diff --git a/src/lars/lites.79 b/src/lars/lites.80
similarity index 67%
rename from src/lars/lites.79
rename to src/lars/lites.80
index fe902e00..8f5326f6 100644
--- a/src/lars/lites.79
+++ b/src/lars/lites.80
@@ -3,20 +3,24 @@
 ;Default is to build for both TS and NTS.
 IFNDEF TS,TS==1
 IFNDEF NTS,NTS==1
+IFE TS+NTS,.ERR Must choose at least one of TS or NTS.
 
 A=1
 B=2
+C=3
 T=10
 TT=11
-Q=16
+PC=16
 P=17
 
+COCALL=JSP PC,(PC)			;Coroutine call.
+
 APR==0
 PI==4
 
-TICKS=20*60.				;20 seconds.
+TICKS=20.*60.				;Each pattern displayed for 20 seconds.
 PDLLEN==20
-
+
 GO:	MOVE P,[-PDLLEN,,PDL-1]
 IFN TS,[
 	;Timesharing code starts here.  If not present, fall through to 
@@ -32,16 +36,14 @@ IFN TS,[
 	.REALT A,			;Clock interrupt every 1/60 seconds.
 	.SUSET [.SMASK,,[%PIRLT]]
 	JFCL
-	 .HANG
+	 .HANG				;Now entirely interrupt driven.
 
 TSINT:	0
 	0
-	PUSH P,A
-	SKIPL A,TSINT
-	 TLNN A,(%PIRLT)		;Is this the clock interrupt?
-	  .DISMIS TSINT+1
-	POP P,A
-	PUSHJ P,LITES
+	SKIPL T,TSINT
+	 TLNN T,(%PIRLT)		;Is this the clock interrupt?
+	  .DISMIS TSINT+1		;No, dismiss immediately.
+	PUSHJ P,LITES			;Yes, do our thing.
 	.DISMIS TSINT+1
 
 ZZ==.
@@ -49,19 +51,19 @@ LOC 42
 	TSINT
 LOC ZZ
 ]
-
+
 IFN NTS,[
 	;Non-timesharing code starts here.  If the TS code is executed
 	;first, the UUO handler will be called and jump here.
 NTS1:	CONO APR,3002			;APR interrupt at channel 2, enable clock.
 	CONO PI,12240			;Enable interrupt.
-	JRST .
+	JRST .				;Now entirely interrupt driven.
 
 APRBRK:	0
 	CONSO APR,1000			;Is this the clock interrupt?
-	 JRST 12,@APRBRK
-	PUSHJ P,LITES
-	CONO APR,1002
+	 JRST 12,@APRBRK		;No, dismiss immediately.
+	PUSHJ P,LITES			;Yes, do our thing.
+	CONO APR,1002			;Clear clock interrupt.
 	JRST 12,@APRBRK
 
 ZZ==.
@@ -73,52 +75,47 @@ LOC 44
 	JSR APRBRK
 LOC ZZ
 ]
+
+LITES:	AOSN TICK
+	 PUSHJ P,NEW			;Pattern ran out of ticks, get new one.
+	COCALL	
+	DATAO PI,A			;Display A on memory indicators.
+	POPJ P,
 
-LITES:	PUSH P,A
-	SKIPE TICK
-	 JRST LITES0
-	MOVE A,[TICKS]			;Pattern ran out of ticks, get new one.
+NEW:	MOVNI A,TICKS			;Start a new pattern.
 	MOVEM A,TICK
 	MOVE A,PATRN
 	CAIN A,PATRNE
 	 MOVEI A,PATRNS			;Reached end of list.
 	MOVEM A,PATRN
-	MOVE A,@PATRN
+	MOVE PC,@PATRN
 	AOS PATRN
-	MOVEM A,PC'
-LITES0:	MOVE Q,PC
-	POP P,A
-	JSP Q,(Q)			;Coroutine call.
-	MOVEM Q,PC
-	DATAO PI,A			;Display A on memory indicators.
-	SOS TICK
 	POPJ P,
-
-
+
 COUNTER:				;Simple counter pattern.
 	SETZ A,
-	JSP Q,(Q)
+COUNT0:	COCALL
 	AOS A
-	JRST .-2
+	JRST COUNT0
 
 ROT777:	MOVEI A,777			;Rotating pattern.
-	JSP Q,(Q)
+	COCALL
 	ROT A,1
 	JRST .-2
 
 .INSRT XOROSH
 
 RANDOM:	PUSHJ P,XOROSHIRO"XOROSHIRO	;Random generator.
-	JSP Q,(Q)
+	COCALL
 	JRST RANDOM
 
 SAIL:	SETZ A,				;SAIL null job.
 SAIL0:	ROT A,-1
 	TLNN A,200000
 	TLC A,400000
-	JSP Q,(Q) ? JSP Q,(Q) ? JSP Q,(Q)
+	COCALL ? COCALL ? COCALL
 	JRST SAIL0
-
+
 PATRNS:	COUNTER
 	ROT777
 	RANDOM
@@ -126,7 +123,7 @@ PATRNS:	COUNTER
 PATRNE:
 
 PATRN:	PATRNE
-TICK:	0
+TICK:	-1
 PDL:	BLOCK PDLLEN
 
 END GO