diff --git a/2025/day_1.nix b/2025/day_1.nix
index 9bf69d5..766eaf0 100644
--- a/2025/day_1.nix
+++ b/2025/day_1.nix
@@ -9,7 +9,7 @@ with builtins;
 with import ./utils.nix;
 let
   # Split into non-empty lines
-  lines = builtins.filter (s: builtins.isString s && s != "") (builtins.split "\n" input);
+  lines = split "\n" input;
 
   # Parse a line like "L68" or "R14"
   parseLine = line: {
diff --git a/2025/day_2.nix b/2025/day_2.nix
new file mode 100644
index 0000000..8c9a67c
--- /dev/null
+++ b/2025/day_2.nix
@@ -0,0 +1,51 @@
+# nix eval -f ./day_2.nix part1
+# nix eval -f ./day_2.nix part1 --arg input 'builtins.readFile ./puzzle_cache/day_2_1'
+# nix eval -f ./day_2.nix part2
+# nix eval -f ./day_2.nix part2 --arg input 'builtins.readFile ./puzzle_cache/day_2_1'
+{
+  input ? (builtins.readFile ./puzzle_cache/day_2_0),
+}:
+with builtins;
+with import ./utils.nix;
+let
+  # reversedChars =
+  #   str:
+  #   let
+  #     len = length str;
+  #   in
+  #   builtins.genList (i: builtins.elemAt str (len - 1 - i)) len;
+  isStrPatternSplit =
+    str:
+    let
+      strLen = stringLength str;
+    in
+    (
+      if mod strLen 2 == 0 then
+        let
+          half = strLen / 2;
+          firstHalf = substring 0 half str;
+          secondHalf = substring half strLen str;
+          # secondReversed = reversedChars secondHalf;
+        in
+        firstHalf == secondHalf
+      else
+        false
+    );
+
+  ranges = map (range: map (v: toIntBase10 v) (split "-" range)) (split "," input);
+  fullRanges = map (itr: map (v: toString v) (rangeInclusive (elemAt itr 0) (elemAt itr 1))) ranges;
+  invalidIds = flatten (
+    map (
+      range:
+      (reduce (
+        invalidIds: id: invalidIds ++ (if isStrPatternSplit id then [ id ] else [ ])
+      ) [ ] range)
+    ) fullRanges
+  );
+  invalidIdNums = map (v: toIntBase10 v) invalidIds;
+  invalidIdSum = sum invalidIdNums;
+in
+{
+  part1 = invalidIdSum;
+  part2 = 0;
+}
diff --git a/2025/puzzle_cache/day_2_0 b/2025/puzzle_cache/day_2_0
new file mode 100644
index 0000000..a3f22ef
--- /dev/null
+++ b/2025/puzzle_cache/day_2_0
@@ -0,0 +1 @@
+11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124
diff --git a/2025/puzzle_cache/day_2_1 b/2025/puzzle_cache/day_2_1
new file mode 100644
index 0000000..f189b93
--- /dev/null
+++ b/2025/puzzle_cache/day_2_1
@@ -0,0 +1 @@
+96952600-96977512,6599102-6745632,32748217-32835067,561562-594935,3434310838-3434398545,150-257,864469-909426,677627997-677711085,85-120,2-19,3081-5416,34-77,35837999-36004545,598895-706186,491462157-491543875,5568703-5723454,6262530705-6262670240,8849400-8930122,385535-477512,730193-852501,577-1317,69628781-69809331,2271285646-2271342060,282-487,1716-2824,967913879-967997665,22-33,5722-11418,162057-325173,6666660033-6666677850,67640049-67720478,355185-381658,101543-146174,24562-55394,59942-93946,967864-1031782
diff --git a/2025/utils.nix b/2025/utils.nix
index 4921b82..406dc82 100644
--- a/2025/utils.nix
+++ b/2025/utils.nix
@@ -1,6 +1,20 @@
-{
-  toIntBase10 = str: builtins.fromJSON "${str}";
-  mod = a: b: a - b * (builtins.floor (a / b));
+with builtins;
+rec {
+  toIntBase10 = str: fromJSON "${str}";
+  mod = a: b: a - b * (floor (a / b));
   min = a: b: if a < b then a else b;
   max = a: b: if a > b then a else b;
+  split = delim: input: filter (s: isString s && s != "") (split delim input);
+  reduce = foldl'; # foldl' (acc: elem: acc + elem) 0 [1 2 3]
+  flatten = input: concatMap (x: if isList x then x else [ x ]) input;
+  rangeInclusive =
+    min: max:
+    if min > max then
+      [ ]
+    else
+      let
+        len = max - min + 1;
+      in
+      genList (i: min + i) len;
+  sum = input: reduce (sum: v: sum + v) 0 input;
 }