diff --git a/engine/physics/src/minimum_difference.rs b/engine/physics/src/minimum_difference.rs
index 6f63d4ca..538bb0e5 100644
--- a/engine/physics/src/minimum_difference.rs
+++ b/engine/physics/src/minimum_difference.rs
@@ -27,16 +27,6 @@ enum Simplex2_4{
 	Simplex3(Simplex<3>),
 	Simplex4(Simplex<4>),
 }
-impl core::ops::Index<usize> for Simplex2_4{
-	type Output=MinkowskiVert;
-	fn index(&self,index:usize)->&Self::Output{
-		match self{
-			Simplex2_4::Simplex2(s)=>&s[index],
-			Simplex2_4::Simplex3(s)=>&s[index],
-			Simplex2_4::Simplex4(s)=>&s[index],
-		}
-	}
-}
 
 /*
 local function absDet(r, u, v, w)
@@ -555,12 +545,12 @@ pub fn contains_point(mesh:&MinkowskiMesh,point:Planar64Vec3)->bool{
 	const ENABLE_FAST_FAIL:bool=true;
 	minimum_difference::<ENABLE_FAST_FAIL,_>(mesh,point,
 		// on_exact
-		|simplex,direction|{
+		|last_pos,direction|{
 			// local norm = direction.unit
 			// local dist = a:Dot(norm)
 			// local hits = -dist < radiusP + radiusQ
 			// return hits
-			(mesh.vert(simplex[1])+point).dot(direction).is_positive()
+			(last_pos+point).dot(direction).is_positive()
 		},
 		// on_escape
 		|_simplex|{
@@ -575,7 +565,7 @@ pub fn closest_fev(mesh:&MinkowskiMesh,point:Planar64Vec3)->Topology{
 	const ENABLE_FAST_FAIL:bool=false;
 	minimum_difference::<ENABLE_FAST_FAIL,_>(mesh,point,
 		// on_exact
-		|simplex,_direction|Topology{simplex},
+		|_last_pos,_direction|unimplemented!(),
 		// on_escape
 		|simplex|{
 			// local norm, dist, u0, u1, v0, v1, w0, w1 = expand(queryP, queryQ, a0, a1, b0, b1, c0, c1, d0, d1, 1e-5)
@@ -595,7 +585,7 @@ pub fn closest_fev(mesh:&MinkowskiMesh,point:Planar64Vec3)->Topology{
 fn minimum_difference<const ENABLE_FAST_FAIL:bool,T>(
 	mesh:&MinkowskiMesh,
 	point:Planar64Vec3,
-	on_exact:impl FnOnce(Simplex2_4,Planar64Vec3)->T,
+	on_exact:impl FnOnce(Planar64Vec3,Planar64Vec3)->T,
 	on_escape:impl FnOnce(Simplex<4>)->T,
 	on_fast_fail:impl FnOnce()->T,
 )->T{
@@ -608,8 +598,10 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T>(
 	if direction==vec3::zero(){
 		direction=choose_any_direction();
 	}
-	let new_point=mesh.farthest_vert(direction);
-	let Reduced{dir:mut direction,simplex:mut simplex_small}=reduce1([new_point],mesh,point);
+	let last_point=mesh.farthest_vert(direction);
+	// this represents the 'a' value in the commented code
+	let mut last_pos=mesh.vert(last_point);
+	let Reduced{dir:mut direction,simplex:mut simplex_small}=reduce1([last_point],mesh,point);
 
 	// exitRadius = testIntersection and 0 or exitRadius or 1/0
 	// for _ = 1, 100 do
@@ -630,10 +622,10 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T>(
 		// if
 		// 	direction:Dot(next_point - a) <= 0 or
 		// 	absDet(next_point, a, b, c) < 1e-6
-		if !direction.dot(next_pos-mesh.vert(simplex_big[1])).is_positive()
+		if !direction.dot(next_pos-last_pos).is_positive()
 		||simplex_big.det_is_zero(mesh){
 			// Found enough information to compute the exact closest point.
-			return on_exact(simplex_big,direction);
+			return on_exact(last_pos,direction);
 		}
 
 		// direction, a0, a1, b0, b1, c0, c1, d0, d1 = reduceSimplex(new_point_p, new_point_q, a0, a1, b0, b1, c0, c1)
@@ -649,5 +641,8 @@ fn minimum_difference<const ENABLE_FAST_FAIL:bool,T>(
 				simplex_small=reduced.simplex;
 			},
 		}
+
+		// next loop this will be a
+		last_pos=next_pos;
 	}
 }