diff --git a/src/constants/gfx_constants.asm b/src/constants/gfx_constants.asm
index 0d98459..200f53d 100644
--- a/src/constants/gfx_constants.asm
+++ b/src/constants/gfx_constants.asm
@@ -4,7 +4,7 @@ DEF palettes EQUS "* PAL_SIZE"
 DEF NUM_BACKGROUND_PALETTES EQU 8
 DEF NUM_OBJECT_PALETTES     EQU 8
 
-DEF PALRGB_WHITE EQU (31 << B_COLOR_BLUE) | (31 << B_COLOR_GREEN) | (31 << B_COLOR_RED)
+DEF PALRGB_WHITE EQU (COLOR_CH_MAX << B_COLOR_BLUE) | (COLOR_CH_MAX << B_COLOR_GREEN) | (COLOR_CH_MAX << B_COLOR_RED)
 
 ; tile size
 DEF tiles EQUS "* TILE_SIZE"
diff --git a/src/constants/hardware.inc b/src/constants/hardware.inc
index e77034f..e1e3b2c 100644
--- a/src/constants/hardware.inc
+++ b/src/constants/hardware.inc
@@ -22,7 +22,7 @@ endc
 ; Define the include guard and the current hardware.inc version
 ; (do this after the RGBDS version check since the `def` syntax depends on it)
 def HARDWARE_INC equ 1
-def HARDWARE_INC_VERSION equs "5.2.0"
+def HARDWARE_INC_VERSION equs "5.3.0"
 
 ; Usage: rev_Check_hardware_inc <min_ver>
 ; Examples:
@@ -76,6 +76,14 @@ def B_JOYP_RIGHT  equ 0 ; 0 = Right is pressed  (if reading Control Pad) [ro]
     def JOYP_LEFT   equ 1 << B_JOYP_LEFT
     def JOYP_RIGHT  equ 1 << B_JOYP_RIGHT
 
+; SGB command packet transfer uses for JOYP bits
+def B_JOYP_SGB_ONE  equ 5 ; 0 = sending 1 bit
+def B_JOYP_SGB_ZERO equ 4 ; 0 = sending 0 bit
+    def JOYP_SGB_START  equ %00_00_0000 ; start SGB packet transfer
+    def JOYP_SGB_ONE    equ %00_01_0000 ; send 1 bit
+    def JOYP_SGB_ZERO   equ %00_10_0000 ; send 0 bit
+    def JOYP_SGB_FINISH equ %00_11_0000 ; finish SGB packet transfer
+
 ; Combined input byte, with Control Pad in high nybble (conventional order)
 def B_PAD_DOWN   equ 7
 def B_PAD_UP     equ 6
@@ -96,7 +104,6 @@ def B_PAD_A      equ 0
     def PAD_B        equ 1 << B_PAD_B
     def PAD_A        equ 1 << B_PAD_A
 
-
 ; Combined input byte, with Control Pad in low nybble (swapped order)
 def B_PAD_SWAP_START  equ 7
 def B_PAD_SWAP_SELECT equ 6
@@ -222,7 +229,7 @@ def AUD1ENV_PACE equ %00000_111 ; how long between envelope iterations
                                 ; (in 64 Hz ticks, ~15.6 ms apart) [r/w]
 
 ; -- AUD1LOW / NR13 ($FF13) ---------------------------------------------------
-; Audio channel 1 period (low 8 bits) [r/w]
+; Audio channel 1 period (low 8 bits) [wo]
 def rAUD1LOW equ $FF13
 
 ; -- AUD1HIGH / NR14 ($FF14) --------------------------------------------------
@@ -266,7 +273,7 @@ def AUD2ENV_PACE equ %00000_111 ; how long between envelope iterations
                                 ; (in 64 Hz ticks, ~15.6 ms apart) [r/w]
 
 ; -- AUD2LOW / NR23 ($FF18) ---------------------------------------------------
-; Audio channel 2 period (low 8 bits) [r/w]
+; Audio channel 2 period (low 8 bits) [wo]
 def rAUD2LOW equ $FF18
 
 ; -- AUD2HIGH / NR24 ($FF19) --------------------------------------------------
@@ -304,7 +311,7 @@ def AUD3LEVEL_VOLUME equ %0_11_00000 ; volume level [r/w]
     def AUD3LEVEL_25   equ %0_11_00000 ; 25%
 
 ; -- AUD3LOW / NR33 ($FF1D) ---------------------------------------------------
-; Audio channel 3 period (low 8 bits) [r/w]
+; Audio channel 3 period (low 8 bits) [wo]
 def rAUD3LOW equ $FF1D
 
 ; -- AUD3HIGH / NR34 ($FF1E) --------------------------------------------------
@@ -927,15 +934,18 @@ def TILE_HEIGHT equ  8 ; height of tile in pixels
 def TILE_SIZE   equ 16 ; size of tile in bytes (2 bits/pixel)
 
 def COLOR_SIZE equ 2 ; size of color in bytes (little-endian BGR555)
-    def B_COLOR_RED   equ  0 ; bits 4-0
-    def B_COLOR_GREEN equ  5 ; bits 9-5
-    def B_COLOR_BLUE  equ 10 ; bits 14-10
+def PAL_COLORS equ 4 ; colors per palette
+def PAL_SIZE   equ COLOR_SIZE * PAL_COLORS ; size of palette in bytes
+
+def COLOR_CH_WIDTH equ 5 ; bits per RGB color channel
+def COLOR_CH_MAX   equ (1 << COLOR_CH_WIDTH) - 1
+    def B_COLOR_RED   equ COLOR_CH_WIDTH * 0 ; bits 4-0
+    def B_COLOR_GREEN equ COLOR_CH_WIDTH * 1 ; bits 9-5
+    def B_COLOR_BLUE  equ COLOR_CH_WIDTH * 2 ; bits 14-10
         def COLOR_RED        equ %000_11111  ; for the low byte
         def COLOR_GREEN_LOW  equ %111_00000  ; for the low byte
         def COLOR_GREEN_HIGH equ %0_00000_11 ; for the high byte
         def COLOR_BLUE       equ %0_11111_00 ; for the high byte
-def PAL_COLORS equ 4 ; colors per palette
-def PAL_SIZE   equ COLOR_SIZE * PAL_COLORS ; size of palette in bytes
 
 ; (DMG only) grayscale shade indexes for BGP, OBP0, and OBP1
 def SHADE_WHITE equ %00
@@ -1032,6 +1042,22 @@ def B_BOOTUP_B_AGB equ 0
     def BOOTUP_B_CGB equ 0 << B_BOOTUP_B_AGB
     def BOOTUP_B_AGB equ 1 << B_BOOTUP_B_AGB
 
+; Register C = CPU qualifier
+def BOOTUP_C_DMG equ $13
+def BOOTUP_C_SGB equ $14
+def BOOTUP_C_CGB equ $00 ; CGB or AGB
+
+; Register D = color qualifier
+def BOOTUP_D_MONO  equ $00 ; DMG, MGB, SGB, or CGB or AGB in DMG mode
+def BOOTUP_D_COLOR equ $FF ; CGB or AGB
+
+; Register E = CPU qualifier (distinguishes DMG variants)
+def BOOTUP_E_DMG0        equ $C1
+def BOOTUP_E_DMG         equ $C8
+def BOOTUP_E_SGB         equ $00
+def BOOTUP_E_CGB_DMGMODE equ $08 ; CGB or AGB in DMG mode
+def BOOTUP_E_CGB         equ $56 ; CGB or AGB
+
 
 ;******************************************************************************
 ; Aliases
diff --git a/src/constants/misc_constants.asm b/src/constants/misc_constants.asm
index 748dd90..071cdec 100644
--- a/src/constants/misc_constants.asm
+++ b/src/constants/misc_constants.asm
@@ -5,7 +5,7 @@ DEF CONSOLE_CGB EQU $02
 
 ; wReentrancyFlag bits
 DEF IN_VBLANK EQU 0
-DEF IN_TIMER EQU 1
+DEF IN_TIMER  EQU 1
 
 ; wFlushPaletteFlags constants
 DEF FLUSH_ONE_PAL    EQU %10000000
@@ -40,17 +40,13 @@ DEF CARDPOP_NAME_LIST_SIZE EQUS "CARDPOP_NAME_LIST_MAX_ELEMS * NAME_BUFFER_LENGT
 
 DEF NUM_CHALLENGE_MACHINE_OPPONENTS EQU 5
 
-; rJOYP constants to read IR signals or SNES input
-DEF P15              EQU %00100000
-DEF P14              EQU %00010000
-DEF P13              EQU %00001000
-DEF P12              EQU %00000100
-DEF P11              EQU %00000010
-DEF P10              EQU %00000001
-DEF SNES_JOYPAD1     EQU $3 ; lower two bits
-DEF SNES_JOYPAD2     EQU $2 ; lower two bits
-DEF SNES_JOYPAD3     EQU $1 ; lower two bits
-DEF SNES_JOYPAD4     EQU $0 ; lower two bits
+; rJOYP constants to read SNES input
+DEF JOYP_SGB_MLT_REQ EQU %00000011
+
+; rJOYP constants to read IR signals
+DEF P14 EQU %00010000
+DEF P11 EQU %00000010
+DEF P10 EQU %00000001
 
 ; commands transmitted through IR to be
 ; executed by the other device
diff --git a/src/engine/link/ir_core.asm b/src/engine/link/ir_core.asm
index 8ee6f67..fc49bbc 100644
--- a/src/engine/link/ir_core.asm
+++ b/src/engine/link/ir_core.asm
@@ -145,7 +145,7 @@ Func_19705:
 	ld hl, rRP
 .loop
 	ldh a, [rJOYP]
-	bit 1, a
+	bit 1, a ; P11
 	jr z, ReturnZFlagUnsetAndCarryFlagSet
 	ld a, $aa ; request
 	call TransmitByteThroughIR
@@ -162,7 +162,7 @@ Func_1971e:
 	ld hl, rRP
 .asm_19721
 	ldh a, [rJOYP]
-	bit 1, a
+	bit 1, a ; P11
 	jr z, ReturnZFlagUnsetAndCarryFlagSet
 	call ReceiveByteThroughIR_ZeroIfUnsuccessful
 	cp $aa ; request
diff --git a/src/home/double_speed.asm b/src/home/double_speed.asm
index 9db6e34..f18f1ad 100644
--- a/src/home/double_speed.asm
+++ b/src/home/double_speed.asm
@@ -26,7 +26,7 @@ CGBSpeedSwitch::
 	xor a
 	ldh [rIF], a
 	ldh [rIE], a
-	ld a, $30
+	ld a, JOYP_GET_NONE
 	ldh [rJOYP], a
 	stop
 	call SetupTimer
diff --git a/src/home/input.asm b/src/home/input.asm
index 8b41ea9..4471fa2 100644
--- a/src/home/input.asm
+++ b/src/home/input.asm
@@ -48,7 +48,7 @@ Reset::
 SaveButtonsHeld::
 	ld a, c
 	ldh [hKeysHeld], a
-	ld a, JOYP_GET_CTRL_PAD | JOYP_GET_BUTTONS
+	ld a, JOYP_GET_NONE
 	ldh [rJOYP], a
 	ret
 
diff --git a/src/home/sgb.asm b/src/home/sgb.asm
index 62046be..adfe7e8 100644
--- a/src/home/sgb.asm
+++ b/src/home/sgb.asm
@@ -121,32 +121,32 @@ SendSGB::
 	ld c, LOW(rJOYP)
 .send_packets_loop
 	push bc
-	ld a, $0
+	ld a, JOYP_SGB_START
 	ld [$ff00+c], a
-	ld a, P15 | P14
+	ld a, JOYP_SGB_FINISH
 	ld [$ff00+c], a
 	ld b, SGB_PACKET_SIZE
 .send_packet_loop
-	ld e, $8
+	ld e, 8
 	ld a, [hli]
 	ld d, a
 .read_byte_loop
 	bit 0, d
-	ld a, P14 ; '1' bit
+	ld a, JOYP_SGB_ONE
 	jr nz, .transfer_bit
-	ld a, P15 ; '0' bit
+	ld a, JOYP_SGB_ZERO
 .transfer_bit
 	ld [$ff00+c], a
-	ld a, P15 | P14
+	ld a, JOYP_SGB_FINISH
 	ld [$ff00+c], a
 	rr d
 	dec e
 	jr nz, .read_byte_loop
 	dec b
 	jr nz, .send_packet_loop
-	ld a, P15 ; stop bit
+	ld a, JOYP_SGB_ZERO
 	ld [$ff00+c], a
-	ld a, P15 | P14
+	ld a, JOYP_SGB_FINISH
 	ld [$ff00+c], a
 	pop bc
 	dec b
@@ -163,16 +163,16 @@ DetectSGB::
 	ld hl, MltReq2Packet
 	call SendSGB
 	ldh a, [rJOYP]
-	and %11
-	cp SNES_JOYPAD1
+	and JOYP_SGB_MLT_REQ
+	cp JOYP_SGB_MLT_REQ
 	jr nz, .sgb
-	ld a, P15
+	ld a, JOYP_SGB_ZERO
 	ldh [rJOYP], a
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
-	ld a, P15 | P14
+	ld a, JOYP_SGB_FINISH
 	ldh [rJOYP], a
-	ld a, P14
+	ld a, JOYP_SGB_ONE
 	ldh [rJOYP], a
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
@@ -180,14 +180,14 @@ DetectSGB::
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
-	ld a, P15 | P14
+	ld a, JOYP_SGB_FINISH
 	ldh [rJOYP], a
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
 	ldh a, [rJOYP]
-	and %11
-	cp SNES_JOYPAD1
+	and JOYP_SGB_MLT_REQ
+	cp JOYP_SGB_MLT_REQ
 	jr nz, .sgb
 	ld hl, MltReq1Packet
 	call SendSGB