Identify JOYP_SGB_MLT_REQ constant

Author: Rangi42

constants/misc_constants.asm

@@ -57,3 +57,6 @@ DEF HOF_MASTER_COUNT EQU 200
 
 ; card flip
 DEF CARDFLIP_DECK_SIZE EQU 4 * 6
+
+; SGB command MLT_REQ can be used to detect SGB hardware
+DEF JOYP_SGB_MLT_REQ EQU %00000011

engine/gfx/color.asm

@@ -908,8 +908,8 @@ PushSGBBorderPalsAndWait:
 	call _PushSGBPals
 	call SGBDelayCycles
 	ldh a, [rJOYP]
-	and $3
-	cp $3
+	and JOYP_SGB_MLT_REQ
+	cp JOYP_SGB_MLT_REQ
 	jr nz, .carry
 	ld a, JOYP_SGB_ZERO
 	ldh [rJOYP], a
@@ -936,8 +936,8 @@ endr
 	call SGBDelayCycles
 	call SGBDelayCycles
 	ldh a, [rJOYP]
-	and $3
-	cp $3
+	and JOYP_SGB_MLT_REQ
+	cp JOYP_SGB_MLT_REQ
 	jr nz, .carry
 	call .FinalPush
 	and a