diff --git a/rust/2021/src/day_02.rs b/rust/2021/src/day_02.rs
index 8e50bab..486d8bb 100644
--- a/rust/2021/src/day_02.rs
+++ b/rust/2021/src/day_02.rs
@@ -1,9 +1,47 @@
 fn solve_part1(input: &str) -> i32 {
-    todo!()
+    let (horiz, _, depth) = solve(input);
+    horiz * depth
 }
 
 fn solve_part2(input: &str) -> i32 {
-    todo!()
+    let (horiz, depth, _) = solve(input);
+    horiz * depth
+}
+
+fn solve(input: &str) -> (i32, i32, i32) {
+    let (mut horiz, mut depth, mut aim) = (0, 0, 0);
+
+    for (dir, dist) in parse_input(input) {
+        match dir {
+            Some("forward") => {
+                horiz += dist;
+                depth += aim * dist;
+            }
+            Some("up") => aim -= dist,
+            Some("down") => aim += dist,
+            other => panic!("{:#?} is invalid", other),
+        }
+    }
+
+    (horiz, depth, aim)
+}
+
+fn parse_input(input: &str) -> Vec<(Option<&str>, i32)> {
+    input
+        .lines()
+        .map(|s| {
+            let mut it = s.split_whitespace();
+
+            let dir = it.next();
+            let dist = it
+                .next()
+                .map(|s| s.parse().ok())
+                .flatten()
+                .expect("parse &str as i32");
+
+            (dir, dist)
+        })
+        .collect()
 }
 
 pub fn run(input: String) {
@@ -15,4 +53,16 @@ pub fn run(input: String) {
 }
 
 #[cfg(test)]
-mod tests {}
+mod tests {
+    const PART_1_EXAMPLE_INPUT: &str = "forward 5\ndown 5\nforward 8\nup 3\ndown 8\nforward 2";
+
+    #[test]
+    fn part1() {
+        assert_eq!(super::solve_part1(PART_1_EXAMPLE_INPUT), 150);
+    }
+
+    #[test]
+    fn part2() {
+        assert_eq!(super::solve_part2(PART_1_EXAMPLE_INPUT), 900);
+    }
+}
diff --git a/rust/2021/src/day_03.rs b/rust/2021/src/day_03.rs
new file mode 100644
index 0000000..9c4c1ee
--- /dev/null
+++ b/rust/2021/src/day_03.rs
@@ -0,0 +1,30 @@
+fn solve_part1(input: &str) -> i32 {
+    todo!();
+}
+
+fn solve_part2(input: &str) -> i32 {
+    todo!();
+}
+
+pub fn run(input: String) {
+    println!("--- Part 1 ---");
+    println!("Answer: {}", solve_part1(&input));
+    println!();
+    println!("--- Part 2 ---");
+    println!("Answer: {}", solve_part2(&input))
+}
+
+#[cfg(test)]
+mod tests {
+    const EXAMPLE_INPUT: &str = todo!();
+
+    #[test]
+    fn part1() {
+        todo!();
+    }
+
+    #[test]
+    fn part2() {
+        todo!();
+    }
+}
diff --git a/rust/2021/src/day_template.rs b/rust/2021/src/day_template.rs
new file mode 100644
index 0000000..9c4c1ee
--- /dev/null
+++ b/rust/2021/src/day_template.rs
@@ -0,0 +1,30 @@
+fn solve_part1(input: &str) -> i32 {
+    todo!();
+}
+
+fn solve_part2(input: &str) -> i32 {
+    todo!();
+}
+
+pub fn run(input: String) {
+    println!("--- Part 1 ---");
+    println!("Answer: {}", solve_part1(&input));
+    println!();
+    println!("--- Part 2 ---");
+    println!("Answer: {}", solve_part2(&input))
+}
+
+#[cfg(test)]
+mod tests {
+    const EXAMPLE_INPUT: &str = todo!();
+
+    #[test]
+    fn part1() {
+        todo!();
+    }
+
+    #[test]
+    fn part2() {
+        todo!();
+    }
+}
diff --git a/rust/2021/src/lib.rs b/rust/2021/src/lib.rs
index 528d39d..bc1e2ab 100644
--- a/rust/2021/src/lib.rs
+++ b/rust/2021/src/lib.rs
@@ -1,6 +1,9 @@
 mod day_01;
 mod day_02;
+mod day_03;
+
+pub const INPUT_PATH: &str = "./input/2021/day3.txt";
 
 pub fn run(input: String) {
-    day_02::run(input);
+    day_03::run(input);
 }
diff --git a/rust/2021/src/main.rs b/rust/2021/src/main.rs
index a7c7479..ab779d7 100644
--- a/rust/2021/src/main.rs
+++ b/rust/2021/src/main.rs
@@ -1,4 +1,6 @@
+use advent_of_code_2021::INPUT_PATH;
+
 fn main() {
-    let input = std::fs::read_to_string("./input/2021/day2.txt").expect("open input file");
+    let input = std::fs::read_to_string(INPUT_PATH).expect("open input file");
     advent_of_code_2021::run(input);
 }