From 5d790168f71631cf0bc124f5c41b27875b20b830 Mon Sep 17 00:00:00 2001
From: Peter Ferrie <peter.ferrie@gmail.com>
Date: Mon, 9 Mar 2020 08:06:53 -0700
Subject: [PATCH] simplify a bit

---
 src/ui.attract.dhgr.a | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/src/ui.attract.dhgr.a b/src/ui.attract.dhgr.a
index d2ba28969..6cef594d8 100644
--- a/src/ui.attract.dhgr.a
+++ b/src/ui.attract.dhgr.a
@@ -289,33 +289,25 @@ HGRByteToDHGRBytes
 ; out:   A = DHGR byte in mainmem
 ;        X = DHGR byte in auxmem
 ;        preserves Y
-;        clobbers zero page $00,$01,$02,$03
+;        clobbers zero page $00,$01,$02
 
          sty   $02
          ldy   #$02
-         sec
+--       stx   $01
+         ldx   #$04
+-        ror   $00                   ; duplicate previous bit
+         lsr                         ; fetch bit
          php
-         ldx   #$07
---       lsr
--        php
-         ror   $00
-         sec
-         dex
-         beq   +
+         ror   $00                   ; insert bit
          plp
-+        ror   $00
          dex
-         bpl   --
-         plp
-         ldx   $03
-         stx   $01
-         ldx   $00
-         stx   $03
-         ldx   #$06
-         dey
          bne   -
-         ror   $00
-         lda   $00
+         ldx   $00
+         dey
+         bne   --
+         txa
+         sec
+         ror   $01                   ; set bit 7 explicitly on auxmem value
          ldx   $01
          ldy   $02
          rts