Skip player update if the background is scrolling

inc/util.inc

@@ -5,3 +5,12 @@ MACRO STORE16
     inc hl
     ld [hl], LOW(\1)
 ENDM
+
+; Stores an 8-bit value into memory
+; \1 Write address
+; \2 8-bit value
+MACRO SET8
+    ld h, HIGH(\1)
+    ld l, LOW(\1)
+    ld [hl], \2
+ENDM

src/bg.s

@@ -1,4 +1,6 @@
 INCLUDE "hardware.inc"
+INCLUDE "util.inc"
+
 INCLUDE "png/map/intro.inc"
 
 SECTION "BG Data", WRAM0
@@ -7,6 +9,8 @@ BG_COLLISION_DATA:: dw
 BG_MAP_WIDTH:: db
 BG_MAP_HEIGHT:: db
 
+BG_SCROLLING:: db
+
 SECTION "BG Code", ROM0
 
 MACRO update_map_info
@@ -24,6 +28,8 @@ MACRO update_map_info
 ENDM
 
 BG_Init::
+    SET8 BG_SCROLLING, 0
+
     ; copy map
     ld e, intro_HEIGHT
     ld bc, _SCRN0
@@ -58,3 +64,6 @@ BG_Init::
     update_map_info intro_COLLISION, intro_WIDTH, intro_HEIGHT
 
     ret
+
+BG_Update::
+    ret

src/main.s

@@ -53,6 +53,7 @@ start:
 
     call Keys_Update
     call Player_Update
+    call BG_Update
 
     ; wait for vblank
     halt

src/player.s

@@ -60,10 +60,15 @@ Player_Init::
     ret
 
 Player_Update::
-    ld hl, keys
-    ld b, [hl]
+    ; suspend player state while map is scrolling
+    ld hl, BG_SCROLLING
+    ld a, [hl]
+    or a
+    ret nz
 
     ; check for jump
+    ld hl, keys
+    ld b, [hl]
     ld a, b
     and BTN_UP
     jr z, .jump_update_check