diff --git a/tilde-train.py b/tilde-train.py
index 21d8fa6..2251870 100755
--- a/tilde-train.py
+++ b/tilde-train.py
@@ -1,138 +1,147 @@
 #!/usr/bin/env python3
 
-##  _   _ _    _      _            _      
-## | |_(_) |__| |___ | |_ _ _ __ _(_)_ _  
-## |  _| | / _` / -_)|  _| '_/ _` | | ' \ 
-## \__|_|_\__,_\___(_)__|_| \__,_|_|_||_|
-##
-## tilde.train is an instance of TerminalTrain.  It was originally developed
-## by cmccabe on tilde.town but is now maintained in tildegit with the main
-## development ocurring on rawtext.club.
-##
-## If you want to contribute to code improvement, or if you have suggestions
-## for cmccabe, create a pull request here: https://tildegit.org/cmccabe/TerminalTrain
-## or email cmccabe at cmccabe@rawtext.club
-##
-## -----------------
-##
-## WHAT IS IT?
-## like sl (the ls typo prank), but each car on the train is a x*y character ascii art
-## produced by tilde.town.
-##
-## ( original sl source code of sl?   https://github.com/mtoyoda/sl )
-##
-## TODO:
-##       * loosen the restriction on allowable characters in train cars.  right now, limited
-##         to characters in python's string.printable list.
-##       * turn main loop into a function, so cmd line arg reader can call it (with -p) and quit.
-##       * figure out why tilde.train doesn't work in some terminals (sthg sthg unicode...)
-##       * BUGFIX-1 - something about inclusion default cars adding extra "links" to the train.
-##       * the -p (print train) option should print all cars, not limited to the max_cars value. 
-##       * related to BUGFIX-1, that seems to impact spacers (links) between cars.
-##       * allow users to create multiple frames so their cars can be animated (difficulty=med+)
-##       * allow user configurable speed and number of train cars
-##       * allow users to move the train up or down with arrow keys
-##         -- worked with asciimatics, but python curses blocks on getch()
-##
+#  _   _ _    _      _            _
+# | |_(_) |__| |___ | |_ _ _ __ _(_)_ _
+# |  _| | / _` / -_)|  _| '_/ _` | | ' \
+# \__|_|_\__,_\___(_)__|_| \__,_|_|_||_|
+#
+# tilde.train is an instance of TerminalTrain.  It was originally developed
+# by cmccabe on tilde.town (https://tildegit.org/cmccabe/TerminalTrain) but is now
+# maintained by vilmibm.
+#
+# If you want to contribute code improvements, create a pull request here:
+# https://git.tilde.town/vilmibm/tilde-train
+#
+# -----------------
+#
+# WHAT IS IT?
+# like sl (the ls typo prank), but each car on the train is a x*y character ascii art
+# produced by tilde.town.
+#
+# ( original sl source code of sl?   https://github.com/mtoyoda/sl )
+#
+# TODO:
+#       * loosen the restriction on allowable characters in train cars.  right now, limited
+#         to characters in python's string.printable list.
+#       * turn main loop into a function, so cmd line arg reader can call it (with -p) and quit.
+#       * figure out why tilde.train doesn't work in some terminals (sthg sthg unicode...)
+#       * BUGFIX-1 - something about inclusion default cars adding extra "links" to the train.
+#       * the -p (print train) option should print all cars, not limited to the max_cars value.
+#       * related to BUGFIX-1, that seems to impact spacers (links) between cars.
+#       * allow users to create multiple frames so their cars can be animated (difficulty=med+)
+#       * allow user configurable speed and number of train cars
+#       * allow users to move the train up or down with arrow keys
+#         -- worked with asciimatics, but python curses blocks on getch()
+#
 
-from random import shuffle ## allowing us to randomize selection of cars.
-import glob  ## allowing us to search the file system for .choochoo files.
-import sys ## so we can read command line arguments.
-import getpass ## so we can get the user's username
+from random import shuffle # allowing us to randomize selection of cars.
+import glob  # allowing us to search the file system for .choochoo files.
+import sys # so we can read command line arguments.
 import curses
 from signal import signal, SIGINT
-import time ## allowing the loop steps of train animation to be slowed
-import string ## for input validation
+import time # allowing the loop steps of train animation to be slowed
+import string # for input validation
+from html import escape
+from inspect import cleandoc
+from pathlib import Path
 
 traincarFN = ".choochoo"
-max_x = 35  ## max length of train car.
-max_y = 10  ## max height of train car.
-max_cars = 10 ## most cars to include in one train.
-print_train = False ## print train to file (instead of the screen scroll)
+max_x = 35  # max length of train car.
+max_y = 10  # max height of train car.
+max_cars = 10 # most cars to include in one train.
+print_train = False # print train to file (instead of the screen scroll)
 
-train = [""]*max_y ## empty train of correct height.
-cars = []
+train = [""]*max_y # empty train of correct height.
+cars: list[list[str]] = []
 
-engine = """        ____                      
-       |____|         ------------
-        |  |  ===     |  ------  |
-     ___|  |__| |_____| |   O  | |
-    |  |              | |__/V\_| |
-   [[  |                         |
-    |  | ------------ |   ~town  |
-    |__|______________|__________|
- //// / _\__/__\__/__\      /  \  
-////  \__/  \__/  \__/      \__/  """
-engine = engine.split("\n")
+engine = [
+  r"        ____                      ",
+  r"       |____|         ------------",
+  r"        |  |  ===     |  ------  |",
+  r"     ___|  |__| |_____| |   O  | |",
+  r"    |  |              | |__/V\_| |",
+  r"   [[  |                         |",
+  r"    |  | ------------ |   ~town  |",
+  r"    |__|______________|__________|",
+  r" //// / _\__/__\__/__\      /  \  ",
+  r"////  \__/  \__/  \__/      \__/  ",
+]
 
-caboose = """                        ||        
-         =============  ||        
-=========|           |==========  
-  |    ----          ----     |   
-  |   |    |        |    |    |   
-  |    ----          ----     |   
-  |    tilde.town railways    |   
-==|                           |== 
-== - /  \-/  \-----/  \-/  \ - == 
-     \__/ \__/     \__/ \__/      """
-caboose = caboose.split("\n")
+caboose = [
+  r"                        ||        ",
+  r"         =============  ||        ",
+  r"=========|           |==========  ",
+  r"  |    ----          ----     |   ",
+  r"  |   |    |        |    |    |   ",
+  r"  |    ----          ----     |   ",
+  r"  |    tilde.town railways    |   ",
+  r"==|                           |== ",
+  r"== - /  \-/  \-----/  \-/  \ - == ",
+  r"     \__/ \__/     \__/ \__/      ",
+]
 
-default_car = """ ----------------------------  
-|                            |
-|    YOUR TRAIN CAR HERE!    |  
-|       Just create a        |  
-|      ~/.choochoo file!     |
-|   __   __        __   __   |
- - /  \-/  \------/  \-/  \ -
-   \__/ \__/      \__/ \__/"""
-default_car = default_car.split("\n")
+default_car = [
+  r" ---------------------------- ",
+  r"|                            |",
+  r"|    YOUR TRAIN CAR HERE!    |",
+  r"|       Just create a        |",
+  r"|      ~/.choochoo file!     |",
+  r"|   __   __        __   __   |",
+  r" - /  \-/  \------/  \-/  \ - ",
+  r"   \__/ \__/      \__/ \__/   ",
+]
 
+class CarError(Exception):
+  """Error related validating a car."""
 
 def print_help():
-  print("")
-  print("~ ~ Hooray! You've found the tilde.train! ~ ~")
-  print("")
-  print("To add your own car to a future train, create")
-  print("a .choochoo file in your home directory and")
-  print("make sure it is 'other' readable, for example:")
-  print("")
-  print("                         chmod 644 ~/.choochoo")
-  print("")
-  print("The file should contain an ascii drawing of a")
-  print("train car no more than " + str(max_x) + " characters wide")
-  print("and " + str(max_y) + " characters tall.")
-  print("")
-  print("Only printable ascii characters are accepted for now.")
-  print("Run the command again followed by a -t switch to test")
-  print("your .choochoo file and report any non accepted chars.")
-  print("")
-  print("Each train contains a random selection of cars")
-  print("from across tilde.town user home directories.")
-  print("Don't worry, yours will be coming around the")
-  print("bend soon!")
-  print("")
-  print("~ ~                 ~ ~                   ~ ~")
-  print("")
+  print(
+    cleandoc(
+      f"""
+      ~ ~ Hooray! You've found the tilde.train! ~ ~
+
+      To add your own car to a future train, create
+      a .choochoo file in your home directory and
+      make sure it is 'other' readable, for example:
+
+        chmod 644 ~/.choochoo
+
+      The file should contain an ascii drawing of a
+      train car no more than {max_x} characters wide
+      and {max_y} characters tall.
+
+      Only printable ascii characters are accepted for now.
+      Run the command again followed by a -t switch to test
+      your .choochoo file and report any non accepted chars.
+
+      Each train contains a random selection of cars
+      from across tilde.town user home directories.
+      Don't worry, yours will be coming around the
+      bend soon!
+
+      ~ ~                 ~ ~                   ~ ~
+      """
+    )
+  )
 
 
 def test_user_car():
-  username = getpass.getuser()
-  fname = "/home/" + username + "/" + traincarFN
+  fname = Path.home() / traincarFN
   try:
-    myfile =  open(fname, 'r')
-  except:
-    print("ERROR: Couldn't open " + fname)
-    print("Either it doesn't exist, or is not readble by the tilde.train script.")
-    exit()
+    choochoo_string = fname.read_text("utf-8")
+  except OSError as err:
+    raise OSError(
+      f"Couldn't open {fname}\n"
+      "Either it doesn't exist, or is not readble by the tilde.train script."
+    ) from err
 
-  choochoo_string = myfile.read()
   choochoo_list = choochoo_string.split("\n")
 
   car = "\n".join(choochoo_list)
-  car2 = car.replace("\t", "") ## do not allow tabs
-  car2 = car2.replace("\v", "") ## do not allow vertical tabs
-  car2 = car2.replace("\f", "") ## do not allow line feeds
-  car2 = car2.replace("\r", "") ## do not allow carriage returns
+  car2 = car.replace("\t", "") # do not allow tabs
+  car2 = car2.replace("\v", "") # do not allow vertical tabs
+  car2 = car2.replace("\f", "") # do not allow line feeds
+  car2 = car2.replace("\r", "") # do not allow carriage returns
   car2 = ''.join([i if string.printable.find(i) >= 0 else ' ' for i in car2])
 
   print("")
@@ -160,10 +169,7 @@ def test_user_car():
     print(string.printable.strip())
     print("")
     print("Yours contained " + bad_chars)
-    exit()
-
-#  print("")
-#  print("Test results:")
+    sys.exit(1)
 
   train_height = len(choochoo_list)
   train_length = len(max(choochoo_list, key=len))
@@ -171,90 +177,85 @@ def test_user_car():
   if train_height > max_y+1:
     print("FAIL. Your train car is too tall.")
     print("It should be no taller than " + str(max_y) + " lines in height.")
-    myfile.close()
-    exit()
+    sys.exit(1)
 
   if train_length > max_x:
     print("FAIL. Your train car is too long.")
     print("It should be no longer than " + str(max_x) + " characters in length.")
-    myfile.close()
-    exit()
+    sys.exit(1)
 
   print("PASS. Your train car will work on the tilde.town tracks! :)")
-  myfile.close()
-  exit()
+  sys.exit()
 
-def link_car(car):
+def link_car(car: list[str]):
   for idx,row in enumerate(car):
     car[idx] = " " + row
   car[len(car)-3] = "+" + car[len(car)-3][1:]
   car[len(car)-2] = "+" + car[len(car)-2][1:]
   return car
 
-def validate_car(car):
-## this function (1) checks that a train car isn't too tall or too long
-## (2) pads it vertically or on the right side if it is too short or if
-## not all lines are the same length and (3) removes bad characters.
+def validate_car(car: list[str]):
+# this function (1) checks that a train car isn't too tall or too long
+# (2) pads it vertically or on the right side if it is too short or if
+# not all lines are the same length and (3) removes bad characters.
 
-  car = "\n".join(car)
-  car = ''.join([i if ord(i) < 128 else ' ' for i in car])
-  car = car.split("\n")
+  car_str = "\n".join(car)
+  car_str = ''.join([i if ord(i) < 128 else ' ' for i in car_str])
+  car_list = car_str.split("\n")
 
-  ## remove blank lines from top and bottom of car,
-  ## so we can estimate its true size.
-  while car[0].strip() == "":
-    car.pop(0) ## clear top
-  while car[(len(car)-1)].strip() == "":
-    car.pop() ## clear bottom
+  # remove blank lines from top and bottom of car,
+  # so we can estimate its true size.
+  while car_list[0].strip() == "":
+    car_list.pop(0) # clear top
+  while car_list[(len(car_list)-1)].strip() == "":
+    car_list.pop() # clear bottom
 
-  ## len(choochoo_list) is the height of the train car, in number of rows.
-  if len(car) > max_y+1 or len(car) == 0:
-    return 0  ## train car too tall or non-existant; skip it.
+  # len(car_list) is the height of the train car, in number of rows.
+  if len(car_list) > max_y+1:
+    raise CarError(f"Car is too tall ({len(car_list)} > {max_y + 1}).")
+  if len(car_list) == 0:
+    raise CarError(f"Car is empty.")
 
-  ## vertically pad short cars with 1 space (lines will be lengthened later).
-  while len(car) < max_y:
-    car = [" "] + car
+  # vertically pad short cars with 1 space (lines will be lengthened later).
+  while len(car_list) < max_y:
+    car_list = [" "] + car_list
 
-  for idx,row in enumerate(car):
-    car[idx] = row.rstrip()
+  for idx,row in enumerate(car_list):
+    car_list[idx] = row.rstrip()
 
-  longest_line = len(max(car, key=len)) ## longest line in .choochoo file.
+  longest_line = len(max(car_list, key=len)) # longest line in .choochoo file.
 
-  for idx,row in enumerate(car):
-    if len(row) > max_x+1: ## check length of each row in .choochoo file.
-      return 0 ## train car too long; skip it.
+  for idx,row in enumerate(car_list):
+    if len(row) > max_x+1: # check length of each row in .choochoo file.
+      raise CarError(f"Car is too wide ({len(row)} > {max_x + 1}).")
     elif "\t" in row or "\v" in row or "\f" in row or "\r" in row:
-      return 0 # skip if contains tabs, vert tabs, line feeds or carriage ret
+      raise CarError(f"Car contains illegal control characters.")
     elif len(row) < longest_line:
       padding = " "*(longest_line - len(row))
-      car[idx] += padding ## add padding spaces.
+      car_list[idx] += padding # add padding spaces.
 
-  return car
+  return car_list
 
 
 def print_all_cars():
   for fname in glob.glob('/home/*/' + traincarFN):
     try:
       with open(fname, 'r') as myfile:
-        ## print fname ## debug, print file path and name
         choochoo_string = myfile.read()
         choochoo_list = choochoo_string.split("\n")
       if len(choochoo_list) > max_y+1:
-        continue ## the train car was too tall; skip it.
-  
-      car = validate_car(choochoo_list) ## printing is only a DEBUG feature.
-      if car != 0:
-        print("")
-        print(fname + ":")
-        print("\n".join(car)) ## print the car to stdout
-  
-      ## HOW TO CLOSE THE FILE HANDLE? fname.close(), close(fname), ...?
+        continue # the train car was too tall; skip it.
+
+      car = validate_car(choochoo_list) # printing is only a DEBUG feature.
+      print("")
+      print(fname + ":")
+      print("\n".join(car)) # print the car to stdout
+
     except:
-      pass;
-#      print "Cannot open " + fname # for debuggering purposes
+      pass
 
 
-def chuggachugga(stdscr):
+def chuggachugga(stdscr: curses.window):
   curses.curs_set(0)
   h, w = stdscr.getmaxyx()
   x_pos = w-1
@@ -262,82 +263,61 @@ def chuggachugga(stdscr):
 
   while True:
     for idx,train_layer in enumerate(reversed(train)):
-#      screen.print_at(train_layer, x_pos, (y_pos-idx))
-#      stdscr.addstr((y_pos-idx),x_pos,train_layer)
 
       train_snip_start = 0 if (x_pos >= 0) else min(abs(x_pos), len(train_layer))
       train_snip_end = w-x_pos if (w-x_pos <= len(train_layer)) else len(train_layer)
-#      train_snip_end = min(len(train_layer),w-x_pos)
       x = max(0, x_pos)
-#      stdscr.addstr(2,2,"start: " + str(train_snip_start))
-#      stdscr.addstr(3,2,"end: "+ str(train_snip_end))
-#      stdscr.addstr(4,2,"x_pos: " + str(x_pos))
-#      stdscr.addstr(5,2,"train len: " + str(len(train_layer)))
       stdscr.addstr((y_pos-idx),x,train_layer[train_snip_start:train_snip_end])
 
     x_pos -= 1
     if x_pos == -train_len:
-#      stdscr.addstr(2,5,"here we are!")
-#      time.sleep(10)
       return
 
     stdscr.refresh()
     time.sleep(.03)
 
-#    ev = stdscr.getch() ## seems like curses waits for input, which won't work here.
-#    if ev in (ord('Q'), ord('q')):
-#      return
-#    elif ev == curses.KEY_UP: ## up
-#      y_pos += 1
-#    elif ev == curses.KEY_DOWN: ## down
-#      y_pos -= 1
-
-
 def handler(signal_received, frame):
   print("Oops. The train broke.  The engineer is looking into it!")
   print("(Note: the train does not work in all terminals yet.)")
-  exit(0)
+  sys.exit(1)
 
 default_car = validate_car(default_car)
 
 if len(sys.argv) == 2 and ("-h" in sys.argv[1] or "help" in sys.argv[1]):
   print_help()
-  quit()
+  sys.exit()
 
 if len(sys.argv) == 2 and ("-t" in sys.argv[1] or "test" in sys.argv[1]):
   test_user_car()
-  quit()
+  sys.exit()
 
 if len(sys.argv) == 2 and ("-p" in sys.argv[1] or "print" in sys.argv[1]):
   print_train = True
 
 if len(sys.argv) == 2 and ("-a" in sys.argv[1] or "all" in sys.argv[1]):
   print_all_cars()
-  quit()
+  sys.exit()
 
 
-## start a loop that collects all .choochoo files and processes on in each loop
+# start a loop that collects all .choochoo files and processes on in each loop
 for fname in glob.glob('/home/*/' + traincarFN):
   car_len = 1
   try:
     with open(fname, 'r') as myfile:
-      ## print fname ## debug, print file path and name
+      # print fname # debug, print file path and name
       choochoo_string = myfile.read()
       choochoo_list = choochoo_string.split("\n")
     if len(choochoo_list) > max_y+1:
-      continue ## the train car was too tall; skip it.
+      continue # the train car was too tall; skip it.
 
-    car = validate_car(choochoo_list) ## printing is only a DEBUG feature.
-    if car != 0:
-      cars.append(car) ## start a list of lists (list of cars) here.
+    car = validate_car(choochoo_list) # printing is only a DEBUG feature.
+    cars.append(car) # start a list of lists (list of cars) here.
 
-    ## HOW TO CLOSE THE FILE HANDLE? fname.close(), close(fname), ...?
   except:
-    pass;
-    ##print "Cannot open " + fname # for debuggering purposes
+    pass
 
 while len(cars) < max_cars:
-  cars.append(default_car) ## add default cars if train too short
+  cars.append([*default_car]) # add copies of default cars if train too short
 
 shuffle(cars)
 cars = cars[0:max_cars]
@@ -360,14 +340,22 @@ train_str = "\n".join(train)
 
 if print_train:
   print("<pre>")
-  print(train_str)
+  print(escape(train_str))
   print("</pre>")
-  quit()
+  sys.exit()
 
 pad_str = " "*train_len
 train.insert(0,pad_str)
 train.append(pad_str)
 
 if __name__ == "__main__":
-  signal(SIGINT, handler)
-  curses.wrapper(chuggachugga)
+    signal(SIGINT, handler)
+    try:
+      curses.wrapper(chuggachugga)
+    except curses.error as err:
+      print(
+        f"{err}\n"
+        "Couldn't print the train for some reason. "
+        "Maybe your terminal window is too short?"
+      )
+      sys.exit(1)