diff --git a/src/experimental/tile_penrose3.scad b/src/experimental/tile_penrose3.scad
index 4a4fd647..3fdef3f1 100644
--- a/src/experimental/tile_penrose3.scad
+++ b/src/experimental/tile_penrose3.scad
@@ -1,31 +1,28 @@
-use <ptf/ptf_rotate.scad>;
-use <hull_polyline2d.scad>;
-
 function _subdivide(triangles) = 
 	[
 		for(tri = triangles)
-		let(
-			type = tri[0],
-			a = tri[1],
-			b = tri[2],
-			c = tri[3]
-		)
-		each (type == "OBTUSE" ? _sub_obtuse(a, b, c) : _sub_acute(a, b, c))
+		each (tri[0] == "OBTUSE" ? _sub_obtuse(tri[1]) : _sub_acute(tri[1]))
 	];
 
-function _sub_acute(a, b, c) =
+function _sub_acute(tri_shape) =
 	let(
+		a = tri_shape[0],
+		b = tri_shape[1],
+		c = tri_shape[2],
 		PHI = 1.618033988749895,
 		p = a + (b - a) / PHI
 	)
-	[["ACUTE", c, p, b], ["OBTUSE", p, c, a]];	
+	[["ACUTE", [c, p, b]], ["OBTUSE", [p, c, a]]];	
 	
-function _sub_obtuse(a, b, c) =
+function _sub_obtuse(tri_shape) =
 	let(
+		a = tri_shape[0],
+		b = tri_shape[1],
+		c = tri_shape[2],
 		PHI = 1.618033988749895,
 		r = b + (c - b) / PHI
 	) 
-	[["OBTUSE", r, c, a], each _sub_acute(b, a, r)];
+	[["OBTUSE", [r, c, a]], each _sub_acute([b, a, r])];
 
 function _penrose3(triangles, n, i = 0) = 
 	i == n ? triangles : _penrose3(_subdivide(triangles), n, i+ 1);
@@ -34,36 +31,34 @@ function tri2tile(type, tri) =
     let(
 		tri1 = tri[1],
 		tri2 = tri[2],
-	    c = (tri1 + tri2) / 2,
-		v = c - tri[0],
-		m = c + v
+		m = 2 * (tri1 + tri2) / 2 - tri[0]
 	)
-	[[type, each tri], [type, m, tri1, tri2]];
+	[[type, tri], [type, [m, tri1, tri2]]];
 
 function _zRotation(a) = 
     let(c = cos(a), s = sin(a))
-    [
-        [c, -s],
-        [s, c]
-    ]; 
+    [[c, -s], [s, c]]; 
 
 function tile_penrose3(n, triangles) = 
     let(
 		fn = 10,
-		a = 720 / fn,
-		tris = _penrose3(
-		    is_undef(triangles) ? 
-				let(shape_tri0 = [[1, 0], [1, 0] + ptf_rotate([-1, 0], -180 + a), [0, 0]])
-				[
-					for(i = [0:fn / 2 - 1]) 
-					let(m = _zRotation(i * a), t = [for(p = shape_tri0) m * p])
-					each tri2tile("OBTUSE", t)
-				] :
-            	[for(tri = triangles) each tri2tile(tri[0], [tri[1][1], tri[1][2], tri[1][0]])],
-		    n
-		)
+		a = 720 / fn
 	)
-    [for(t = tris) [t[0], [t[3], t[1], t[2]]]];
+    _penrose3(
+		is_undef(triangles) ? 
+		    // star
+			let(shape_tri0 = [[1, 0], [1, 0] + _zRotation(-180 + a) * [-1, 0], [0, 0]])
+			[
+				for(i = [0:fn / 2 - 1]) 
+				let(m = _zRotation(i * a), t = [for(p = shape_tri0) m * p])
+				each tri2tile("OBTUSE", t)
+			] :
+			[for(tri = triangles) each tri2tile(tri[0], tri[1])],
+		n
+	);
+
+use <ptf/ptf_rotate.scad>;
+use <polyline_join.scad>;
 
 module draw(tris, radius) {
 	for(t = tris) {
@@ -71,16 +66,15 @@ module draw(tris, radius) {
 		linear_extrude(.5)
 			polygon(t[1] * radius);
 		linear_extrude(1)
-		    hull_polyline2d(t[1] * radius, .1);
+		    polyline_join(t[1] * radius)
+			    circle(.1);
 	}
 }
 
 radius = 10;
 $fn = 12;
 
-draw(tile_penrose3(5, [
-    ["OBTUSE", [ptf_rotate([2, 0], 108), [0, 0], [2, 0]]]
-]), radius);
+draw(tile_penrose3(5, [["OBTUSE", [[0, 0], [1, 0], ptf_rotate([1, 0], 108)]]]), radius);
 
 translate([40, 0])
     draw(tile_penrose3(0), radius);