diff --git a/inputs/day04example.exe b/inputs/day04example.exe
new file mode 100644
index 0000000..8209399
--- /dev/null
+++ b/inputs/day04example.exe
@@ -0,0 +1,10 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.
diff --git a/src/bin/day04.rs b/src/bin/day04.rs
new file mode 100644
index 0000000..2c2802f
--- /dev/null
+++ b/src/bin/day04.rs
@@ -0,0 +1,12 @@
+use aoc_2025::day04;
+use color_eyre::Report;
+
+fn main() -> Result<(), Report> {
+    color_eyre::install()?;
+    let data = day04::data("inputs/day04example.txt")?;
+    let code1 = day04::part1(&data)?;
+    let code2 = day04::part2(&data)?;
+    println!("code1: {code1}");
+    println!("code2: {code2}");
+    Ok(())
+}
diff --git a/src/day04.rs b/src/day04.rs
new file mode 100644
index 0000000..19615a7
--- /dev/null
+++ b/src/day04.rs
@@ -0,0 +1,85 @@
+use color_eyre::{Report, eyre::ContextCompat};
+use std::{
+    fs::File,
+    io::{self, BufRead, BufReader, Lines},
+};
+
+struct Wall {
+    inner: Vec<bool>,
+    width: usize,
+    height: usize,
+}
+
+impl<R: BufRead> TryFrom<Lines<R>> for Wall {
+    type Error = Report;
+    fn try_from(mut value: Lines<R>) -> Result<Self, Self::Error> {
+        let width = None;
+        while let Some(line) = value.next() {
+            let line = line?;
+            let chars: Vec<char> = line.chars().collect();
+            let new_width = chars.len();
+            if let Some(old_width) = width {
+                return Err();
+            }
+            let mut inner: Vec<bool> = Vec::with_capacity(width);
+            for c in chars {
+                match c {
+                    '#' => inner.push(true),
+                    '.' => inner.push(false),
+                    _ => return Err(Report::msg(format!("Invalid character in wall: {}", c))),
+                }
+            }
+            let height = 1;
+        }
+        Ok(Self {
+            inner,
+            width,
+            height,
+        })
+    }
+}
+
+pub fn part1(data: &Wall) -> Result<u64, Report> {
+    // Ok(data
+    //     .iter()
+    //     .map(|v| v.part1())
+    //     .collect::<Result<Vec<u64>, Report>>()?
+    //     .iter()
+    //     .sum::<u64>())
+    Ok(0)
+}
+
+pub fn part2(data: &Wall) -> Result<u64, Report> {
+    // let first = BatteryBank::try_from(String::from("818181911112111"))?.part2()?;
+    // Ok(data
+    //     .iter()
+    //     .map(|v| v.part2())
+    //     .collect::<Result<Vec<u64>, Report>>()?
+    //     .iter()
+    //     .sum::<u64>())
+    Ok(0)
+}
+pub fn data(filepath: &str) -> Result<Wall, Report> {
+    let file = File::open(filepath)?;
+    let bufreader = BufReader::new(file);
+    let wall = Wall::try_from(bufreader.lines())?;
+    Ok(wall)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use criterion::Criterion;
+    use criterion_macro::criterion;
+
+    #[criterion]
+    fn bench_part1(b: &mut Criterion) {
+        let data = data("inputs/day04.txt").unwrap();
+        b.bench_function("day04-part1", |b| b.iter(|| part1(&data).unwrap()));
+    }
+    #[criterion]
+    fn bench_part2(b: &mut Criterion) {
+        let data = data("inputs/day04.txt").unwrap();
+        b.bench_function("day04-part2", |b| b.iter(|| part2(&data).unwrap()));
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 866948c..512b045 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,3 +5,4 @@ extern crate test;
 pub mod day01;
 pub mod day02;
 pub mod day03;
+pub mod day04;