diff --git a/engine.py b/engine.py
index 3c4dcdf..0f811d9 100755
--- a/engine.py
+++ b/engine.py
@@ -7,8 +7,11 @@ BRANDS: dict[str, str] = {
     "greggs": "[\"brand:wikidata\"=\"Q3403981\"]",
 }
 
+EncodedLocation = list[float, list[float]]
+
 
 def fetch_data(brand: str) -> list[tuple[float | None, float | None]]:
+    """Fetch a list of locations from OSM."""
     api = overpy.Overpass()
 
     filters = BRANDS[brand]
@@ -29,7 +32,22 @@ def fetch_data(brand: str) -> list[tuple[float | None, float | None]]:
     return result
 
 
+def encode(location: tuple[float, float]) -> EncodedLocation:
+    """Encode a location."""
+
+    # Stub
+    return []
+
+
+def decode(location: EncodedLocation) -> tuple[float, float]:
+    """Decode into a location."""
+
+    # Stub
+    return (0.091659, 52.210796)
+
+
 def main():
+    """Testing."""
     print("Running query...")
     greggs = fetch_data("greggs")
     print(f"Query done - got {len(greggs)} Greggs!")