diff --git a/2019/aoc2019/day16.py b/2019/aoc2019/day16.py
index 217fe68..e61987e 100644
--- a/2019/aoc2019/day16.py
+++ b/2019/aoc2019/day16.py
@@ -27,7 +27,31 @@ def simulate(numbers: List[int]) -> str:
     return ''.join(str(s) for s in numbers[:8])
 
 
+def simulate2(numbers: List[int]) -> str:
+    numbers = numpy.tile(numpy.array(numbers, dtype=numpy.int), 10000)
+    starting_index = 0
+
+    for n in numbers[:7]:
+        starting_index *= 10
+        starting_index += n
+
+    assert starting_index > len(numbers) / 2
+
+    numbers = numbers[starting_index:]
+
+    for _ in range(100):
+        numbers = numpy.abs(numpy.flip(numpy.cumsum(numpy.flip(numbers)))) % 10
+
+    return ''.join(str(s) for s in numbers[:8])
+
+
 def part1(data: TextIO) -> str:
     numbers = read_input(data)
 
     return simulate(numbers)
+
+
+def part2(data: TextIO) -> str:
+    numbers = read_input(data)
+
+    return simulate2(numbers)
diff --git a/2019/tests/day16.py b/2019/tests/day16.py
deleted file mode 100644
index f83024d..0000000
--- a/2019/tests/day16.py
+++ /dev/null
@@ -1,15 +0,0 @@
-import pytest
-
-from aoc2019.day16 import simulate
-
-
-@pytest.mark.parametrize('data,correct', [
-    ('80871224585914546619083218645595', '24176176'),
-    ('19617804207202209144916044189917', '73745418'),
-    ('69317163492948606335995924319873', '52432133'),
-])
-def test_sample_part1(data: str, correct: str):
-    numbers = [int(c) for c in data]
-
-    assert simulate(numbers) == correct
-    pass
diff --git a/2019/tests/test_day16.py b/2019/tests/test_day16.py
new file mode 100644
index 0000000..67a49db
--- /dev/null
+++ b/2019/tests/test_day16.py
@@ -0,0 +1,25 @@
+import pytest
+
+from aoc2019.day16 import simulate, simulate2
+
+
+@pytest.mark.parametrize('data,correct', [
+    ('80871224585914546619083218645595', '24176176'),
+    ('19617804207202209144916044189917', '73745418'),
+    ('69317163492948606335995924319873', '52432133'),
+])
+def test_sample_part1(data: str, correct: str):
+    numbers = [int(c) for c in data]
+
+    assert simulate(numbers) == correct
+
+
+@pytest.mark.parametrize('data,correct', [
+    ('03036732577212944063491565474664', '84462026'),
+    ('02935109699940807407585447034323', '78725270'),
+    ('03081770884921959731165446850517', '53553731'),
+])
+def test_sample_part2(data: str, correct: str):
+    numbers = [int(c) for c in data]
+
+    assert simulate2(numbers) == correct