diff --git a/days/input/day12_input b/days/input/day12_input
new file mode 100644
index 0000000..a302737
--- /dev/null
+++ b/days/input/day12_input
@@ -0,0 +1,4 @@
+<x=14, y=2, z=8>
+<x=7, y=4, z=10>
+<x=1, y=17, z=16>
+<x=-4, y=-1, z=1>
\ No newline at end of file
diff --git a/days/test_day12.py b/days/test_day12.py
new file mode 100644
index 0000000..3ca6e40
--- /dev/null
+++ b/days/test_day12.py
@@ -0,0 +1,34 @@
+from itertools import permutations
+import os
+import re
+
+inputfile = os.path.join(os.path.dirname(__file__), "input/day12_input")
+
+
+def get_moons():
+    with open(inputfile) as fp:
+        return [[int(m[1]), int(m[2]), int(m[3])]
+                for m in
+                re.finditer(r'x=(-?\d+).*y=(-?\d+).*z=(-?\d+)', fp.read())]
+
+
+def test_day12a():
+    moons = [(m, [0, 0, 0]) for m in get_moons()]
+    e = 0
+    for _ in range(1000):
+        for me, other in permutations(moons, 2):
+            v = me[1]
+            pa = me[0]
+            pb = other[0]
+            v[0] += -1 if pa[0] > pb[0] else 1 if pa[0] < pb[0] else 0
+            v[1] += -1 if pa[1] > pb[1] else 1 if pa[1] < pb[1] else 0
+            v[2] += -1 if pa[2] > pb[2] else 1 if pa[2] < pb[2] else 0
+        for moon in moons:
+            moon[0][0] += moon[1][0]
+            moon[0][1] += moon[1][1]
+            moon[0][2] += moon[1][2]
+
+    for p, v in moons:
+        e += (abs(p[0])+abs(p[1])+abs(p[2]))*(abs(v[0])+abs(v[1])+abs(v[2]))
+
+    assert e == 9139