diff --git a/restoration/source410/BT/MECH.CPP b/restoration/source410/BT/MECH.CPP
index fbe89f5b..3583acf4 100644
--- a/restoration/source410/BT/MECH.CPP
+++ b/restoration/source410/BT/MECH.CPP
@@ -1523,6 +1523,9 @@ void
 	// Integrate position and commit the Origin to the world transform.
 	//-----------------------------------------------------------------------
 	//
+	Point3D
+		frame_start_position = localOrigin.linearPosition;
+
 	localOrigin.linearPosition.AddScaled(
 		localOrigin.linearPosition,
 		worldLinearVelocity,
@@ -1590,6 +1593,94 @@ void
 		}
 	}
 
+	//
+	//-----------------------------------------------------------------------
+	// COLLISIONS -- the response half of the master performance's ground
+	// model (binary @4aa6cf-4aab0b).  Walls block by FULL FRAME REJECTION,
+	// never by slide or climb: any blocking contact restores the
+	// start-of-frame position and zeroes the velocity.  The crash itself
+	// HURTS -- the accumulated collision Damage is dispatched at OUR OWN
+	// mech, zone -1 (the cylinder lottery), which is what makes wall-
+	// grinding self-limiting.  And a hard enough hit (|v|^2 > 40, the
+	// binary's @0x4ab184 threshold) staggers the mech: both gait channels
+	// bind the bump clip (slot 0x20) and recover to Standing at its end.
+	//
+	// Guarded on the collision assistant: the engine's GetCurrentCollisions
+	// walks it unchecked, and only the viewpoint mech gets one
+	// (StartCollisionAssistant, BTL4APP.CPP:409).
+	//
+	// STAGED deltas, named: the crushable-CulturalIcon sentinel (0.00123f
+	// -- the move stands, gyro crunch) needs the Mech::ProcessCollision
+	// override, a later increment; the gyro crunch feed itself is with it;
+	// and the collisionState audio push waits on the same override's
+	// contact accumulation.
+	//-----------------------------------------------------------------------
+	//
+	if (
+		collisionAssistant != NULL &&
+		GetCollisionVolumeCount() > 0 &&
+		collisionVolume != NULL
+	)
+	{
+		Vector3D
+			impact_velocity = worldLinearVelocity;
+		BoxedSolidCollisionList
+			*collisions = GetCurrentCollisions();
+		Damage
+			collision_damage;
+
+		if (collisions != NULL)
+		{
+			ProcessCollisionList(
+				collisions, time_slice, frame_start_position,
+				&collision_damage);
+		}
+
+		if (collision_damage.damageAmount > 0.0f)
+		{
+			worldLinearVelocity = Vector3D(0.0f, 0.0f, 0.0f);
+			localOrigin.linearPosition = frame_start_position;
+			localToWorld = localOrigin;
+			MoveCollisionVolume();
+
+			Entity::TakeDamageMessage
+				crash(
+					Entity::TakeDamageMessageID,
+					sizeof(Entity::TakeDamageMessage),
+					GetEntityID(),
+					-1,
+					collision_damage
+				);
+			Dispatch(&crash);
+
+			Scalar
+				impact_squared =
+					impact_velocity.x * impact_velocity.x +
+					impact_velocity.y * impact_velocity.y +
+					impact_velocity.z * impact_velocity.z;
+			if (
+				impact_squared > 40.0f &&
+				animationClips[0x20] != ResourceDescription::NullResourceID &&
+				legStateAlarm.GetLevel() != 0x20
+			)
+			{
+				SetLegAnimation(0x20);
+				SetBodyAnimation(0x20);
+				ForceUpdate(1);
+				ForceUpdate(0x20);
+			}
+
+			if (getenv("BT_MECH_LOG"))
+			{
+				DEBUG_STREAM << "[crash] BLOCK dmg="
+					<< collision_damage.damageAmount
+					<< " iv2=" << impact_squared
+					<< (impact_squared > 40.0f ? " KNOCKDOWN" : "")
+					<< endl << flush;
+			}
+		}
+	}
+
 	if (getenv("BT_MECH_LOG"))
 	{
 		static Scalar reportAccum = 0.0f;