diff --git a/main.fs b/main.fs
index 8b3fd03..cd38be9 100644
--- a/main.fs
+++ b/main.fs
@@ -21,9 +21,15 @@ include debug.fs
 \ the word changed? leaves a -1 if the value has changed since last clear, 0 otherwise.
 : changed? ( addr offset -- flag ) cells + @ ;
 
-\ the variable "devices" holds the amount of devices currently in the pool. It has a change flag. It begins with the change flag set, to draw the screen the first time.
+\ the variable "devices" holds the amount of devices currently in the pool. It has two values a change flag. 
+\ The first value contains the current number of devices, the second contains the number of devices in the previous tick.
+\ (this is used to determine if the change flag needs to be set)
+\ It begins with the change flag set, to draw the screen the first time.
 \ this variable can contain decimal-point amounts of devices. Things that need a non-decimal amount can round it with ftrunc.
 create devices 0e f, -1 ,
+\ old devices is the old device count. For convenience.
+: old-devices devices float + ;
+
 \ the variable "base-devices/tick" is the base amount of devices added per tick.
 variable base-devices/tick
 0.0005e base-devices/tick f! 
@@ -48,9 +54,9 @@ S" you feel like throwing some stuff into the pool." set-message
 : f+! ( addr -- ) ( F: r -- ) dup f@ f+ f! ;
 
 \ any-change? leaves a -1 on the stack if any value has changed, 0 otherwise
-: any-change? ( -- flag ) membercost 1 changed? devices 1 changed? message 2 changed? or or ;
+: any-change? ( -- flag ) membercost 1 changed? devices 2 changed? message 2 changed? or or ;
 \ clear-all clears the change flag on all values.
-: clear-all membercost 1 cleared devices 1 cleared message 2 cleared ;
+: clear-all membercost 1 cleared devices 2 cleared message 2 cleared ;
 \ the word !0= tests if something is non-zero
 : !0= ( n -- flag ) 0= 0= ;
 \ the word f!0= tests if a floating thing is non-zero
@@ -88,13 +94,19 @@ S" you feel like throwing some stuff into the pool." set-message
 			1 count-messages-shown +!
 		then ;
 
+\ update-devices updates the device count, setting the change flag as needed
+: update-devices
+	devices f@ old-devices f! \ store old value of devices
+	devices/tick devices f+!
+	devices f@ ftrunc old-devices f@ ftrunc f= 0= if \ if devices has changed by an integer amount
+		devices 2 changed
+	then ;
+		 
+		
 \ the word game-tick runs a single tick of the game
 : game-tick unlock 
-		devices/tick devices f+! 
+		update-devices
 		set-count-message
-		\ TODO only set devices as changed on an integer change
-        \ this seems to somehow cause a float overflow lol
-		devices 1 changed 
         ;
 	
 \ TODO saving