diff --git a/day15.py b/day15.py
new file mode 100644
index 0000000..53c7aee
--- /dev/null
+++ b/day15.py
@@ -0,0 +1,129 @@
+from intcode import Interpreter, WaitForInput
+
+NORTH = 1
+SOUTH = 2
+WEST  = 3
+EAST  = 4
+
+DIRS = [NORTH, SOUTH, EAST, WEST]
+
+OPPOSITE = {NORTH : SOUTH,
+            SOUTH : NORTH,
+            EAST  : WEST,
+            WEST  : EAST
+           }
+
+WALL  = 0
+EMPTY = 1
+OXY   = 2
+
+ENCODING = {WALL  : '#',
+            EMPTY : '.',
+            OXY   : 'O'
+           }
+
+def move(pos, dir):
+    if dir == NORTH:
+        return pos[0], pos[1] + 1
+    if dir == SOUTH:
+        return pos[0], pos[1] - 1
+    if dir == EAST:
+        return pos[0] + 1, pos[1]
+    if dir == WEST:
+        return pos[0] - 1, pos[1]
+    return NotImplemented
+
+class DroidIO:
+    def __init__(self):
+        self._input = None
+        self._output = None
+
+    def pop_input(self):
+        i = self._input
+        if i == None:
+            raise WaitForInput
+        self._input = None
+        return i
+
+    def append_output(self, x):
+        self._output = x
+
+    def flush(self):
+        o = self._output
+        self._output = None
+        return o
+
+    def write(self, x):
+        self._input = x
+
+class Droid(Interpreter):
+    def __init__(self, program):
+        super().__init__(program, DroidIO)
+        self.pos = 0, 0
+
+    def move(self, dir):
+        out = self.eval(dir)
+        if out != WALL:
+            self.pos = move(self.pos, dir)
+        return out 
+
+
+class Map(dict):
+    def __init__(self, encoding):
+        super().__init__()
+        self.encoding = encoding
+
+    def __str__(self):
+        xs, ys = tuple(zip(*self.keys()))
+        r = str()
+        for y in range(min(ys), max(ys)+1):
+            for x in range(min(xs), max(xs)+1):
+                if x == y == 0:
+                    r += 'X'
+                elif (x, y) not in self:
+                    r += ' '
+                else:
+                    r += self.encoding[self[(x, y)]]
+            r += '\n'
+        return r
+
+def map_space(droid, map=None):
+    if map == None:
+        map = Map(ENCODING)
+    for dir in DIRS:
+        new_pos = move(droid.pos, dir)
+        if new_pos in map:
+            continue
+        object = droid.move(dir)
+        map[new_pos] = object
+        if object == WALL:
+            continue
+        map_space(droid, map)
+        droid.move(OPPOSITE[dir])
+    return map
+
+def shortest_paths(map, pos, visited=None):
+    if visited == None:
+        visited = {pos : 0}
+    path = visited[pos] + 1
+    for dir in DIRS:
+        new = move(pos, dir)
+        if map[new] == WALL or (new in visited and visited[new] <= path):
+            continue
+        visited[new] = path
+        shortest_paths(map, new, visited)
+    return visited
+
+def preproc(puzzle_input):
+    program = list(map(int, puzzle_input.split(',')))
+    droid = Droid(program)
+    area_map = map_space(droid)
+    x, y = tuple(filter(lambda x: x[1]==OXY, area_map.items()))[0][0]
+    path_map = shortest_paths(area_map, (x, y))
+    return path_map
+
+def partI(path_map):
+    return path_map[(0, 0)]
+
+def partII(path_map):
+    return max(path_map.values())