diff --git a/aoc_2024/src/day25.rs b/aoc_2024/src/day25.rs
new file mode 100644
index 0000000..3c46f61
--- /dev/null
+++ b/aoc_2024/src/day25.rs
@@ -0,0 +1,152 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Cell {
+    Empty,
+    Filled,
+}
+
+type Code = [usize; 5];
+
+type Input = (Vec<Code>, Vec<Code>);
+
+#[aoc_generator(day25)]
+fn parse(input: &str) -> Input {
+    let (keys, locks): (Vec<Option<Vec<Vec<Cell>>>>, Vec<Option<Vec<Vec<Cell>>>>) = input
+        .split("\n\n")
+        .map(|block| {
+            block
+                .lines()
+                .map(|line| {
+                    line.chars()
+                        .map(|c| match c {
+                            '.' => Cell::Empty,
+                            '#' => Cell::Filled,
+                            _ => panic!("Invalid cell"),
+                        })
+                        .collect()
+                })
+                .collect()
+        })
+        .map(|block: Vec<Vec<Cell>>| {
+            if block[0][0] == Cell::Filled {
+                (None, Some(block))
+            } else {
+                (Some(block), None)
+            }
+        })
+        .unzip();
+
+    let keys = keys
+        .into_iter()
+        .flatten()
+        .map(|block| {
+            let mut buffer = [0; 5];
+            for (y, row) in block.iter().enumerate() {
+                for x in 0..5 {
+                    if row[x] == Cell::Empty {
+                        buffer[x] = y;
+                    }
+                }
+            }
+            buffer
+        })
+        .collect();
+    let locks = locks
+        .into_iter()
+        .flatten()
+        .map(|block| {
+            let mut buffer = [0; 5];
+            for (y, row) in block.iter().enumerate() {
+                for x in 0..5 {
+                    if row[x] == Cell::Filled {
+                        buffer[x] = y;
+                    }
+                }
+            }
+            buffer
+        })
+        .collect();
+
+    (keys, locks)
+}
+
+#[aoc(day25, part1)]
+fn part1(input: &Input) -> usize {
+    let (keys, locks) = input;
+
+    let mut valid_combinations = 0;
+
+    for key in keys {
+        for lock in locks {
+            if (0..5).all(|i| key[i] >= lock[i]) {
+                valid_combinations += 1;
+            }
+        }
+    }
+
+    valid_combinations
+}
+
+// #[aoc(day25, part2)]
+// fn part2(input: &Input) -> usize {
+//     todo!()
+// }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(
+            part1(&parse(
+                "#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####"
+            )),
+            3
+        );
+    }
+
+    // #[test]
+    // fn part2_example() {
+    //     assert_eq!(part2(&parse("<EXAMPLE>")), 0);
+    // }
+}
diff --git a/aoc_2024/src/lib.rs b/aoc_2024/src/lib.rs
index c0a80e3..47fc1f9 100644
--- a/aoc_2024/src/lib.rs
+++ b/aoc_2024/src/lib.rs
@@ -1,7 +1,3 @@
-mod day24;
-mod day23;
-mod day22;
-mod day21;
 mod day1;
 mod day10;
 mod day11;
@@ -15,6 +11,11 @@ mod day18;
 mod day19;
 mod day2;
 mod day20;
+mod day21;
+mod day22;
+mod day23;
+mod day24;
+mod day25;
 mod day3;
 mod day4;
 mod day5;