5 files changed, 121 insertions, 32 deletions
diff --git a/src/engine/bank01.asm b/src/engine/bank01.asm
index 0b288b8..85bf0c8 100644
--- a/src/engine/bank01.asm
+++ b/src/engine/bank01.asm
@@ -7,9 +7,9 @@ GameLoop: ; 4000 (1:4000)
 	call EnableInt_VBlank
 	call EnableInt_Timer
 	call EnableSRAM
-	ld a, [sa006]
+	ld a, [s0a006]
 	ld [wTextSpeed], a
-	ld a, [sa009]
+	ld a, [s0a009]
 	ld [wccf2], a
 	call DisableSRAM
 	ld a, 1
@@ -30,7 +30,7 @@ GameLoop: ; 4000 (1:4000)
 ; erase sram
 	call EnableSRAM
 	xor a
-	ld [sa000], a
+	ld [s0a000], a
 	call DisableSRAM
 .reset_game
 	jp Reset
@@ -360,7 +360,7 @@ PrintDuelMenu: ; 4295 (1:4295)
 	ld hl, DuelMenuData
 	call PlaceTextItems
 .asm_429e
-	call $669d
+	call SaveDuelData
 	ld a, [wDuelFinished]
 	or a
 	ret nz
@@ -3847,7 +3847,91 @@ Func_6673: ; 6673 (1:6673)
 	ret
 ; 0x669d
 
-	INCROM $669d, $6785
+; save data of the current duel to sCurrentDuelData
+; byte 0 is $01, bytes 1 and 2 are the checksum, byte 3 is [wDuelType]
+; next $33a bytes come from DuelDataToSave
+SaveDuelData: ; 669d (1:669d)
+	farcall CommentedOut_1a6cc
+	ld de, sCurrentDuelData
+;	fallthrough
+
+; save data of the current duel to de (in SRAM)
+; byte 0 is $01, bytes 1 and 2 are the checksum, byte 3 is [wDuelType]
+; next $33a bytes come from DuelDataToSave
+SaveDuelDataToDE: ; 66a4 (1:66a4)
+	call EnableSRAM
+	push de
+	inc de
+	inc de
+	inc de
+	inc de
+	ld hl, DuelDataToSave
+	push de
+.save_duel_data_loop
+	; start copying data to de = sCurrentDuelData + 4
+	ld c, [hl]
+	inc hl
+	ld b, [hl]
+	inc hl
+	ld a, c
+	or b
+	jr z, .asm_66c7
+	push hl
+	push bc
+	ld c, [hl]
+	inc hl
+	ld b, [hl]
+	inc hl
+	pop hl
+	call CopyDataHLtoDE
+	pop hl
+	inc hl
+	inc hl
+	jr .save_duel_data_loop
+.asm_66c7
+	pop hl
+	; hl = sCurrentDuelData + 4
+	lb de, $23, $45
+	ld bc, $334 ; misses last 6 bytes to calculate checksum
+.checksum_loop
+	ld a, e
+	sub [hl]
+	ld e, a
+	ld a, [hli]
+	xor d
+	ld d, a
+	dec bc
+	ld a, c
+	or b
+	jr nz, .checksum_loop
+	pop hl
+	ld a, $01
+	ld [hli], a ; sCurrentDuelData
+	ld [hl], e ; sCurrentDuelData + 1
+	inc hl
+	ld [hl], d ; sCurrentDuelData + 2
+	inc hl
+	ld a, [wDuelType]
+	ld [hl], a ; sCurrentDuelData + 3
+	call DisableSRAM
+	ret
+; 0x66e9
+
+	INCROM $66e9, $6729
+
+DuelDataToSave: ; 6729 (1:6729)
+;	dw address, number_of_bytes_to_copy
+	dw wPlayerDuelVariables, wOpponentDuelVariables - wPlayerDuelVariables
+	dw wOpponentDuelVariables, wPlayerDeck - wOpponentDuelVariables
+	dw wPlayerDeck, wc500 + $10 - wPlayerDeck
+	dw wcc05, wDuelTheme + $1 - wcc05
+	dw hWhoseTurn, $1
+	dw wRNG1, wRNGCounter + $1 - wRNG1
+	dw wcda5, $0010
+	dw $0000
+; 0x6747
+
+	INCROM $6747, $6785
 
 Func_6785: ; 6785 (1:6785)
 	call EnableSRAM
diff --git a/src/engine/bank03.asm b/src/engine/bank03.asm
index 218be30..7ad9a33 100644
--- a/src/engine/bank03.asm
+++ b/src/engine/bank03.asm
@@ -267,9 +267,9 @@ Func_c1f8: ; c1f8 (3:41f8)
 	ld [wd112], a
 	ld [wd3b8], a
 	call EnableSRAM
-	ld a, [sa007]
+	ld a, [s0a007]
 	ld [wd421], a
-	ld a, [sa006]
+	ld a, [s0a006]
 	ld [wTextSpeed], a
 	call DisableSRAM
 	farcall Func_10756
diff --git a/src/engine/bank04.asm b/src/engine/bank04.asm
index 55657db..da12df8 100644
--- a/src/engine/bank04.asm
+++ b/src/engine/bank04.asm
@@ -1113,9 +1113,9 @@ MainMenu_NewGame: ; 12704 (4:6704)
 	call Func_128a9
 	farcall Func_1996e
 	call EnableSRAM
-	ld a, [sa007]
+	ld a, [s0a007]
 	ld [wd421], a
-	ld a, [sa006]
+	ld a, [s0a006]
 	ld [wTextSpeed], a
 	call DisableSRAM
 	ld a, MUSIC_STOP
diff --git a/src/engine/bank06.asm b/src/engine/bank06.asm
index fc5e5c4..bc38b82 100644
--- a/src/engine/bank06.asm
+++ b/src/engine/bank06.asm
@@ -167,13 +167,13 @@ Func_1996e: ; 1996e (6:596e)
 	or b
 	jr nz, .asm_1997b
 	ld a, $5
-	ld hl, sa350
+	ld hl, s0a350
 	call Func_199e0
 	ld a, $7
-	ld hl, sa3a4
+	ld hl, s0a3a4
 	call Func_199e0
 	ld a, $9
-	ld hl, sa3f8
+	ld hl, s0a3f8
 	call Func_199e0
 	call EnableSRAM
 	ld hl, sCardCollection
@@ -196,16 +196,16 @@ Func_1996e: ; 1996e (6:596e)
 	dec c
 	jr nz, .asm_199b2
 	ld a, $2
-	ld [sa003], a
+	ld [s0a003], a
 	ld a, $2
-	ld [sa006], a
+	ld [s0a006], a
 	ld [wTextSpeed], a
 	xor a
-	ld [sa007], a
-	ld [sa009], a
-	ld [sa004], a
-	ld [sa005], a
-	ld [sa00a], a
+	ld [s0a007], a
+	ld [s0a009], a
+	ld [s0a004], a
+	ld [s0a005], a
+	ld [s0a00a], a
 	farcall Func_8cf9
 	call DisableSRAM
 	ret
diff --git a/src/engine/home.asm b/src/engine/home.asm
index 79bdf8c..05c6d21 100644
--- a/src/engine/home.asm
+++ b/src/engine/home.asm
@@ -1394,7 +1394,7 @@ CGBSpeedSwitch: ; 07f1 (0:07f1)
 	ret
 
 ; validate the saved data in SRAM
-; it must contain with the sequence $04, $21, $05 at sa000
+; it must contain with the sequence $04, $21, $05 at s0a000
 ValidateSRAM: ; 080b (0:080b)
 	xor a
 	call BankswitchSRAM
@@ -1417,7 +1417,7 @@ ValidateSRAM: ; 080b (0:080b)
 	call DisableSRAM
 	ret
 .check_sequence
-	ld hl, sa000
+	ld hl, s0a000
 	ld a, [hli]
 	cp $04
 	jr nz, .restart_sram
@@ -1435,7 +1435,7 @@ ValidateSRAM: ; 080b (0:080b)
 	call DisableSRAM
 	ret
 
-; zero all SRAM banks and set sa000 to $04, $21, $05
+; zero all SRAM banks and set s0a000 to $04, $21, $05
 RestartSRAM: ; 084d (0:084d)
 	ld a, 3
 .clear_loop
@@ -1443,7 +1443,7 @@ RestartSRAM: ; 084d (0:084d)
 	dec a
 	cp -1
 	jr nz, .clear_loop
-	ld hl, sa000
+	ld hl, s0a000
 	ld [hl], $04
 	inc hl
 	ld [hl], $21
@@ -2584,7 +2584,7 @@ SerialRecvByte: ; 0e39 (0:0e39)
 	or a
 	ret
 
-; exchange c bytes. send bytes at hl and store received bytes at de
+; exchange c bytes. send bytes at hl and store received bytes in de
 SerialExchangeBytes: ; 0e63 (0:0e63)
 	ld b, c
 .asm_e64
@@ -2815,7 +2815,7 @@ ExchangeRNG: ; 0f58 (0:0f58)
 ; sets hAIActionTableIndex to an AI action specified in register a.
 ; send 10 bytes of data to the other game from hAIActionTableIndex, hTempCardIndex_ff9f,
 ; hTemp_ffa0, and hTempPlayAreaLocationOffset_ffa1, and hTempRetreatCostCards.
-; finally exchange RNG data
+; finally exchange RNG data.
 SetAIAction_SerialSendDuelData: ; 0f7f (0:0f7f)
 	push hl
 	push bc
@@ -2835,7 +2835,8 @@ SetAIAction_SerialSendDuelData: ; 0f7f (0:0f7f)
 ; 0xf9b
 
 ; receive 10 bytes of data from wSerialRecvBuf and store them into hAIActionTableIndex,
-; hTempCardIndex_ff9f, hTemp_ffa0, and hTempPlayAreaLocationOffset_ffa1, and hTempRetreatCostCards
+; hTempCardIndex_ff9f, hTemp_ffa0, and hTempPlayAreaLocationOffset_ffa1,
+; and hTempRetreatCostCards. also exchange RNG data.
 SerialRecvDuelData: ; 0f9b (0:0f9b)
 	push hl
 	push bc
@@ -2932,20 +2933,23 @@ SerialRecv8Bytes: ; 0fe9 (0:0fe9)
 ; 0x100b
 
 ; save duel state to SRAM
-; called between each two-player turn, just after player draws card
+; called between each two-player turn, just after player draws card (bank 1 loaded)
 SaveDuelStateToSRAM: ; 100b (0:100b)
 	ld a, $2
 	call BankswitchSRAM
-	call $669d
+	; save duel data to sCurrentDuelData
+	call SaveDuelData
 	xor a
 	call BankswitchSRAM
 	call EnableSRAM
-	ld hl, sa008
+	ld hl, s0a008
 	ld a, [hl]
 	inc [hl]
 	call DisableSRAM
+	; select hl = SRAM3:(a000 + $400 * [s0a008] & $3)
+	; save wDuelTurns, non-turn holder's arena card ID, turn holder's arena card ID
 	and $3
-	add $28
+	add HIGH($a000) / 4
 	ld l, $0
 	ld h, a
 	add hl, hl
@@ -2974,13 +2978,14 @@ SaveDuelStateToSRAM: ; 100b (0:100b)
 	ld [hli], a
 	ld a, [wTempTurnDuelistCardID]
 	ld [hli], a
+	; save duel data to SRAM3:(a000 + $400 * [s0a008] & $3) + $0010
 	pop hl
 	ld de, $0010
 	add hl, de
 	ld e, l
 	ld d, h
 	call DisableSRAM
-	bank1call $66a4
+	bank1call SaveDuelDataToDE
 	xor a
 	call BankswitchSRAM
 	ret
@@ -10660,7 +10665,7 @@ Func_3917: ; 3917 (0:3917)
 	ld a, $22
 	farcall CheckIfEventFlagSet
 	call EnableSRAM
-	ld [sa00a], a
+	ld [s0a00a], a
 	call DisableSRAM
 	ret