diff --git a/harald/api.py b/harald/api.py
index 5316603..b60dd3d 100644
--- a/harald/api.py
+++ b/harald/api.py
@@ -21,7 +21,9 @@ class APIError(Exception):
 
 
 def select(problem: str):
-    response = requests.post(config.contest_url + "/select", json={"problemName": problem, "id": config.id})
+    response = requests.post(
+        config.contest_url + "/select", json={"problemName": problem, "id": config.id}
+    )
     if not response.ok:
         raise APIError(f"{response.status_code}: {response.text}")
 
@@ -43,7 +45,6 @@ def init_explore_cache():
 
 
 def write_explore_cache():
-    return
     with open("explore_cache.json", "w") as h:
         h.write(json.dumps(explore_cache))
 
diff --git a/harald/explore.py b/harald/explore.py
index 71d9874..071eca8 100755
--- a/harald/explore.py
+++ b/harald/explore.py
@@ -1,68 +1,20 @@
 #!/usr/bin/env python3
 
 import itertools
-import functools
 import json
 import os.path
 import sys
-import random
 from collections import defaultdict
 
 import api
 import graph
+from path import DOORS, Path
 
 
 class ExploreError(Exception):
     pass
 
 
-@functools.total_ordering
-class Path:
-    def __init__(self, path=""):
-        if isinstance(path, list):
-            path = "".join(str(p) for p in path)
-        self.path = path
-
-    def __repr__(self):
-        return "." + self.path if self.path else "."
-
-    def __bool__(self):
-        return bool(self.path)
-
-    def __eq__(self, other):
-        return self.path == other.path
-
-    def __lt__(self, other):
-        return (len(self.path), self.path) < (len(other.path), other.path)
-
-    def __hash__(self):
-        return self.path.__hash__()
-
-    def __format__(self, spec):
-        return str(self).__format__(spec)
-
-    def __add__(self, other):
-        return Path(self.path + other.path)
-
-    def __len__(self):
-        return len(self.path)
-
-    def __getitem__(self, idx):
-        return Path(self.path.__getitem__(idx))
-
-    def last(self):
-        return Path(self.path[:-1]), int(self.path[-1])
-
-    def shorten(self, path, pmerge):
-        if self.path.startswith(pmerge.path):
-            return Path(path.path + self.path[len(pmerge.path) :])
-        else:
-            return self
-
-
-DOORS = [Path(str(i)) for i in range(6)]
-
-
 class Explore:
     def __init__(self, problem, probes):
         self.problem = problem
@@ -104,7 +56,7 @@ class Explore:
 
         for path, presults in zip(paths, itertools.batched(results, len(probes))):
             prefix_len = len(mark) - 2 * num_marks + len(path)
-            print("id", path, results)
+            # print("id", path, results)
             self.update(path, [res[prefix_len:] for res in presults])
 
     def _add_room(self, path, results):
@@ -143,7 +95,9 @@ class Explore:
                 # self.dump()
 
                 p, rid = self.neighbors[pl][d]
-                assert rid is None or rid == room_id, f"penultimate {path} {pl}: {rid} != {room_id}"
+                assert (
+                    rid is None or rid == room_id
+                ), f"penultimate {path} {pl}: {rid} != {room_id}"
                 self.neighbors[pl][d] = (p, room_id)
 
                 # self.dump()
@@ -177,7 +131,7 @@ class Explore:
         try to unify rooms at paths p1, p2
         return unified rooms
         """
-        print("unify", path1, path2)
+        # print("unify", path1, path2)
         if path1 == path2:
             return
 
@@ -185,7 +139,9 @@ class Explore:
         assert path2 in self.rooms, f"room '{path2}' not explored"
 
         if self.rooms[path1] != self.rooms[path2]:
-            raise ExploreError(f"ids of '{path1}'({self.rooms[path1]}) and '{path2}'({self.rooms[path2]}) do not match")
+            raise ExploreError(
+                f"ids of '{path1}'({self.rooms[path1]}) and '{path2}'({self.rooms[path2]}) do not match"
+            )
 
         path = min(path1, path2)
         pmerge = max(path1, path2)
@@ -194,9 +150,13 @@ class Explore:
         self.unification_id[pmerge] = path
 
         merged_neighbors = []
-        for n, ((p, rid), (pm, rmid)) in enumerate(zip(self.neighbors[path], self.neighbors[pmerge])):
+        for n, ((p, rid), (pm, rmid)) in enumerate(
+            zip(self.neighbors[path], self.neighbors[pmerge])
+        ):
             if rid and rmid and rid != rmid:
-                raise ExploreError(f"neighbor {n} of '{path}'({rid}) and '{pmerge}'({rmid}) do not match")
+                raise ExploreError(
+                    f"neighbor {n} of '{path}'({rid}) and '{pmerge}'({rmid}) do not match"
+                )
             merged_neighbors.append((self._path(p), rid or rmid))
 
         # fix rooms
@@ -224,7 +184,9 @@ class Explore:
                 new.append((np_, rid))
                 if rid:
                     try:
-                        assert np_ in self.rooms, f"unify: path {np} {np_} of {(p, ns)} not in rooms"
+                        assert (
+                            np_ in self.rooms
+                        ), f"unify: path {np} {np_} of {(p, ns)} not in rooms"
                     except AssertionError as exc:
                         self.dump()
                         raise exc
@@ -253,7 +215,9 @@ class Explore:
             yield unexplored
 
     def is_explored(self):
-        return next(self.unexplored(), None) is None and all(len(p) == 1 for p in self.room_ids.values())
+        return next(self.unexplored(), None) is None and all(
+            len(p) == 1 for p in self.room_ids.values()
+        )
 
     def layout(self, orig=None, start=Path()):
         aedi = graph.Aedificium(self.problem)
@@ -271,12 +235,18 @@ class Explore:
             for src_door, (trg_path, _) in enumerate(ns):
                 src = (src_path, src_door)
                 trg_door = next(
-                    (j for j, (p, rid) in enumerate(self.neighbors[trg_path]) if p == src_path),
+                    (
+                        j
+                        for j, (p, rid) in enumerate(self.neighbors[trg_path])
+                        if p == src_path
+                    ),
                     None,
                 )
                 if trg_door is None:
                     # raise Exception(f"backlink not found: {(src, trg_path, self.neighbors[trg_path])}")
-                    print(f"backlink not found: {(src, trg_path, self.neighbors[trg_path])}")
+                    print(
+                        f"backlink not found: {(src, trg_path, self.neighbors[trg_path])}"
+                    )
                     connect_errors.append((src[0], src[1], trg_path))
                     trg_door = 0
                 trg = (trg_path, trg_door)
@@ -295,8 +265,14 @@ class Explore:
         if connect_errors:
             # try to fix connection issues
             updated = False
-            src = {src_path: (trg_path, src_door) for src_path, src_door, trg_path in connect_errors}
-            trg = {trg_path: (src_path, src_door) for src_path, src_door, trg_path in connect_errors}
+            src = {
+                src_path: (trg_path, src_door)
+                for src_path, src_door, trg_path in connect_errors
+            }
+            trg = {
+                trg_path: (src_path, src_door)
+                for src_path, src_door, trg_path in connect_errors
+            }
 
             for trg_path, (src_path, src_door) in trg.items():
                 if trg_path in src:
@@ -368,7 +344,9 @@ def mark_solve(problem, nrooms):
                 mark_loop = mark_loop + p + get_mark(rid, mask) + q
 
             print("marked", mark_loop, loop)
-            assert exs[-1].walk(loop) == Path(), f"loop doesn't close {exs[-1].walk(loop)}"
+            assert (
+                exs[-1].walk(loop) == Path()
+            ), f"loop doesn't close {exs[-1].walk(loop)}"
 
         ex = Explore(problem, probes)
         exs.append(ex)
@@ -391,7 +369,9 @@ def mark_solve(problem, nrooms):
 
         assert ex.is_explored(), "not fully explored"
         if nrooms % len(ex.rooms) != 0:
-            raise ExploreError(f"not all rooms could be identifed {len(ex.rooms)}/{nrooms}")
+            raise ExploreError(
+                f"not all rooms could be identifed {len(ex.rooms)}/{nrooms}"
+            )
 
         if len(ex.rooms) == nrooms:
             print("found all rooms")
@@ -445,7 +425,9 @@ if __name__ == "__main__":
     with open(os.path.join("..", "problems.json")) as h:
         problems = json.loads(h.read())
 
-        problems = {p["problem"]: {"size": p["size"], "idx": i} for i, p in enumerate(problems)}
+        problems = {
+            p["problem"]: {"size": p["size"], "idx": i} for i, p in enumerate(problems)
+        }
 
     if problem not in problems:
         raise ExploreError(f"unknown problem {problem}")
diff --git a/harald/explore.sh b/harald/explore.sh
index aaf2615..dc34e1b 100755
--- a/harald/explore.sh
+++ b/harald/explore.sh
@@ -6,13 +6,21 @@ if [ -z "$PROBLEMS" ] ; then
     PROBLEMS=$(jq -r '.[]|.problem' ../problems.json)
 fi
 
+if [ $TRIES -eq 0 ]; then
+    FOREVER=1
+    TRIES=1
+fi
+
 TRIES=${TRIES:-10}
 
-for problem in $PROBLEMS; do
-    for t in $(seq $TRIES); do
-        ./explore.py $problem
-        if [ $? -eq 0 ]; then
-            break
-        fi
-    done 
+while : ; do
+    for problem in $PROBLEMS; do
+        for t in $(seq $TRIES); do
+            ./explore.py $problem
+            if [ $? -eq 0 ]; then
+                break
+            fi
+        done 
+    done
+    [ -n "$FOREVER" ] || break
 done
diff --git a/harald/graph.py b/harald/graph.py
index 1ed117e..84d68de 100644
--- a/harald/graph.py
+++ b/harald/graph.py
@@ -12,7 +12,9 @@ class Aedificium:
 
     def add_edge(self, scr, src_d, trg, trg_d):
         self.graph.add_edge(
-            pydot.Edge(scr, trg)  # , headport=self.PORTS[src_d], tailport=self.PORTS[trg_d])
+            pydot.Edge(
+                scr, trg
+            )  # , headport=self.PORTS[src_d], tailport=self.PORTS[trg_d])
         )
 
     def render(self):
diff --git a/harald/path.py b/harald/path.py
new file mode 100644
index 0000000..d4e9f4e
--- /dev/null
+++ b/harald/path.py
@@ -0,0 +1,48 @@
+import functools
+
+
+@functools.total_ordering
+class Path:
+    def __init__(self, path=""):
+        if isinstance(path, list):
+            path = "".join(str(p) for p in path)
+        self.path = path
+
+    def __repr__(self):
+        return "." + self.path if self.path else "."
+
+    def __bool__(self):
+        return bool(self.path)
+
+    def __eq__(self, other):
+        return self.path == other.path
+
+    def __lt__(self, other):
+        return (len(self.path), self.path) < (len(other.path), other.path)
+
+    def __hash__(self):
+        return self.path.__hash__()
+
+    def __format__(self, spec):
+        return str(self).__format__(spec)
+
+    def __add__(self, other):
+        return Path(self.path + other.path)
+
+    def __len__(self):
+        return len(self.path)
+
+    def __getitem__(self, idx):
+        return Path(self.path.__getitem__(idx))
+
+    def last(self):
+        return Path(self.path[:-1]), int(self.path[-1])
+
+    def shorten(self, path, pmerge):
+        if self.path.startswith(pmerge.path):
+            return Path(path.path + self.path[len(pmerge.path) :])
+        else:
+            return self
+
+
+DOORS = [Path(str(i)) for i in range(6)]