I changed letter D to fit in an 8x8 grid nicely.

typeface.py

@@ -12,6 +12,8 @@
 from turtle import *
 from math import sqrt
 
+size=40
+
 def draw_letter_a(unit):
     pass
 
@@ -22,7 +24,45 @@ def draw_letter_c(unit):
     pass
 
 def draw_letter_d(unit):
-    pass
+    penup()
+    forward(size)
+    pendown()
+    forward(size*4)
+    left(45)
+    forward(size*sqrt(2))
+    forward(size*sqrt(2))
+    left(45)
+    forward(size*4)
+    left(45)
+    forward(size*sqrt(2))
+    forward(size*sqrt(2))
+    left(45)
+    forward(size*4)
+    left(90)
+    forward(size*8)
+    left(90)
+    penup()
+    forward(size*2)
+    left(90)
+    forward(size*2)
+    pendown()
+    forward(size*4)
+    right(90)
+    forward(size)
+    right(45)
+    forward(size*sqrt(2))
+    right(45)
+    forward(size*2)
+    right(45)
+    forward(size*sqrt(2))
+    right(45)
+    forward(size)
+    left(90)
+    penup()
+    forward(size*2)
+    right(90)
+    forward(size*3)
+    right(180)
 
 def draw_letter_e(unit):
     pass