diff --git a/buildglyphs.patel b/buildglyphs.patel
index 94fa575..cc29aef 100644
--- a/buildglyphs.patel
+++ b/buildglyphs.patel
@@ -3,6 +3,8 @@ define Stroke [require './support/stroke'].Stroke
 define tp [require './support/transform'].transformPoint
 define inverse [require './support/transform'].inverse
 
+define libspiro : require 'libspiro-js'
+
 ### COMMON FUNCTIONS
 
 define [mix a b p] : a + [b - a] * p
@@ -211,6 +213,53 @@ define [buildFont para recursive] : begin {
 	set font.'OS/2'.sxHeight          XH
 	set font.post.italicAnvle         [0 - para.italicangle]
 	
+	### Spiro constructions
+	define [flatten knots] : begin {
+		local a ()
+		foreach p [items-of knots] : piecewise {
+			[p <@ Array] : set a : a.concat [flatten p]
+			true         : a.push p
+		}
+		return a
+	}
+	define [afInterpolate before after args] : G2 [mix before.x after.x args.rx] [mix before.y after.y args.ry] VIRTUAL
+	define [G4 x y f] (.x x .y y .type 'g4' .af f)
+	define [G2 x y f] (.x x .y y .type 'g2' .af f)
+	define [LEFT x y f] (.x x .y y .type 'left' .af f)
+	define [RIGHT x y f] (.x x .y y .type 'right' .af f)
+	define [CLOSE f] (.type 'close' .af f)
+	define [PREPARE f] (.type 'prepare' .af f)
+	define [WIDTHS l r] : lambda [] : this.set-width l r
+	define [VIRTUAL] : this.points.[this.points.length - 1].subdivided = true
+	define [INTERPOLATE rx ry] (.type 'interpolate' .rx rx .ry ry .af afInterpolate)
+	define [spiro] : begin {
+		local s : new Stroke
+		s.set-transform globalTransform
+		local knots : ().slice.call arguments 0
+		local closed false
+		local lastaf
+		if [knots.0 && knots.0.type === 'prepare'] : begin {
+			knots.0.af.call s
+			set knots : knots.slice 1
+		}
+		if [knots.[knots.length - 1] && knots.[knots.length - 1].type === 'close'] : begin {
+			set closed true
+			set lastaf knots.[knots.length - 1].af
+			set knots : knots.slice 0 [-1]
+		}
+		set knots : flatten knots
+		if closed : knots.push knots.0
+		foreach j [range 0 knots.length] : if [knots.(j) && knots.(j).type === 'interpolate'] : begin {
+			set knots.(j) : knots.(j).af.call s knots.[j - 1] knots.[j + 1] knots.(j)
+		}
+		if closed : knots.pop
+		set knots : flatten knots
+		s.set-samples 1
+		libspiro.spiroToBezierOnContext knots closed s
+		if lastaf : lastaf.call s
+		return s
+	}
+	
 	### Necessary macros
 	define-macro glyph-construction : syntax-rules {
 		@`[glyph-construction @::steps] ('.syntactic-closure' @`[lambda [] [begin {
diff --git a/glyphs/common-shapes.patel b/glyphs/common-shapes.patel
index 79ba085..e75bfc0 100644
--- a/glyphs/common-shapes.patel
+++ b/glyphs/common-shapes.patel
@@ -221,16 +221,30 @@ define [smallo u d l r _width _sma _smb] : glyph-construction {
 	local mc : OMIDCOR * width
 	if [u - d > sma + smb] {
 		then : begin {
-			include : create-stroke
-				:.set-transform globalTransform
-				:.start-from [middle - mc] [u - O]
-				:.set-width width 0
-				:.arc-hv-to [l + O] [u - sma]
-				:.line-to  [l + O] [d + smb]
-				:.arc-vh-to [middle + mc] [d + O]
-				:.arc-hv-to [r - O] [d + sma]
-				:.line-to  [r - O] [u - smb]
-				:.arc-vh-to [middle - mc] [u - O]
+			include : spiro {
+				PREPARE : WIDTHS width 0
+				G4 [middle - mc] [u - O]
+				INTERPOLATE 0.5 0.11
+				LEFT [l + O] [u - sma]
+				RIGHT [l + O] [d + smb]
+				INTERPOLATE 0.5 0.89
+				G4 [middle + mc] [d + O]
+				INTERPOLATE 0.5 0.11
+				LEFT [r - O] [d + sma]
+				RIGHT [r - O] [u - smb]
+				INTERPOLATE 0.5 0.89
+				CLOSE
+			}
+#			include : create-stroke
+#				:.set-transform globalTransform
+#				:.start-from [middle - mc] [u - O]
+#				:.set-width width 0
+#				:.arc-hv-to [l + O] [u - sma]
+#				:.line-to  [l + O] [d + smb]
+#				:.arc-vh-to [middle + mc] [d + O]
+#				:.arc-hv-to [r - O] [d + sma]
+#				:.line-to  [r - O] [u - smb]
+#				:.arc-vh-to [middle - mc] [u - O]
 		}
 		else : begin {
 			local ymiddlea : mix d u [smb / [sma + smb]]
diff --git a/support/stroke.patel b/support/stroke.patel
index a6b5eb1..5dca78a 100644
--- a/support/stroke.patel
+++ b/support/stroke.patel
@@ -29,6 +29,8 @@ define [Stroke] : begin {
 		.x 0
 		.y 0
 	)
+	this.defaultd1 = 0
+	this.defaultd2 = 0
 	return this
 }
 define Stroke.is : object {
@@ -47,8 +49,16 @@ define [Stroke.bindParameters para] : begin {
 }
 define [Stroke.prototype.set-width d1 d2] : begin {
 	local point this.points`[this.points.length - 1]
-	point.d1 = d1
-	point.d2 = d2
+	if point {
+		then {
+			point.d1 = d1
+			point.d2 = d2
+		}
+		else {
+			this.defaultd1 = d1
+			this.defualtd2 = d2
+		}
+	}
 	return this
 }
 define [Stroke.prototype.heads-to x y] : begin {
@@ -126,13 +136,14 @@ define [computeOffsetPoint curve t j sl foffset fpdx fpdy] : begin {
 }
 
 define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
-	local d1s ([set d1 [if [this.points.0.d1 >= 0] this.points.0.d1 d1]])
-	local d2s ([set d2 [if [this.points.0.d2 >= 0] this.points.0.d2 d2]])
+	local d1s ([set d1 [if [this.points.0.d1 >= 0] this.points.0.d1 this.defaultd1]])
+	local d2s ([set d2 [if [this.points.0.d2 >= 0] this.points.0.d2 this.defaultd2]])
 	local pdxs (0)
 	local pdys (0)
 	local ts (0)
+	local brk ()
 	
-	local samples : fallback _samples this.samples SAMPLES
+	local minSamples : fallback _samples this.samples SAMPLES
 	local shapes ()
 	local subSegments ()
 	
@@ -146,6 +157,7 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 				arcLengthSofar = arcLengthSofar + [seg.length]
 				if [not p1.subdivided] : begin {
 					ts.push arcLengthSofar
+					brk.[subSegments.length - 1] = true
 					d1s.push : set d1 [if [p1.d1 >= 0] p1.d1 d1]
 					d2s.push : set d2 [if [p1.d2 >= 0] p1.d2 d2]
 					local normalpt : seg.normal 1
@@ -161,6 +173,7 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 				arcLengthSofar = arcLengthSofar + [seg.length]
 				if [not p3.subdivided] : begin {
 					ts.push arcLengthSofar
+					brk.[subSegments.length - 1] = true
 					d1s.push : set d1 [if [p3.d1 >= 0] p3.d1 d1]
 					d2s.push : set d2 [if [p3.d2 >= 0] p3.d2 d2]
 					local normalpt : seg.normal 1
@@ -176,6 +189,7 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 				arcLengthSofar = arcLengthSofar + [seg.length]
 				if [not p2.subdivided] : begin {
 					ts.push arcLengthSofar
+					brk.[subSegments.length - 1] = true
 					d1s.push : set d1 [if [p2.d1 >= 0] p2.d1 d1]
 					d2s.push : set d2 [if [p2.d2 >= 0] p2.d2 d2]
 					local normalpt : seg.normal 1
@@ -203,12 +217,14 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 		local curve subSegments`j
 		local segLength : curve.length
 		local segLengths (0)
+		
+		local samples : Math.max minSamples : Math.ceil : segLength / 150
+		
 		foreach sample [range 1 till samples] : begin {
 			segLengths.push : curve.split 0 [sample / samples] :.length
 		}
 		left.push [begin [local last [computeOffsetPoint curve arcLengthSofar arcLengthSofar segLength f1 fpdx fpdy]] (.x last.x .y last.y .onCurve true)]
 		right.push [begin [local last [computeOffsetPoint curve arcLengthSofar arcLengthSofar segLength f2 fpdx fpdy]] (.x last.x .y last.y .onCurve true)]
-
 		foreach sample [range 0 samples] : begin {
 			local t : arcLengthSofar + segLengths.(sample)
 			local tn : arcLengthSofar + segLengths.[sample + 1]
@@ -250,6 +266,13 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 			}]
 		}
 		arcLengthSofar = arcLengthSofar + segLength
+		if brk.(j) : begin {
+			shapes.push : left.concat [right.reverse]
+			set left ()
+			set right ()
+		}
+	}
+	if [left.length + right.length > 2] : begin {
 		shapes.push : left.concat [right.reverse]
 		set left ()
 		set right ()
@@ -257,13 +280,14 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 
 	return : shapes.map : function [shape] : begin {
 		# Remove duplicate points
-		for [local j] [j < shape.length - 1] [inc j] : begin {
+		for [local j 0] [j < shape.length - 1] [inc j] : begin {
 			local p0 shape.(j)
 			local p1 shape.[j + 1]
-			if [p0.onCurve && p1.onCurve && p0.x === p1.x && p0.y === p1.y] : set p1.removable true
+			if [p0.onCurve && p1.onCurve && [Math.abs : p0.x - p1.x] <= 0.1 && [Math.abs : p0.y - p1.y] <= 0.1] : set p1.removable true
 		}
-		# Remove colinear oncurve points
 		set shape : shape.filter : function [point] [point && [not point.removable]]
+		
+		# Remove colinear oncurve points
 		for [local j 0] [j < shape.length - 1] [inc j] : begin {
 			local p0 shape`j
 			local still true
@@ -279,6 +303,7 @@ define [Stroke.prototype.to-outline d1 d2 _samples straight] : begin {
 			set j [k - 1]
 		}
 		set shape : shape.filter : function [point] [point && [not point.removable]]
+		
 		# Remove removable midpoints
 		for [local j 1] [j < shape.length - 2] [inc j] : begin {
 			local p0 shape`j