                  .."' is ineligible")
+         end
+      end
+      themerooms[actualrm].contents();
+      return
+   elseif debug_fill_idx ~= nil then
+      -- when a fill is requested but not a room, still create the "default"
+      -- room half of the time, and "default with themed fill" half of the time
+      -- (themeroom_fill will take care of guaranteeing the fill in it)
+      local actualrm = lookup_by_name(percent(50) and "Default room with themed fill"
+                                                  or "default")
+      themerooms[actualrm].contents();
+      return
+   end
    local pick = 1;
    local total_frequency = 0;
    for i = 1, #themerooms do
-      -- Reservoir sampling: select one room from the set of eligible rooms,
-      -- which may change on different levels because of level difficulty.
-      if is_eligible(themerooms[i], nil) then
+      if (type(themerooms[i]) ~= "table") then
+         nh.impossible('themed room '..i..' is not a table')
+      elseif is_eligible(themerooms[i], nil) then
+         -- Reservoir sampling: select one room from the set of eligible rooms,
+         -- which may change on different levels because of level difficulty.
          local this_frequency;
-         if (type(themerooms[i]) == "table" and themerooms[i].frequency ~= nil) then
+         if (themerooms[i].frequency ~= nil) then
             this_frequency = themerooms[i].frequency;
          else
             this_frequency = 1;
@@ -811,17 +957,23 @@ function themerooms_generate()
          end
       end
    end
-
-   local t = type(themerooms[pick]);
-   if (t == "table") then
-      themerooms[pick].contents();
-   elseif (t == "function") then
-      themerooms[pick]();
-   end
+   themerooms[pick].contents();
 end
 
 -- called before any rooms are generated
 function pre_themerooms_generate()
+   local debug_themerm = nh.debug_themerm(false)
+   local debug_fill = nh.debug_themerm(true)
+   debug_rm_idx = lookup_by_name(debug_themerm, false)
+   debug_fill_idx = lookup_by_name(debug_fill, true)
+   if debug_themerm ~= nil and debug_rm_idx == nil then
+      pline("Warning: themeroom '"..debug_themerm
+            .."' not found in themerooms", true)
+   end
+   if debug_fill ~= nil and debug_fill_idx == nil then
+      pline("Warning: themeroom fill '"..debug_fill
+            .."' not found in themeroom_fills", true)
+   end
 end
 
 -- called after all rooms have been generated
@@ -830,32 +982,41 @@ function post_themerooms_generate()
 end
 
 function themeroom_fill(rm)
+   if debug_fill_idx ~= nil then
+      if is_eligible(themeroom_fills[debug_fill_idx], rm) then
+         themeroom_fills[debug_fill_idx].contents(rm);
+      else
+         -- ideally this would be a debugpline, not a full pline, and offer
+         -- some more context on whether it failed because of difficulty or
+         -- because of eligible function returning false; the warning doesn't
+         -- necessarily mean anything.
+         pline("Warning: fill '"..themeroom_fills[debug_fill_idx].name
+               .."' is not eligible in room that generated it")
+      end
+      return
+   end
    local pick = 1;
    local total_frequency = 0;
    for i = 1, #themeroom_fills do
-      -- Reservoir sampling: select one room from the set of eligible rooms,
-      -- which may change on different levels because of level difficulty.
-      if is_eligible(themeroom_fills[i], rm) then
+      if (type(themeroom_fills[i]) ~= "table") then
+         nh.impossible('themeroom fill '..i..' must be a table')
+      elseif is_eligible(themeroom_fills[i], rm) then
+         -- Reservoir sampling: select one room from the set of eligible rooms,
+         -- which may change on different levels because of level difficulty.
          local this_frequency;
-         if (type(themeroom_fills[i]) == "table" and themeroom_fills[i].frequency ~= nil) then
+         if (themeroom_fills[i].frequency ~= nil) then
             this_frequency = themeroom_fills[i].frequency;
          else
             this_frequency = 1;
          end
          total_frequency = total_frequency + this_frequency;
-         -- avoid rn2(0) if a room has freq 0
+         -- avoid rn2(0) if a fill has freq 0
          if this_frequency > 0 and nh.rn2(total_frequency) < this_frequency then
             pick = i;
          end
       end
    end
-
-   local t = type(themeroom_fills[pick]);
-   if (t == "table") then
-      themeroom_fills[pick].contents(rm);
-   elseif (t == "function") then
-      themeroom_fills[pick](rm);
-   end
+   themeroom_fills[pick].contents(rm);
 end
 
 -- postprocess callback: create an engraving pointing at a location
diff --git a/src/nhlua.c b/src/nhlua.c
index 6342f949c..10c67494a 100644
--- a/src/nhlua.c
+++ b/src/nhlua.c
@@ -65,6 +65,7 @@ staticfn int nhl_rn2(lua_State *);
 staticfn int nhl_random(lua_State *);
 staticfn int nhl_level_difficulty(lua_State *);
 staticfn int nhl_is_genocided(lua_State *);
+staticfn int nhl_get_debug_themerm_name(lua_State *);
 staticfn void init_nhc_data(lua_State *);
 staticfn int nhl_push_anything(lua_State *, int, void *);
 staticfn int nhl_meta_u_index(lua_State *);
@@ -975,6 +976,30 @@ nhl_is_genocided(lua_State *L)
     return 1;
 }
 
+/* local debug_themerm = nh.debug_themerm(isfill)
+ * if isfill is false, returns value of env variable THEMERM
+ * if isfill is true,  returns value of env variable THEMERMFILL
+ * return nil if not in wizard mode or the variable isn't set */
+staticfn int
+nhl_get_debug_themerm_name(lua_State *L)
+{
+    int argc = lua_gettop(L);
+    if (argc == 1) {
+        char *dbg_themerm = (char *) 0;
+        boolean is_fill = lua_toboolean(L, 1);
+        lua_pop(L, 1);
+        if (wizard)
+            dbg_themerm = getenv(is_fill ? "THEMERMFILL" : "THEMERM");
+        if (!dbg_themerm || strlen(dbg_themerm) == 0) {
+            lua_pushnil(L);
+        } else {
+            lua_pushstring(L, dbg_themerm);
+        }
+    } else {
+        nhl_error(L, "debug_themerm should have 1 boolean arg");
+    }
+    return 1;
+}
 
 RESTORE_WARNING_UNREACHABLE_CODE
 
@@ -1754,6 +1779,7 @@ static const struct luaL_Reg nhl_functions[] = {
     { "random", nhl_random },
     { "level_difficulty", nhl_level_difficulty },
     { "is_genocided", nhl_is_genocided },
+    { "debug_themerm", nhl_get_debug_themerm_name },
     { "parse_config", nhl_parse_config },
     { "get_config", nhl_get_config },
     { "get_config_errors", l_get_config_errors },