diff --git a/game/reconstructed/btl4vid.cpp b/game/reconstructed/btl4vid.cpp
index 66f8deb..bad21f8 100644
--- a/game/reconstructed/btl4vid.cpp
+++ b/game/reconstructed/btl4vid.cpp
@@ -227,9 +227,26 @@ void
 			// to terrain).
 			{
 				extern Entity *gBTTerrainEntity;
+				// The boresight ground/structure pick needs a non-null world Entity to
+				// cite in mech+0x388 (the geometry rides in the pick POINT; the entity is
+				// only the non-mech designation -- the decomp's HudSimulation handles a
+				// target with no damage-zone table, part_013.c:5620).  Previously this
+				// required a TERRAIN-derived entity, but maps whose world geometry is
+				// buildings/cultural/props (class-42, NOT Terrain-derived) captured
+				// nothing -> gBTTerrainEntity stayed 0 -> the ground pick was skipped
+				// (mech4.cpp:4372) -> only mechs were targetable/firable (task #50
+				// regression: LAST.EGG rewrite lost its Terrain entity).  This `default`
+				// case is world-geometry ONLY (mechs route elsewhere), so capture the
+				// first entity reaching it -- preferring a real Terrain, else any world
+				// entity (building/prop/landmark) as the non-mech pick sentinel.
 				if (gBTTerrainEntity == 0
-					&& entity->IsDerivedFrom(*Terrain::GetClassDerivations()))
-					gBTTerrainEntity = entity;
+					|| !gBTTerrainEntity->IsDerivedFrom(*Terrain::GetClassDerivations()))
+				{
+					if (entity->IsDerivedFrom(*Terrain::GetClassDerivations()))
+						gBTTerrainEntity = entity;			// prefer a true Terrain entity
+					else if (gBTTerrainEntity == 0)
+						gBTTerrainEntity = entity;			// else the first world entity
+				}
 			}
 			DPLRenderer::MakeEntityRenderables(
 				entity, model_resource, view_type);
diff --git a/game/reconstructed/btvisgnd.cpp b/game/reconstructed/btvisgnd.cpp
index 55ec007..5ec4ded 100644
--- a/game/reconstructed/btvisgnd.cpp
+++ b/game/reconstructed/btvisgnd.cpp
@@ -53,6 +53,7 @@ struct VgMesh
 {
 	std::vector<VgTri> tris;
 	float minx, maxx, minz, maxz;		// model-local XZ bound
+	float miny, maxy;					// model-local Y bound (dome vs flat-ground test)
 };
 
 struct VgInst
@@ -89,8 +90,8 @@ int LoadMeshFor(const char *resource_name)
 	if (LoadBgfFile(file, data) && data.ok && !data.indices.empty())
 	{
 		VgMesh m;
-		m.minx = m.minz = 1e9f;
-		m.maxx = m.maxz = -1e9f;
+		m.minx = m.minz = m.miny = 1e9f;
+		m.maxx = m.maxz = m.maxy = -1e9f;
 		// The loader emits DOUBLE-SIDED triangles: emitTri pushes (a,b,c) then
 		// (a,c,b) -- 6 indices per source triangle.  Take the forward one.
 		for (size_t i = 0; i + 5 < data.indices.size(); i += 6)
@@ -100,17 +101,33 @@ int LoadMeshFor(const char *resource_name)
 			const BgfVtx &C = data.verts[data.indices[i + 2]];
 			VgTri t = { A.x, A.y, A.z, B.x, B.y, B.z, C.x, C.y, C.z };
 			m.tris.push_back(t);
-			float xs[3] = { A.x, B.x, C.x }, zs[3] = { A.z, B.z, C.z };
+			float xs[3] = { A.x, B.x, C.x }, zs[3] = { A.z, B.z, C.z }, ys[3] = { A.y, B.y, C.y };
 			for (int k = 0; k < 3; ++k)
 			{
 				if (xs[k] < m.minx) m.minx = xs[k];
 				if (xs[k] > m.maxx) m.maxx = xs[k];
 				if (zs[k] < m.minz) m.minz = zs[k];
 				if (zs[k] > m.maxz) m.maxz = zs[k];
+				if (ys[k] < m.miny) m.miny = ys[k];
+				if (ys[k] > m.maxy) m.maxy = ys[k];
 			}
 		}
 		if (!m.tris.empty())
 		{
+			if (getenv("BT_GROUND_LOG"))
+			{
+				float miny = 1e9f, maxy = -1e9f;
+				for (size_t j = 0; j < m.tris.size(); ++j)
+				{
+					const VgTri &t = m.tris[j];
+					const float ys[3] = { t.ay, t.by, t.cy };
+					for (int k = 0; k < 3; ++k)
+					{ if (ys[k] < miny) miny = ys[k]; if (ys[k] > maxy) maxy = ys[k]; }
+				}
+				DEBUG_STREAM << "[visgnd] mesh '" << key << "' tris=" << m.tris.size()
+					<< " x[" << m.minx << "," << m.maxx << "] z[" << m.minz << "," << m.maxz
+					<< "] y[" << miny << "," << maxy << "]\n" << std::flush;
+			}
 			gMeshes.push_back(m);
 			idx = (int)gMeshes.size() - 1;
 		}
@@ -156,11 +173,31 @@ bool BuildTables()
 
 		ResourceDescription *rd = rf->FindResourceDescription(rid);
 		if (rd == 0) continue;
-		if (SkippedName(rd->resourceName)) { ++skipped; continue; }
 
 		int mi = LoadMeshFor(rd->resourceName);
 		if (mi < 0) { ++skipped; continue; }
 
+		// GEOMETRY-AWARE skip: the name filter (sky/backdrop) is right for a high
+		// vertical DOME, but arena1's ground is a 10000x10000 FLAT plane at y=0
+		// misnamed "sky" -- name-skipping it removed the only groundable geometry
+		// (task #50: buildings/ground stopped moving the range axis).  Keep a
+		// name-skipped mesh IF it is a wide, near-flat, near-ground plane (the
+		// arena floor); still skip true domes / tall vertical backdrops.
+		if (SkippedName(rd->resourceName))
+		{
+			const VgMesh &gm = gMeshes[mi];
+			const float yext = gm.maxy - gm.miny;
+			const float xext = gm.maxx - gm.minx, zext = gm.maxz - gm.minz;
+			const bool flatWideGround =
+				(yext < 200.0f) && (xext > 500.0f) && (zext > 500.0f) && (gm.miny < 200.0f);
+			if (getenv("BT_GROUND_LOG"))
+				DEBUG_STREAM << "[visgnd] name-skip '" << rd->resourceName
+					<< "' yext=" << yext << " xz=" << xext << "x" << zext
+					<< " miny=" << gm.miny << " -> keepAsGround=" << (flatWideGround?1:0)
+					<< "\n" << std::flush;
+			if (!flatWideGround) { ++skipped; continue; }
+		}
+
 		VgInst inst;
 		inst.mesh = mi;
 		inst.px = pos[0]; inst.py = pos[1]; inst.pz = pos[2];
diff --git a/game/reconstructed/mech4.cpp b/game/reconstructed/mech4.cpp
index 1e4ed43..9578090 100644
--- a/game/reconstructed/mech4.cpp
+++ b/game/reconstructed/mech4.cpp
@@ -4397,9 +4397,28 @@ void
 				MECH_TARGET_SUBIDX(this) = -1;
 				MECH_TARGET_POS(this)    = pickPoint;	// beam endpoint = the pick
 			}
+			else if (gBTTerrainEntity != 0)
+			{
+				// FIRE-AT-NOTHING (authentic, decomp part_013.c:7727): the pod fired
+				// freely at empty space -- the discharge gate is 0x388!=0 (the boresight
+				// always DESIGNATES a point, not a manual mech lock).  When nothing pickable
+				// is hit (a level shot flies over the flat ground, or open sky), designate a
+				// MAX-RANGE point using the world sentinel so the weapon discharges to max
+				// range.  Sentinel has no damage-zone table -> no aimed-zone damage, no lock
+				// ring (mechs only), per HudSimulation part_013.c:5620.
+				MECH_TARGET_ENTITY(this) = gBTTerrainEntity;
+				MECH_TARGET_SUBIDX(this) = -1;
+				Point3D farPt;
+				farPt.x = rs[0] + rd[0] * 1200.0f;	// 1200 = HUD range default (0x44960000)
+				farPt.y = rs[1] + rd[1] * 1200.0f;
+				farPt.z = rs[2] + rd[2] * 1200.0f;
+				MECH_TARGET_POS(this) = farPt;
+				targetReticle.targetEntity    = gBTTerrainEntity;
+				targetReticle.rayIntersection = farPt;
+			}
 			else
 			{
-				MECH_TARGET_ENTITY(this) = 0;			// sky: no target, no discharge
+				MECH_TARGET_ENTITY(this) = 0;			// no world sentinel -> no target
 				MECH_TARGET_SUBIDX(this) = -1;
 			}
 		}
@@ -4835,7 +4854,8 @@ void
 				DEBUG_STREAM << "[target] aim=(" << gBTAimX << "," << gBTAimY << ")"
 					<< (victim != 0 ? "  MECH under boresight (aimed)"
 						: (pickTarget != 0 ? "  terrain downrange (beam at scenery)"
-										   : "  sky (no target, no discharge)"))
+						: (MECH_TARGET_ENTITY(this) != 0 ? "  fire-at-nothing (max-range designate)"
+										   : "  no target (no world sentinel)")))
 					<< "  range=" << range
 					<< (anyWeaponInRange ? "  IN WEAPON RANGE" : "")
 					<< "  [mechPicks=" << gAimHits << " groundPicks=" << gAimGround