From e456eaed6d702c39796ed869c7c30b77027e9fe6 Mon Sep 17 00:00:00 2001
From: Sally Coolatta <tehrealsalt@gmail.com>
Date: Sun, 6 Nov 2022 14:58:31 -0500
Subject: [PATCH] SubtractNum also makes tripwire subtractive

---
 src/p_setup.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/p_setup.c b/src/p_setup.c
index 8e9eed1a5..efadfedd9 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -2631,6 +2631,7 @@ static void P_ProcessLinedefsAfterSidedefs(void)
 {
 	size_t i = numlines;
 	register line_t *ld = lines;
+	const boolean subtractTripwire = ((mapheaderinfo[gamemap - 1]->levelflags & LF_SUBTRACTNUM) == LF_SUBTRACTNUM);
 
 	for (; i--; ld++)
 	{
@@ -2645,7 +2646,7 @@ static void P_ProcessLinedefsAfterSidedefs(void)
 
 		if (ld->tripwire)
 		{
-			ld->blendmode = AST_ADD;
+			ld->blendmode = (subtractTripwire ? AST_SUBTRACT : AST_ADD);
 			ld->alpha = 0xff;
 		}