diff --git a/day25/main.exs b/day25/main.exs
new file mode 100644
index 0000000..e56f4b1
--- /dev/null
+++ b/day25/main.exs
@@ -0,0 +1,51 @@
+defmodule Day25 do
+  def run do
+    %{locks: locks, keys: keys} = parse_input("data.txt")
+
+    # compare every key against every lock
+    good_keys =
+      Enum.reduce(keys, 0, fn key, acc ->
+        acc +
+          Enum.reduce(locks, 0, fn lock, acc2 ->
+            acc2 + if fits(lock, key), do: 1, else: 0
+          end)
+      end)
+
+    dbg(good_keys)
+  end
+
+  defp fits(lock, key) do
+    Enum.reduce(0..4, true, fn idx, acc ->
+      acc and Enum.at(lock, idx) + Enum.at(key, idx) <= 5
+    end)
+  end
+
+  defp parse_input(file) do
+    File.read!(file)
+    |> String.trim()
+    |> String.split("\n\n")
+    |> Enum.reduce(%{locks: [], keys: []}, fn el, %{locks: locks, keys: keys} = acc ->
+      grid = String.split(el, "\n") |> Enum.map(&String.graphemes/1)
+      is_lock = grid |> hd() |> hd() |> String.graphemes() |> Enum.all?(fn el -> el == "#" end)
+
+      res =
+        Enum.map(0..4, fn col ->
+          Enum.reduce(0..6, 0, fn row, acc2 ->
+            el = Enum.at(grid, row) |> Enum.at(col)
+
+            case el do
+              "#" -> acc2 + 1
+              _ -> acc2
+            end
+          end) - 1
+        end)
+
+      case is_lock do
+        true -> %{acc | locks: [res | locks]}
+        false -> %{acc | keys: [res | keys]}
+      end
+    end)
+  end
+end
+
+Day25.run()