diff --git a/Lua/classes.lua b/Lua/classes.lua
index 17d1337..78d07f6 100644
--- a/Lua/classes.lua
+++ b/Lua/classes.lua
@@ -8,6 +8,7 @@ local classes = {
     "Monitor",
     "ByteMonitor",
     "FlagMonitor",
+    "SceneFlagMonitor",
     "ActorLister",
     "InputHandler",
 }
diff --git a/Lua/classes/SceneFlagMonitor.lua b/Lua/classes/SceneFlagMonitor.lua
new file mode 100644
index 0000000..f698fc6
--- /dev/null
+++ b/Lua/classes/SceneFlagMonitor.lua
@@ -0,0 +1,19 @@
+local Monitor = require "classes.Monitor"
+local SceneFlagMonitor = Class(Monitor)
+
+function SceneFlagMonitor:mark(i, x, x1)
+    if not x1 then return end
+    local now = emu.framecount()
+    local diff = bit.bxor(x, x1)
+    for which = 0, 7 do
+        if bit.band(diff, 2^which) ~= 0 then
+            local state = bit.band(x, 2^which) ~= 0 and 1 or 0
+            local col = (3 - i)*8 + which
+            str = ('%s: %02i=%i'):format(self.name, col, state)
+            printf('%s  @%i', str, now)
+            message(str, 180)
+        end
+    end
+end
+
+return SceneFlagMonitor
diff --git a/Lua/scene flag monitor.lua b/Lua/scene flag monitor.lua
new file mode 100644
index 0000000..ceda019
--- /dev/null
+++ b/Lua/scene flag monitor.lua	
@@ -0,0 +1,44 @@
+require "boilerplate"
+require "addrs.init"
+require "classes"
+require "messages"
+
+local x1 = SceneFlagMonitor('x1', addrs.current_scene_flags_1)
+local x2 = SceneFlagMonitor('x2', addrs.current_scene_flags_2)
+local x3 = SceneFlagMonitor('x3', addrs.current_scene_flags_3)
+local x4 = SceneFlagMonitor('x4', addrs.current_scene_flags_4)
+local x5 = SceneFlagMonitor('x5', addrs.current_scene_flags_5)
+local scenes = {}
+local n1 = -1
+while mm or oot do
+    local n = addrs.scene_number()
+    if n ~= n1 then
+        if not scenes[n] then
+            scenes[n] = {}
+            printf('new scene %04X',n)--already has {TODO} flags', n)
+        end
+        if not scenes[n1] then
+            scenes[n1] = {}
+        end
+
+        scenes[n1][1] = x1.old_bytes
+        scenes[n1][2] = x2.old_bytes
+        scenes[n1][3] = x3.old_bytes
+        scenes[n1][4] = x4.old_bytes
+        scenes[n1][5] = x5.old_bytes
+        x1.old_bytes = scenes[n][1] or {}
+        x2.old_bytes = scenes[n][2] or {}
+        x3.old_bytes = scenes[n][3] or {}
+        x4.old_bytes = scenes[n][4] or {}
+        x5.old_bytes = scenes[n][5] or {}
+    end
+    n1 = n
+
+    x1:diff()
+    x2:diff()
+    x3:diff()
+    x4:diff()
+    x5:diff()
+    draw_messages()
+    emu.frameadvance()
+end