diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 2f97c173c..4447614d3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -18,6 +18,7 @@ set(SRB2_CORE_SOURCES
 	filesrch.c
 	g_game.c
 	g_input.c
+	g_splitscreen.c
 	hu_stuff.c
 	i_tcp.c
 	info.c
@@ -156,7 +157,13 @@ set(SRB2_CORE_GAME_SOURCES
 	p_telept.c
 	p_tick.c
 	p_user.c
+	k_battle.c
+	k_bheap.c
+	k_collide.c
 	k_kart.c
+	k_pathfind.c
+	k_pwrlv.c
+	k_waypoint.c
 
 	p_local.h
 	p_maputl.h
@@ -168,7 +175,13 @@ set(SRB2_CORE_GAME_SOURCES
 	p_slopes.h
 	p_spec.h
 	p_tick.h
+	k_battle.h
+	k_bheap.h
+	k_collide.h
 	k_kart.h
+	k_pathfind.h
+	k_pwrlv.h
+	k_waypoint.h
 )
 
 if(NOT (CMAKE_CXX_COMPILER_ID MATCHES "Clang"))
diff --git a/src/p_slopes.c b/src/p_slopes.c
index e623b6f19..03c1205f6 100644
--- a/src/p_slopes.c
+++ b/src/p_slopes.c
@@ -54,6 +54,13 @@ static void P_ReconfigureVertexSlope(pslope_t *slope)
 		max(max(abs(vec1.x), abs(vec1.y)), abs(vec1.z)),
 		max(max(abs(vec2.x), abs(vec2.y)), abs(vec2.z))
 	) >> (FRACBITS+5);
+
+	if (slope->extent == 0)
+	{
+		// Prevent divide by zero
+		slope->extent = 1;
+	}
+
 	vec1.x /= slope->extent;
 	vec1.y /= slope->extent;
 	vec1.z /= slope->extent;
diff --git a/src/p_spec.c b/src/p_spec.c
index 6debb5df2..95289b9a7 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -7164,9 +7164,15 @@ static void P_SpawnScrollers(void)
 	{
 		fixed_t dx = l->dx >> SCROLL_SHIFT; // direction and speed of scrolling
 		fixed_t dy = l->dy >> SCROLL_SHIFT;
+
+		fixed_t bx = 0;/* backside variants */
+		fixed_t by = 0;
+
 		INT32 control = -1, accel = 0; // no control sector or acceleration
 		INT32 special = l->special;
 
+		INT32 s;
+
 		// These types are same as the ones they get set to except that the
 		// first side's sector's heights cause scrolling when they change, and
 		// this linedef controls the direction and speed of the scrolling. The
@@ -7195,10 +7201,24 @@ static void P_SpawnScrollers(void)
 			control = (INT32)(sides[*l->sidenum].sector - sectors);
 		}
 
+		if (special == 507) // front and back scrollers
+		{
+			s  = l->sidenum[0];
+
+			dx = -(sides[s].textureoffset);
+			dy =   sides[s].rowoffset;
+
+			s  = l->sidenum[1];
+
+			if (s != 0xffff)
+			{
+				bx = -(sides[s].textureoffset);
+				by =   sides[s].rowoffset;
+			}
+		}
+
 		switch (special)
 		{
-			register INT32 s;
-
 			case 513: // scroll effect ceiling
 			case 533: // scroll and carry objects on ceiling
 				for (s = -1; (s = P_FindSectorFromLineTag(l, s)) >= 0 ;)
@@ -7251,6 +7271,18 @@ static void P_SpawnScrollers(void)
 					CONS_Debug(DBG_GAMELOGIC, "Line special 506 (line #%s) missing 2nd side!\n", sizeu1(i));
 				break;
 
+			case 507: // scroll front and backside of tagged lines
+				for (s = -1; (s = P_FindLineFromLineTag(l, s)) >= 0 ;)
+				{
+					if (s != (INT32)i)
+					{
+						Add_Scroller(sc_side, dx, dy, control, lines[s].sidenum[0], accel, 0);
+						if (lines[s].sidenum[1] != 0xffff)
+							Add_Scroller(sc_side, bx, by, control, lines[s].sidenum[1], accel, 0);
+					}
+				}
+				break;
+
 			case 500: // scroll first side
 				Add_Scroller(sc_side, FRACUNIT, 0, -1, lines[i].sidenum[0], accel, 0);
 				break;