From 8824bb5c249b645f5d9aa0d2747535180a8f9753 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Mon, 2 Feb 2026 17:36:42 +0100
Subject: [PATCH] math: Added carry flag for m16

---
 src/attributes.s |  7 +++++++
 src/defs.s       |  4 ++++
 src/math.s       | 19 +++++++++++++++++++
 src/wram.s       |  2 ++
 4 files changed, 32 insertions(+)

diff --git a/src/attributes.s b/src/attributes.s
index f70e9d3..ed325fb 100644
--- a/src/attributes.s
+++ b/src/attributes.s
@@ -152,6 +152,13 @@ act_attr_take_weapon_damage:
 
 	pop de
 	call act_attr_write_hp
+	
+	BREAK
+	; if m16_flags carry is set 
+	; -> die
+	ld a, [m16_flags]
+	and a, M16_CARRY
+	ret z ; no carry?
 
 	call act_die
 	ret
diff --git a/src/defs.s b/src/defs.s
index 9e8e307..7584686 100644
--- a/src/defs.s
+++ b/src/defs.s
@@ -316,3 +316,7 @@
 .de os_data, (OS_WIDTH * OS_HEIGHT)
 .de os_size, 0
 
+
+	; 16 bit math flags
+.se 1
+.de M16_CARRY, 1
diff --git a/src/math.s b/src/math.s
index c83aed8..caec838 100644
--- a/src/math.s
+++ b/src/math.s
@@ -53,7 +53,11 @@
 	;		m16_a/m16_b
 	;	returns:
 	;		m16_a: m16_a + m16_b
+	;		m16_flags
 m16_add:
+	xor a, a
+	ld [m16_flags], a
+
 	ld a, [m16_b]
 	ld b, a
 	ld a, [m16_a]
@@ -69,6 +73,11 @@ m16_add:
 	; high + carry stored
 	adc a, b
 	ld [m16_a+1], a
+	ret nc ; no carry? good to exit
+
+	; when carry is set -> set flag
+	ld a, M16_CARRY
+	ld [m16_flags], a
 
 	ret
 
@@ -77,7 +86,11 @@ m16_add:
 	;		m16_a/m16_b
 	;	returns:
 	;		m16_a: m16_a - m16_b
+	;		m16_flags
 m16_sub:
+	xor a, a
+	ld [m16_flags], a
+
 	ld a, [m16_b]
 	ld b, a
 	ld a, [m16_a]
@@ -93,4 +106,10 @@ m16_sub:
 	; high + carry stored
 	sbc a, b
 	ld [m16_a+1], a
+	ret nc
+
+	; when carry is set -> set flag
+	ld a, M16_CARRY
+	ld [m16_flags], a
+
 	ret
diff --git a/src/wram.s b/src/wram.s
index b30b9a1..9099c76 100644
--- a/src/wram.s
+++ b/src/wram.s
@@ -146,6 +146,8 @@ col_x: .adv 1
 	; store in LE
 m16_a: .adv 2
 m16_b: .adv 2
+	; flags for 16 bit math
+m16_flags: .adv 1
 
 ticks: .adv 1
 
-- 
2.30.2