diff --git a/polymer/eduke32/source/gamedef.c b/polymer/eduke32/source/gamedef.c
index 6b65a3a47..3c7edf42a 100644
--- a/polymer/eduke32/source/gamedef.c
+++ b/polymer/eduke32/source/gamedef.c
@@ -695,6 +695,7 @@ const char *EventNames[MAXEVENTS] =
     "EVENT_SAVEGAME",
     "EVENT_PREGAME",
     "EVENT_CHANGEMENU",
+    "EVENT_DAMAGEHPLANE",
 #ifdef LUNATIC
     "EVENT_ANIMATEALLSPRITES",
 #endif
diff --git a/polymer/eduke32/source/gameexec.h b/polymer/eduke32/source/gameexec.h
index 9d750e539..234a11f49 100644
--- a/polymer/eduke32/source/gameexec.h
+++ b/polymer/eduke32/source/gameexec.h
@@ -125,8 +125,9 @@ enum GameEvent_t {
     EVENT_SAVEGAME,
     EVENT_PREGAME,
     EVENT_CHANGEMENU,
+    EVENT_DAMAGEHPLANE,  // 95
 #ifdef LUNATIC
-    EVENT_ANIMATEALLSPRITES,  // 95
+    EVENT_ANIMATEALLSPRITES,
 #endif
     MAXEVENTS
 };
diff --git a/polymer/eduke32/source/lunatic/con_lang.lua b/polymer/eduke32/source/lunatic/con_lang.lua
index 67c9d3fb4..536ce2f99 100644
--- a/polymer/eduke32/source/lunatic/con_lang.lua
+++ b/polymer/eduke32/source/lunatic/con_lang.lua
@@ -17,7 +17,7 @@ MAXGAMETYPES = 16
 
 MAXSKILLS = 7
 
-MAXEVENTS = 95  -- KEEPINSYNC with EVENT_* list
+MAXEVENTS = 96  -- KEEPINSYNC with EVENT_* list
 MAXSOUNDS = 4096
 
 MAXSESSIONVARS = 8  -- KEEPINSYNC lunatic_game.c
@@ -170,7 +170,8 @@ EVENT = {
     EVENT_SAVEGAME = 92,
     EVENT_PREGAME = 93,
     EVENT_CHANGEMENU = 94,
---    EVENT_ANIMATEALLSPRITES = 95,  -- internal
+    EVENT_DAMAGEHPLANE = 95,
+--    EVENT_ANIMATEALLSPRITES = 96,  -- internal
 }
 
 -- NOTE: negated values are not exported to the ffi.C namespace or CON.
diff --git a/polymer/eduke32/source/lunatic/control.lua b/polymer/eduke32/source/lunatic/control.lua
index 357cadda4..95750e060 100644
--- a/polymer/eduke32/source/lunatic/control.lua
+++ b/polymer/eduke32/source/lunatic/control.lua
@@ -272,6 +272,8 @@ end
 function insertsprite(tab_or_tilenum, ...)
     local tilenum, pos, sectnum  -- mandatory
     -- optional with defaults:
+    -- TODO: swap order of owner and statnum?
+    -- XXX: owner -1 valid???
     local owner, statnum
     local shade, xrepeat, yrepeat, ang, xvel, zvel = 0, 48, 48, 0, 0, 0
 
diff --git a/polymer/eduke32/source/lunatic/defs.ilua b/polymer/eduke32/source/lunatic/defs.ilua
index 58abf56b5..e79f81e4f 100644
--- a/polymer/eduke32/source/lunatic/defs.ilua
+++ b/polymer/eduke32/source/lunatic/defs.ilua
@@ -2091,7 +2091,7 @@ local function our_gameactor(args)
 
         -- Register our EVENT_ANIMATEALLSPRITES only now so that it is not
         -- called if there are no 'animate' definitions.
-        gameevent_internal(95, animate_all_sprites)  -- EVENT_ANIMATEALLSPRITES
+        gameevent_internal(96, animate_all_sprites)  -- EVENT_ANIMATEALLSPRITES
     end
 
     -- All good, set the tile bits in initial run and register the actor!
diff --git a/polymer/eduke32/source/lunatic/defs_common.lua b/polymer/eduke32/source/lunatic/defs_common.lua
index 00cb8c49e..c7e0f75ce 100644
--- a/polymer/eduke32/source/lunatic/defs_common.lua
+++ b/polymer/eduke32/source/lunatic/defs_common.lua
@@ -884,7 +884,7 @@ static_members.sector.STAT = conststruct
     TRANS2 = 128,
     TRANS1 = 256,
     BLOCK = 512,
-    HITSCAN = 1024,
+    HITSCAN = 2048,
 
     FLIP_BITMASK = 16+32,
     ORIENT_BITMASK = 4+16+32,
@@ -936,6 +936,8 @@ static_members.sprite.CSTAT = conststruct
 
     ALIGN_BITMASK = 16+32,
     TRANS_BITMASK = 2+512,
+
+    INVISIBLE = 32768,
 }
 
 local bitar = require("bitar")
@@ -944,6 +946,19 @@ local bitar = require("bitar")
 -- machines. This sucks.
 static_members.sector.showbitmap = bitar.new(ffiC.MAXSECTORS-1, ffi.cast("int32_t *", ffiC.show2dsector))
 
+static_members.sector.DAMAGEHPLANE = conststruct
+{
+    SUPPRESS = -1,
+    DEFAULT = 0,
+    GLASSBREAK = 2^20,
+}
+
+function static_members.sector.damagehplane_whatsect(RETURN)
+    local what = (band(RETURN, 65536)~=0) and "ceiling" or "floor"
+    local sectnum = band(RETURN, ffiC.MAXSECTORS-1)
+    return what, sectnum
+end
+
 local function iter_allsprites(_, curi)
     for i=curi+1,ffiC.MAXSPRITES-1 do
         if (ffiC.sprite[i].statnum ~= ffiC.MAXSTATUS) then
diff --git a/polymer/eduke32/source/lunatic/doc/lunatic.txt b/polymer/eduke32/source/lunatic/doc/lunatic.txt
index fa9d7e91d..43ca7e222 100644
--- a/polymer/eduke32/source/lunatic/doc/lunatic.txt
+++ b/polymer/eduke32/source/lunatic/doc/lunatic.txt
@@ -942,7 +942,7 @@ sprite by `zofs` units''.
 Provides a mapping of symbolic names to values applicable to
 <<sprite_cstat,`sprite[i].cstat`>>.  These name single bits:
 `BLOCK`, `TRANS1`, `XFLIP`, `YFLIP`, `ALIGNWALL`, `ALIGNFLOOR`, `ONESIDE`,
-`CENTER`, `HITSCAN`, `TRANS2`,
+`CENTER`, `HITSCAN`, `TRANS2`, `INVISIBLE`,
 while the following denote _bit masks_: `ALIGN_BITMASK`, `TRANS_BITMASK`.
 
 ===== `spriteext`
@@ -2232,6 +2232,45 @@ cheat give a different ``full'' amount. A negative value is ignored.
 `CHEATGETSTEROIDS`, `CHEATGETHEAT`, `CHEATGETBOOT`, `CHEATGETSHIELD`,
 `CHEATGETSCUBA`, `CHEATGETHOLODUKE`, `CHEATGETJETPACK`, `CHEATGETFIRSTAID`.
 
+[float]
+`EVENT_DAMAGEHPLANE`
+~~~~~~~~~~~~~~~~~~~~
+
+Triggered when a ceiling or a floor (collectively called ``hplane'') is
+determined as being damaged. The event receives `RETURN` as a value that can be
+decoded into two parts by passing it to `sector.damagehplane_whatsect`:
+
+[source]
+----------
+local what, sectnum = sector.damagehplane_whatsect(gv.RETURN)
+----------
+Then,
+
+* `what` is one of the strings `'ceiling'` or `'floor'` and
+* `sectnum` is the sector whose hplane is considered to be damaged.
+
+When `EVENT_DAMAGEHPLANE` is left, `RETURN` is examined to determine the
+further action. It may be one of three values given by `sector.DAMAGEHPLANE`
+(abbreviated `DHP` in the following):
+
+* `DHP.SUPPRESS`: the hard-wired code that would subsequently be run is
+  suppressed entirely
+
+* `DHP.DEFAULT`: The default code for hplane damaging is run. For floors, it
+  does nothing. For ceilings, it checks whether it has a tile number in a
+  hard-coded set of values depicting a breakable light. In that case, the tile
+  number is changed to the ``broken'' version and a ``glass breaking'' effect
+  consisting of playing a sound and spawning glass sprites is started. Also,
+  certain code related to SE3 and SE12 effects is run.
+
+* `DHP.GLASSBREAK`: The light-breaking effect described above is run
+  unconditionally, but *without* changing the hplane's tile number, which is
+  assumed to have been done by the event.
+
+If value last assigned to `RETURN` is not one in the above-mentioned set when
+`EVENT_DAMAGEHPLANE` is left, the behavior is undefined.
+
+
 [float]
 TODO
 ~~~~
diff --git a/polymer/eduke32/source/lunatic/test/damagehplane.lua b/polymer/eduke32/source/lunatic/test/damagehplane.lua
new file mode 100644
index 000000000..a30017c33
--- /dev/null
+++ b/polymer/eduke32/source/lunatic/test/damagehplane.lua
@@ -0,0 +1,105 @@
+
+local bit = require("bit")
+local band = bit.band
+
+local tostring = tostring
+
+local gv = gv
+local actor = actor
+local sector, wall, sprite = sector, wall, sprite
+
+local printf = printf
+local sectorsofbunch = sectorsofbunch
+
+local con = require("con")
+
+local D = require("CON.DEFS")
+
+----------
+
+local TROR_GLASSBREAKER = 2959  -- red 'T'
+-- Actor controlling the timing of a TROR hplane breaking.
+gameactor
+{
+    TROR_GLASSBREAKER,
+
+    function(aci, pli, dist)
+        local spr = sprite[aci]
+        if (not (spr.lotag == 712 and spr.hitag == 119)) then  -- check BREAKER_MAGIC
+            sprite.changestat(aci, actor.STAT.DEFAULT)
+            return
+        end
+
+        local cnt = actor[aci]:get_count()
+        local finish = (cnt >= 6)
+
+        if (cnt == 0) then
+            -- NOTE: INTERNAL interface, DON'T USE!
+            con._sound(aci, D.GLASS_BREAKING)
+        end
+
+        local bunchnum = spr.extra
+        for sectnum, what in sectorsofbunch(bunchnum, gv.BOTH_CF) do
+            local cf = sector[sectnum][what]
+
+            -- TODO: provide cf:set_picnum()
+            if (what=="ceiling") then
+                sector[sectnum]:set_ceilingpicnum(D.GLASS2 + cnt)
+            else
+                sector[sectnum]:set_floorpicnum(D.GLASS2 + cnt)
+            end
+
+            cf.statbits:clear(sector.STAT.BLOCK + sector.STAT.HITSCAN)
+            if (finish) then
+                cf.statbits:clear(sector.STAT.TRANS_BITMASK)
+            end
+        end
+
+        if (finish) then
+            con.killit()
+        end
+    end
+}
+
+
+local DHP = sector.DAMAGEHPLANE
+
+gameevent
+{
+    gv.EVENT_DAMAGEHPLANE,
+
+    function(aci, pli, dist)
+        local what, sectnum = sector.damagehplane_whatsect(gv.RETURN)
+        local sec = sector[sectnum]
+
+        -- Part I: make various screens breakable when it's a ceiling picnum.
+        if (what == "ceiling") then
+            -- hit ceiling
+            if (sec.ceilingpicnum >= 263 and sec.ceilingpicnum <= 275) then
+                sec:set_ceilingpicnum(D.W_SCREENBREAK + gv.krand()%3)
+                gv.RETURN = DHP.GLASSBREAK
+                return
+            end
+        end
+
+        -- Part II: breakable TROR hplanes
+        local cf = sec[what]
+--        printf("damage %s of sector %d (pic %d, bunch %d, hittable: %s)", what, sectnum,
+--               cf.picnum, cf.bunch, tostring(cf.statbits:test(sector.STAT.HITSCAN)))
+
+        if (cf.bunch >= 0 and (cf.picnum==198 or cf.picnum==D.GLASS2) and
+                cf.statbits:test(sector.STAT.HITSCAN)) then
+            local bi = con.insertsprite(TROR_GLASSBREAKER, wall[sec.wallptr], sectnum, aci, actor.STAT.ACTOR)
+            local breaker = sprite[bi]
+
+            breaker.cstat = sprite.CSTAT.INVISIBLE
+            breaker.lotag, breaker.hitag = 712, 119  -- BREAKER_MAGIC
+            breaker.extra = cf.bunch
+
+            gv.RETURN = DHP.SUPPRESS
+            return
+        end
+
+        gv.RETURN = DHP.DEFAULT
+    end
+}
diff --git a/polymer/eduke32/source/sector.c b/polymer/eduke32/source/sector.c
index 68d67a424..6b0bf4082 100644
--- a/polymer/eduke32/source/sector.c
+++ b/polymer/eduke32/source/sector.c
@@ -1874,13 +1874,27 @@ void A_DamageWall(int32_t spr,int32_t dawallnum,const vec3_t *pos,int32_t atwith
     }
 }
 
+// NOTE: return value never examined in any of the callers.
 int32_t Sect_DamageCeilingOrFloor(int32_t floorp, int32_t sn)
 {
     int32_t i, j;
 
+    const int32_t RETURN_in = floorp ? 131072+sn : 65536+sn;
+    int32_t ret = VM_OnEvent(EVENT_DAMAGEHPLANE, g_player[screenpeek].ps->i, screenpeek, -1, RETURN_in);
+
+    if (ret < 0)
+        return 0;
+
     if (floorp)
         return 0;
 
+    if (ret == (1<<20))
+    {
+        // Execute the hard-coded stuff without changing picnum (expected to
+        // have been done by the event).
+        goto GLASSBREAK_CODE;
+    }
+
     switch (DYNAMICTILEMAP(sector[sn].ceilingpicnum))
     {
     case WALLLIGHT1__STATIC:
@@ -1890,9 +1904,6 @@ int32_t Sect_DamageCeilingOrFloor(int32_t floorp, int32_t sn)
     case TECHLIGHT2__STATIC:
     case TECHLIGHT4__STATIC:
 
-        A_SpawnCeilingGlass(g_player[myconnectindex].ps->i,sn,10);
-        A_PlaySound(GLASS_BREAKING,g_player[screenpeek].ps->i);
-
         if (sector[sn].ceilingpicnum == WALLLIGHT1)
             sector[sn].ceilingpicnum = WALLLIGHTBUST1;
 
@@ -1911,6 +1922,9 @@ int32_t Sect_DamageCeilingOrFloor(int32_t floorp, int32_t sn)
         if (sector[sn].ceilingpicnum == TECHLIGHT4)
             sector[sn].ceilingpicnum = TECHLIGHTBUST4;
 
+    GLASSBREAK_CODE:
+        A_SpawnCeilingGlass(g_player[myconnectindex].ps->i,sn,10);
+        A_PlaySound(GLASS_BREAKING,g_player[screenpeek].ps->i);
 
         if (sector[sn].hitag == 0)
         {