diff --git a/src/day25.rs b/src/day25.rs
new file mode 100644
index 0000000..e2527b3
--- /dev/null
+++ b/src/day25.rs
@@ -0,0 +1,23 @@
+use crate::util::maps::World;
+
+pub fn day25() {
+    let keys_and_locks: Vec<World<bool>> = crate::input(25)
+        .split("\n\n")
+        .map(|keylock| World::from_string(keylock).map(|&c| c == '#'))
+        .collect();
+    let (locks, keys): (Vec<World<bool>>, Vec<World<bool>>) =
+        keys_and_locks.into_iter().partition(|key_or_lock| {
+            (0..key_or_lock.width()).all(|x| key_or_lock.get(x, 0) == Some(true))
+        });
+
+    let combos: usize = locks
+        .iter()
+        .map(|lock| keys.iter().filter(|key| fits(key, lock)).count())
+        .sum();
+    println!("There are {combos} combinations of keys and locks that work.");
+}
+
+fn fits(key: &World<bool>, lock: &World<bool>) -> bool {
+    !key.enumerate()
+        .any(|(x, y, c)| *c && lock.get(x, y) == Some(true))
+}
diff --git a/src/main.rs b/src/main.rs
index ac2726a..94c3f44 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -32,7 +32,9 @@ mod day21;
 mod day22;
 #[allow(dead_code)]
 mod day23;
+#[allow(dead_code)]
 mod day24;
+mod day25;
 #[allow(dead_code)]
 mod day3;
 #[allow(dead_code)]
@@ -49,7 +51,7 @@ mod day8;
 mod day9;
 
 fn main() {
-    day24::day24();
+    day25::day25();
 }
 
 pub fn input(day: u8) -> String {