From 6a4ff347da8cda7340cea1a783b25006904702b1 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sat, 10 Jun 2023 22:37:29 -0400
Subject: [PATCH] sb: fix blue/orange sprite to have pseudo transparency

---
 games/sb/TODO             | 32 +++++++++++++++++++-------------
 games/sb/hgr_sprite_big.s | 20 ++++++++++++++++++++
 2 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/games/sb/TODO b/games/sb/TODO
index ca0df978..534e85f6 100644
--- a/games/sb/TODO
+++ b/games/sb/TODO
@@ -1,5 +1,14 @@
-Title
-+ ?
+Strongbadzone:
++ Implement rest of audio
++ Ball movement logic.  Is actually just 2D
+  -> Collision detect with head.  Decrement count, play sound
+  -> Collision detect with player
++ Do the color mask (different blacks)
++ Animate side walls
+  -> This is going to involve fancy memory management
++ Faster hgr copy?
++ Optimize sprite size
++ Allow lowercase keyboard (see duck code)
 
 Duck:
 + Implement throwing
@@ -8,21 +17,18 @@ Duck:
 + Implement easter eggs
 + Exit back to main title
 
-Rat:
-+ ?
 
-Strongbadzone:
-+ Get audio
-+ Ball movement logic.  Is actually just 2D
-+ Check bounds on person
-+ Do the color mask (different blacks)
-+ Animate side walls
-+ Faster hgr copy?
-+ Optimize sprite size
-+ Allow lowercase keyboard (see duck code)
 
 Cliff:
 + Everything
 
 Jump
 + Everything
+
+Rat:
++ Done?
+
+Title
++ Done?
+
+
diff --git a/games/sb/hgr_sprite_big.s b/games/sb/hgr_sprite_big.s
index 9a8d0d2f..e25645eb 100644
--- a/games/sb/hgr_sprite_big.s
+++ b/games/sb/hgr_sprite_big.s
@@ -3,6 +3,9 @@
 	;===========================================
 	; can handle sprites bigger than a 256 byte page
 
+	; Note this is optimized for blue/orange sprites
+	;   it treats black0 as transparent
+
 	; SPRITE in INL/INH
 	; Location at SPRITE_X SPRITE_Y
 
@@ -66,8 +69,10 @@ big_sprite_inner_loop:
 
 big_sprite_smc1:
         lda	$f000,X			; load sprite data
+	beq	big_sprite_transparent
 	sta	(GBASL),Y		; store to screen
 
+big_sprite_transparent:
 	inx				; increment sprite offset
 
 	; if > 1 page
@@ -146,7 +151,20 @@ osprite_inner_loop:
 osprite_smc1:
         lda	$f000,X			; load sprite data
 
+	bne	osprite_not_transparent
+
+	; we can't just skip if 0 because we might shift a bit in
+	; from previous byte
+
+	plp
+	bcs	osprite_oops
+	clc
+	php
+	bcc	osprite_transparent_done
+
+osprite_not_transparent:
 	plp				; restore carry from last
+osprite_oops:
 	rol				; rotate in carry
 	asl				; one more time, bit6 in carry
 	php				; save on stack
@@ -155,6 +173,8 @@ osprite_smc1:
 
 	sta	(GBASL),Y		; store to screen
 
+
+osprite_transparent_done:
 	inx				; increment sprite offset
 
 	; if > 1 page