From 9ab1595624270fef2c6dc5f91105d1f0013e5c2d Mon Sep 17 00:00:00 2001
From: Christian Johannesen <christian@johannesen.dk>
Date: Fri, 16 Oct 2026 12:30:59 +0200
Subject: [PATCH] Fix Neon Rift scroller and raster timing

---
 neon-rift/neon-rift.asm |  16 +++++++++++++++-
 neon-rift/neon-rift.prg | Bin 1981 -> 1993 bytes
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/neon-rift/neon-rift.asm b/neon-rift/neon-rift.asm
index 399c5da..a51a5c1 100644
--- a/neon-rift/neon-rift.asm
+++ b/neon-rift/neon-rift.asm
@@ -341,6 +341,16 @@ scroll_shift_loop:
     sty scroll_position
     lda scroll_message
 insert_scroll_char:
+    ; The message is stored as portable ASCII.  The VIC-II character screen
+    ; uses screen codes, where uppercase A-Z are 1-26 rather than 65-90.
+    ; Convert explicitly instead of relying on the assembler's active
+    ; conversion table.
+    cmp #65
+    bcc store_scroll_char
+    cmp #91
+    bcs store_scroll_char
+    and #$1f
+store_scroll_char:
     sta $07e7
     inc scroll_position
     lda palette
@@ -434,6 +444,9 @@ silence_sid:
     rts
 
 draw_raster_frame:
+    ; Keep the KERNAL IRQ from interrupting a color change halfway through a
+    ; raster line.  It is enabled again before returning to the main loop.
+    sei
     lda #45
     jsr wait_raster
     lda old_d016
@@ -469,6 +482,7 @@ raster_band_loop:
     and #$f8
     ora scroll_fine
     sta $d016
+    cli
     rts
 
 wait_raster:
@@ -626,7 +640,7 @@ bass_notes: !byte 0,0,0,0,3,3,3,3,5,5,5,5,3,3,1,1
 drum_steps: !byte 1,0,0,0,1,0,1,0,1,0,0,0,1,0,1,0
 
 scroll_message:
-!scr "   NEON RIFT   RASTER LIGHT MEETS EIGHT ORBITING SPRITES AND THREE VOICES OF SID   GREETINGS FROM C64.P20.DEV   "
+!text "   NEON RIFT   RASTER LIGHT MEETS EIGHT ORBITING SPRITES AND THREE VOICES OF SID   GREETINGS FROM C64.P20.DEV   "
 !byte 0
 
 star_positions_lo:
diff --git a/neon-rift/neon-rift.prg b/neon-rift/neon-rift.prg
index 1c2c77774813dacd266ea440d177666da8f46d66..872874ef221c5dd8a86cb30d77d92dfd69ce8bcc 100644
GIT binary patch
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