From f2c53974f3577be9e27be20206f81231ed089f0b Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sun, 13 Dec 2020 01:27:21 -0500
Subject: [PATCH] duke: closer to jumping properly

---
 duke/draw_duke.s | 39 +++++++++++++++++++++++++++++++++------
 duke/duke.s      |  1 +
 duke/zp.inc      |  2 +-
 3 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/duke/draw_duke.s b/duke/draw_duke.s
index bffa4966..81c1a37d 100644
--- a/duke/draw_duke.s
+++ b/duke/draw_duke.s
@@ -22,15 +22,28 @@ move_duke:
 
 duke_scroll_right:
 
+	clc
+	lda	DUKE_XL
+	adc	#$40
+	sta	DUKE_XL
+	bcc	skip_duke_scroll_right
+
 	inc	TILEMAP_X
 
 	jsr	copy_tilemap_subset
 
+skip_duke_scroll_right:
+
 	jmp	done_move_duke
 
 duke_walk_right:
+	lda	DUKE_XL
+	clc
+	adc	#$40
+	sta	DUKE_XL
+	bcc	dwr_noflo
 	inc	DUKE_X
-
+dwr_noflo:
 	jmp	done_move_duke
 
 move_left:
@@ -41,15 +54,29 @@ move_left:
 
 duke_scroll_left:
 
+	sec
+	lda	DUKE_XL
+	sbc	#$40
+	sta	DUKE_XL
+	bcs	skip_duke_scroll_left
+
 	dec	TILEMAP_X
 
 	jsr	copy_tilemap_subset
 
+skip_duke_scroll_left:
+
 	jmp	done_move_duke
 
 duke_walk_left:
-	dec	DUKE_X
 
+	lda	DUKE_XL
+	sec
+	sbc	#$40
+	sta	DUKE_XL
+	bcs	dwl_noflo
+	dec	DUKE_X
+dwl_noflo:
 	jmp	done_move_duke
 
 done_move_duke:
@@ -164,7 +191,7 @@ check_falling:
 
 	lda	DUKE_FOOT_OFFSET
 	clc
-	adc	#16			; underfoot is 16 more
+	adc	#16			; underfoot is on next row (+16)
 
 	tax
 	lda	TILEMAP,X
@@ -176,11 +203,11 @@ check_falling:
 	;=======================
 	; falling
 
-	; scroll but only if Y=18
+	; scroll but only if Y>=18
 
 	lda	DUKE_Y
 	cmp	#18
-	bne	scroll_fall
+	bcs	scroll_fall	; bge
 
 	inc	DUKE_Y
 	inc	DUKE_Y
@@ -201,7 +228,7 @@ feet_on_ground:
 	cmp	#18
 	bcs	done_check_falling	; bge
 
-	; too high up on screen, adjust down ad also adjust tilemap down
+	; too high up on screen, adjust down and also adjust tilemap down
 
 	inc	DUKE_Y
 	inc	DUKE_Y
diff --git a/duke/duke.s b/duke/duke.s
index c8874ebd..99ae9797 100644
--- a/duke/duke.s
+++ b/duke/duke.s
@@ -37,6 +37,7 @@ duke_start:
 	sta	DUKE_JUMPING
 	sta	LEVEL_OVER
 	sta	LASER_OUT
+	sta	DUKE_XL
 
 	lda	#4
 	sta	DRAW_PAGE
diff --git a/duke/zp.inc b/duke/zp.inc
index c0e9578b..7c614e10 100644
--- a/duke/zp.inc
+++ b/duke/zp.inc
@@ -78,8 +78,8 @@ PATTERN_H       = $7F
 ; when loading/storing from disk
 
 WHICH_LOAD		= $80		; which file to load
-;LOCATION		= $81		; location on the map
 
+DUKE_XL			= $81
 DUKE_X			= $82		; location of protagonist
 DUKE_Y			= $83
 DUKE_DIRECTION		= $84