diff --git a/lib/__init__.py b/lib/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/lib/causal.py b/lib/causal.py
new file mode 100644
index 0000000..847e30f
--- /dev/null
+++ b/lib/causal.py
@@ -0,0 +1,90 @@
+import sys
+
+if sys.version_info[0] < 3:
+    raise "Must be using Python 3"
+
+class Causal:
+    def __init__(self, causalcode=""):
+        self.causalcode = causalcode
+        self._description = ""
+        self._title = ""
+        self._prechac = ""
+        self._sequence = ""
+        self._fourhanded = ""
+
+    # https://docs.python.org/3/library/functions.html#property
+
+    @property
+    def description(self):
+        return self._description
+
+    @description.setter
+    def description(self, value):
+        self._description = value
+
+    @property
+    def title(self):
+        return self._title
+
+    @title.setter
+    def title(self, value):
+        self._title = value
+
+    @property
+    def prechac(self):
+        return self._prechac
+
+    @prechac.setter
+    def prechac(self, value):
+        self._prechac = value
+
+    @property
+    def sequence(self):
+        return self._sequence
+
+    @sequence.setter
+    def sequence(self, value):
+        self._sequence = value
+
+    @property
+    def fourhanded(self):
+        return self._fourhanded
+
+    @fourhanded.setter
+    def fourhanded(self, value):
+        if self.isvalid_fourhanded(value):
+            self._fourhanded = str(value)
+        else:
+            raise Exception("Can't parse as fourhanded siteswap")
+        # convert to prechac and fill prechac value
+
+    def isvalid_fourhanded(self, value):
+        if type(value) == int:
+            value = str(value)
+        elif type(value) == str:
+            if value.isdigit():
+                next
+            else:
+                return False
+        else:
+            return False
+
+        # inspired by https://icculus.org/jugglemaster/docs/validate.txt
+        lst = [1] * len(value)
+        for i, c in enumerate(value):
+            j = ( i + int(c) ) % len(value)
+            lst[j] = lst[j] - 1
+        for i in lst:
+            if i != 0:
+                return False
+        return True
+
+    def fourhanded_to_local(self, value):
+        # local notation from https://jonglieren-jena.de/ppa/anthology.pdf
+        # This is the local siteswap of the pattern accompanying a global siteswap. Subscripts
+        # indicate the starting positions of the different jugglers. So than in
+        # A7B65 the juggler A starts with a 7 while B starts with a 6
+
+        if not self.isvalid_fourhanded(value):
+            raise Exception("Can't parse as fourhanded siteswap")
+        return
diff --git a/test/__init__.py b/test/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/test/test_causal.py b/test/test_causal.py
new file mode 100644
index 0000000..281115a
--- /dev/null
+++ b/test/test_causal.py
@@ -0,0 +1,72 @@
+import unittest
+import sys
+import os.path
+sys.path.append(os.path.join(os.path.dirname(__file__), '..'))
+
+if sys.version_info[0] < 3:
+    raise "Must be using Python 3"
+
+from lib.causal import Causal
+
+# The main methods that we make use of in unit testing for Python are:
+#
+# assert: base assert allowing you to write your own assertions
+# assertEqual(a, b): check a and b are equal
+# assertNotEqual(a, b): check a and b are not equal
+# assertIn(a, b): check that a is in the item b
+# assertNotIn(a, b): check that a is not in the item b
+# assertFalse(a): check that the value of a is False
+# assertTrue(a): check the value of a is True
+# assertIsInstance(a, TYPE): check that a is of type "TYPE"
+# assertRaises(ERROR, a, args): check that when a is called with args that it raises ERROR
+#
+# There are more methods available to us, which you can view - see
+# https://docs.python.org/2/library/unittest.html
+
+
+class TestCausal(unittest.TestCase):
+    def setUp(self):
+        self.causal = Causal()
+
+    def test_init(self):
+        causal = Causal()
+        self.assertIsInstance(causal, Causal)
+
+    def test_description_properties(self):
+        self.causal.description = "blaat"
+        self.assertEqual(self.causal.description, "blaat")
+
+    def test_title_properties(self):
+        self.causal.title = "blaat"
+        self.assertEqual(self.causal.title, "blaat")
+
+    def test_prechac_properties(self):
+        self.causal.prechac = "blaat"
+        self.assertEqual(self.causal.prechac, "blaat")
+
+    def test_sequence_properties(self):
+        self.causal.sequence = "blaat"
+        self.assertEqual(self.causal.sequence, "blaat")
+
+    def test_fourhanded_properties(self):
+        self.causal.fourhanded = "7746666"
+        self.assertEqual(self.causal.fourhanded, "7746666")
+        self.assertRaises(Exception, self.causal.fourhanded, "blaat")
+        self.assertRaises(Exception, self.causal.fourhanded, 8.5)
+        self.assertRaises(Exception, self.causal.fourhanded, "7746666")
+
+    def test_isvalid_fourhanded(self):
+        self.assertEqual(self.causal.isvalid_fourhanded(7746666), True) # Jim's three count
+        self.assertEqual(self.causal.isvalid_fourhanded("7746666"), True) # Jim's three count
+        self.assertEqual(self.causal.isvalid_fourhanded("8746666"), False)
+        self.assertEqual(self.causal.isvalid_fourhanded("blaat"), False)
+        self.assertEqual(self.causal.isvalid_fourhanded(8.5), False)
+
+    def test_fourhanded_to_local(self):
+        self.assertRaises(Exception, self.causal.fourhanded_to_local, "blaat")
+        self.assertEqual(self.causal.fourhanded_to_local(7746666), "[A]7466[B]766") # Jim's three count
+        self.assertEqual(self.causal.fourhanded_to_local(772626), "[A]722/[B]766") # "Skip" 5c pzz/pss
+        self.assertEqual(self.causal.fourhanded_to_local(777726), "[A]772/[B]776") # "Jonix" 6c ppz/pps
+
+if __name__ == '__main__':
+    unittest.main()