diff --git a/main.py b/main.py
new file mode 100755
index 0000000..2e80ba8
--- /dev/null
+++ b/main.py
@@ -0,0 +1,139 @@
+#!/usr/bin/env python3
+
+from greenery import fsm, lego
+
+# alphabet list
+# also used as lookup table for number-strings
+n = [str(x) for x in range(10)]
+
+# start and end states
+s, e = "S", "E"
+
+# get the state name for a position and the current mod-sum
+def p(p, n):
+	if	p == 0:
+		return s
+	return str(p) + ":" + str(n)
+
+# list of all states
+states = [p(x, y) for x in range(1, 16) for y in range(10)] + [s, e]
+
+# this function handles the odd number case for Luhn's algorithm
+def modi(p, n):
+	if p % 2 == 0:
+		if n > 4:
+			return n * 2 - 9
+		else:
+			return n * 2
+	else:
+		return n
+
+# generate all state transitions to non-final states
+# t is the transition dictionary
+#   the keys are the current states
+#   the values are dictionaries from the input alphabet
+#   value to the next state
+t = {}
+for _p in range(15):
+	for n1 in range(10):
+		# _p == 0 is the initial state -> n1 is always 0
+		if _p == 0 and n1 > 0:
+			continue
+
+		t[p(_p, n1)] = {}
+		for n2 in range(10):
+			# checks for mastercard 50s range
+			if _p == 0 and n2 != 5:
+				continue
+			if _p == 1 and (n2 == 0 or n2 > 5):
+				continue
+
+			t[p(_p, n1)][n[n2]] = p(_p + 1, (n1 + modi(_p, n2)) % 10)
+
+# generate transitions to the final state
+for n1 in range(10):
+	t[p(15, n1)] = {}
+	for n2 in range(10):
+		if (n1 + modi(15, n2)) % 10 == 0:
+			t[p(15, n1)][n[n2]] = e
+
+# build FSM from alphabet, state set and state transitions
+machine = fsm.fsm(
+	alphabet = set(n),
+	states   = set(states),
+	initial  = s,
+	finals   = {e},
+	map      = t,
+)
+
+# hashtag #datadriven tests
+tests = [
+	# generated valid (https://fake-name-generator.com/Fake-MasterCard-Number-Generator)
+	("5222084305213022", True),
+	("5223625675778488", True),
+	("5306937024627310", True),
+	("5406251442761555", True),
+	("5216055885117468", True),
+	("5197252600542111", True),
+	("5549661903610174", True),
+	
+	("6216055885117468", False), # Luhn check fail
+	("5316055885117468", False),
+	("5226055885117468", False),
+	("5217055885117468", False),
+	("5216155885117468", False),
+	("5216065885117468", False),
+	("5216054885117468", False),
+	("5216055985117468", False),
+	("5216055875117468", False),
+	("5216055886117468", False),
+	("5216055885217468", False),
+	("5216055885107468", False),
+	("5216055885118468", False),
+	("5216055885117568", False),
+	("5216055885117478", False),
+	("5216055885117469", False),
+	("4356180747362517", False), # Visa, not Mastercard
+]
+
+# Luhn's check for test cases to confirm if they were generated correctly
+# only works for mastercard numbers (the visa test will case fail here)
+if False:
+	for n, r in tests:
+		s = 0
+		for i, c in enumerate(n):
+			s += modi(i, int(c))
+		if not (r == (s % 10 == 0)):
+			print("test case %s (%s) is invalid: checksum %d" % (n, r, s % 10))
+			exit(1)
+
+print("Original FSM:")
+print(machine)
+print()
+
+print("Reducing...")
+machine = machine.reduce()
+
+print("Reduced FSM:")
+print(machine)
+print()
+
+print("Testing:")
+overall = True
+for n, r in tests:
+	print("Test case %s (%s)" % (n, r))
+	if r == machine.accepts(n):
+		print("  OK!")
+	else:
+		print("  FAIL!")
+		overall = False
+print()
+
+if not overall:
+	print("Test suite failed!")
+	exit(1)
+
+print("Building regex...")
+rex = lego.from_fsm(machine)
+print()
+print(rex)