diff --git a/day-3/.gitignore b/day-3/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/day-3/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/day-3/Cargo.lock b/day-3/Cargo.lock
new file mode 100644
index 0000000..d0411da
--- /dev/null
+++ b/day-3/Cargo.lock
@@ -0,0 +1,78 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "day-3"
+version = "0.1.0"
+dependencies = [
+ "indoc",
+]
+
+[[package]]
+name = "indoc"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47741a8bc60fb26eb8d6e0238bbb26d8575ff623fdc97b1a2c00c050b9684ed8"
+dependencies = [
+ "indoc-impl",
+ "proc-macro-hack",
+]
+
+[[package]]
+name = "indoc-impl"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce046d161f000fffde5f432a0d034d0341dc152643b2598ed5bfce44c4f3a8f0"
+dependencies = [
+ "proc-macro-hack",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "unindent",
+]
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
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+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8833e20724c24de12bbaba5ad230ea61c3eafb05b881c7c9d3cfe8638b187e68"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
+
+[[package]]
+name = "unindent"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f14ee04d9415b52b3aeab06258a3f07093182b88ba0f9b8d203f211a7a7d41c7"
diff --git a/day-3/Cargo.toml b/day-3/Cargo.toml
new file mode 100644
index 0000000..d861f49
--- /dev/null
+++ b/day-3/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "day-3"
+version = "0.1.0"
+authors = ["Tristan Daniël Maat <tm@tlater.net>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+indoc = "0.3"
diff --git a/day-3/input b/day-3/input
new file mode 100644
index 0000000..b4223c3
--- /dev/null
+++ b/day-3/input
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diff --git a/day-3/src/main.rs b/day-3/src/main.rs
new file mode 100644
index 0000000..b5c2d85
--- /dev/null
+++ b/day-3/src/main.rs
@@ -0,0 +1,91 @@
+use std::fs;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let input = fs::read_to_string("input")?;
+    let slope = parse_slope(&input)?;
+
+    // Part 1
+    let encounters = count_encounters(&slope, (1, 3));
+    println!("{}", encounters);
+
+    // Part 2
+    let encounters: usize = [(1, 1), (1, 3), (1, 5), (1, 7), (2, 1)]
+        .iter()
+        .map(|angle| count_encounters(&slope, *angle))
+        .product();
+    println!("{}", encounters);
+
+    Ok(())
+}
+
+fn parse_slope(input: &str) -> Result<Vec<Vec<usize>>, String> {
+    input
+        .lines()
+        .map(|line| {
+            line.chars()
+                .map(|c| match c {
+                    '.' => Ok(0),
+                    '#' => Ok(1),
+                    other => Err(format!("Invalid slope; contains character: {}", other)),
+                })
+                .collect()
+        })
+        .collect()
+}
+
+fn count_encounters(input: &Vec<Vec<usize>>, angle: (usize, usize)) -> usize {
+    input
+        .iter()
+        .enumerate()
+        .step_by(angle.0)
+        .map(|(i, row)| row[(i * angle.1 / angle.0) % row.len()])
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+
+    #[test]
+    fn test_simple() -> Result<(), Box<dyn std::error::Error>> {
+        let example = indoc!(
+            "..##.......
+             #...#...#..
+             .#....#..#.
+             ..#.#...#.#
+             .#...##..#.
+             ..#.##.....
+             .#.#.#....#
+             .#........#
+             #.##...#...
+             #...##....#
+             .#..#...#.#"
+        );
+
+        let parsed = parse_slope(example)?;
+        assert_eq!(count_encounters(&parsed, (1, 3)), 7);
+        Ok(())
+    }
+
+    #[test]
+    fn test_simple2() -> Result<(), Box<dyn std::error::Error>> {
+        let example = indoc!(
+            "..##.......
+             #...#...#..
+             .#....#..#.
+             ..#.#...#.#
+             .#...##..#.
+             ..#.##.....
+             .#.#.#....#
+             .#........#
+             #.##...#...
+             #...##....#
+             .#..#...#.#"
+        );
+
+        let parsed = parse_slope(example)?;
+        assert_eq!(count_encounters(&parsed, (2, 1)), 2);
+        Ok(())
+    }
+}