diff --git a/boxes/servos.py b/boxes/servos.py
index 606b4f3e..08d1c77c 100644
--- a/boxes/servos.py
+++ b/boxes/servos.py
@@ -1,14 +1,14 @@
+from __future__ import annotations
+
 import math
 
 import boxes.vectors
 
 
 class EyeEdge(boxes.edges.FingerHoleEdge):
-
     char = "m"
 
-    def __init__(self, boxes, servo, fingerHoles=None, driven=False,
-                 outset=False, **kw) -> None:
+    def __init__(self, boxes, servo, fingerHoles=None, driven: bool = False, outset: bool = False, **kw) -> None:
         self.servo = servo
         self.outset = outset
         self.driven = driven
@@ -20,18 +20,18 @@ def __call__(self, length, bedBolts=None, bedBoltSettings=None, **kw):
 
         pos_axle = self.servo.hinge_depth()
         self.ctx.save()
-        self.hole(length/2.0, -pos_axle,
-                  self.servo.axle/2.0 if self.driven else
-                  self.servo.servo_axle/2.0)
+        self.hole(length / 2.0,
+                  -pos_axle,
+                  self.servo.axle / 2.0 if self.driven else self.servo.servo_axle / 2.0)
         if self.outset:
-            self.fingerHoles(t, self.thickness / 2, length-2*t, 0)
+            self.fingerHoles(t, self.thickness / 2, length - 2 * t, 0)
         else:
             self.fingerHoles(0, self.thickness / 2, length, 0)
         self.ctx.restore()
         r = self.servo.servo_axle * 2
-        a, l = boxes.vectors.tangent(length/2, pos_axle, r)
+        a, l = boxes.vectors.tangent(length / 2, pos_axle, r)
         angle = math.degrees(a)
-        self.polyline(0, -angle, l, (2*angle, r), l, -angle, 0)
+        self.polyline(0, -angle, l, (2 * angle, r), l, -angle, 0)
 
     def startwidth(self) -> float:
         return self.fingerHoles.settings.thickness
@@ -39,37 +39,35 @@ def startwidth(self) -> float:
     def margin(self) -> float:
         return self.servo.hinge_depth() + self.fingerHoles.settings.thickness + self.servo.servo_axle * 2
 
-def buildEdges(boxes, servo, chars="mMnN"):
+
+def buildEdges(boxes, servo, chars: str = "mMnN"):
     result = {}
     for n, char in enumerate(chars):
-        e = EyeEdge(boxes, servo, outset=(n<2), driven=(n % 2))
+        e = EyeEdge(boxes, servo, outset=(n < 2), driven=((n % 2) == 1))
         e.char = char
         result[char] = e
     return result
 
-class ServoArg:
 
-    def __init__(self, includenone=False) -> None:
+class ServoArg:
+    def __init__(self, includeNone: bool = False) -> None:
         self.servos = ["Servo9g"]
-        if includenone:
+        if includeNone:
             self.servos[0:0] = ["none"]
 
-    def __call__(self, arg):
+    def __call__(self, arg) -> str:
         return str(arg)
 
-    def choices(self):
+    def choices(self) -> list[str]:
         return [name for name in self.servos]
 
-    def html(self, name, default, translate):
-        options = "\n".join(
-            """<option value="%s"%s>%s</option>""" %
-             (name, ' selected="selected"' if name == default else "",
-              name) for name in self.servos)
+    def html(self, name: str, default: str, translate) -> str:
+        options = "\n".join("""<option value="{}"{}>{}</option>""".format(name, ' selected="selected"' if name == default else "", name) for name in self.servos)
         return f"""<select name="{name}" size="1">\n{options}</select>\n"""
 
 
 class Servo:
-    def __init__(self, boxes, axle=3) -> None:
+    def __init__(self, boxes, axle: float = 3) -> None:
         self.boxes = boxes
         self.axle = axle
         self._edges = buildEdges(boxes, self)
@@ -77,46 +75,47 @@ def __init__(self, boxes, axle=3) -> None:
     def edges(self, edges):
         return [self._edges.get(e, e) for e in edges]
 
-class Servo9g(Servo):
 
-    height = 22.5
-    length = 28.0 # one tab in the wall
-    width = 12.0
-    axle_pos = 6.0
-    servo_axle = 4.6 # 6.9 for servo arm
+class Servo9g(Servo):
+    height: float = 22.5
+    length: float = 28.0  # one tab in the wall
+    width: float = 12.0
+    axle_pos: float = 6.0
+    servo_axle: float = 4.6  # 6.9 for servo arm
 
-    def top(self, x=0.0, y=0.0, angle=90.0):
+    def top(self, x: float = 0.0, y: float = 0.0, angle: float = 90.0) -> None:
         self.boxes.moveTo(x, y, angle)
         self.boxes.hole(6, 0, 6)
         self.boxes.hole(12, 0, 3)
 
-    def bottom(self, x=0.0, y=0.0, angle=90.0):
+    def bottom(self, x: float = 0.0, y: float = 0.0, angle: float = 90.0) -> None:
         self.boxes.moveTo(x, y, angle)
-        self.boxes.hole(6, 0, self.axle/2.0)
+        self.boxes.hole(6, 0, self.axle / 2.0)
 
-    def front(self, x=0.0, y=0.0, angle=90.0):
+    def front(self, x: float = 0.0, y: float = 0.0, angle: float = 90.0) -> None:
         self.boxes.moveTo(x, y, angle)
         self.boxes.rectangularHole(5.4, 0, 2.4, 12)
         self.boxes.rectangularHole(17, 0, 4, 16)
 
-    def hinge_width(self):
+    def hinge_width(self) -> float:
         return self.height + self.boxes.thickness + 4.5
 
-    def hinge_depth(self):
-        return self.height # XXX
+    def hinge_depth(self) -> float:
+        return self.height  # XXX
+
 
 class Servo9gt(Servo9g):
     height = 35
 
-    def top(self, x=0.0, y=0.0, angle=90.0):
+    def top(self, x: float = 0.0, y: float = 0.0, angle: float = 90.0) -> None:
         self.boxes.moveTo(x, y, angle)
         self.boxes.hole(6, 0, 6)
         self.boxes.hole(12, 0, 5)
 
-    def bottom(self, x=0.0, y=0.0, angle=90.0):
+    def bottom(self, x: float = 0.0, y: float = 0.0, angle: float = 90.0) -> None:
         self.boxes.moveTo(x, y, angle)
         self.boxes.hole(6, 0, self.axle)
 
-    def front(self, x=0.0, y=0.0, angle=90.0):
+    def front(self, x: float = 0.0, y: float = 0.0, angle: float = 90.0) -> None:
         self.boxes.moveTo(x, y, angle)
         self.boxes.rectangularHole(5.4, 0, 2.4, 12)