diff --git a/Cargo.toml b/Cargo.toml
index 14bfb68..6044e5e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -50,3 +50,7 @@ path = "src/day11.rs"
 [[bin]]
 name = "day12"
 path = "src/day12.rs"
+
+[[bin]]
+name = "day13"
+path = "src/day13.rs"
diff --git a/inputs/day13.txt b/inputs/day13.txt
new file mode 100644
index 0000000..227c901
--- /dev/null
+++ b/inputs/day13.txt
@@ -0,0 +1,804 @@
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+
+fold along x=655
+fold along y=447
+fold along x=327
+fold along y=223
+fold along x=163
+fold along y=111
+fold along x=81
+fold along y=55
+fold along x=40
+fold along y=27
+fold along y=13
+fold along y=6
diff --git a/src/day13.rs b/src/day13.rs
new file mode 100644
index 0000000..ebdb40b
--- /dev/null
+++ b/src/day13.rs
@@ -0,0 +1,91 @@
+use std::collections::HashSet;
+use std::str::FromStr;
+
+enum Axis {
+    X,
+    Y,
+}
+
+struct FoldInstruction {
+    axis: Axis,
+    position: usize,
+}
+
+impl FoldInstruction {
+    fn wrap(&self, dot: (usize, usize)) -> (usize, usize) {
+        match self.axis {
+            Axis::X if dot.0 >= self.position => (2 * self.position - dot.0, dot.1),
+            Axis::Y if dot.1 >= self.position => (dot.0, 2 * self.position - dot.1),
+            _ => (dot.0, dot.1),
+        }
+    }
+}
+
+impl FromStr for FoldInstruction {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<FoldInstruction, Self::Err> {
+        let (a, p) = s[11..].split_once('=').unwrap();
+        let axis = match a {
+            "x" => Axis::X,
+            "y" => Axis::Y,
+            _ => return Err(()),
+        };
+        let position = p.parse().unwrap();
+        Ok(FoldInstruction { axis, position })
+    }
+}
+
+fn main() {
+    const INPUT: &str = include_str!("../inputs/day13.txt");
+    let sections = INPUT.split_once("\n\n").unwrap();
+    let mut dots = sections
+        .0
+        .lines()
+        .map(|line| {
+            let (a, b) = line.split_once(',').unwrap();
+            (a.parse().unwrap(), b.parse().unwrap())
+        })
+        .collect::<Vec<(usize, usize)>>();
+    let instructions = sections
+        .1
+        .lines()
+        .map(|line| line.parse().unwrap())
+        .collect::<Vec<FoldInstruction>>();
+
+    let mut all_dots: HashSet<(usize, usize)> = HashSet::new();
+    for dot in dots.iter() {
+        all_dots.insert(instructions[0].wrap(*dot));
+    }
+    println!("solution {}", all_dots.len());
+
+    all_dots.drain();
+    for instr in instructions {
+        for dot in dots.iter() {
+            all_dots.insert(instr.wrap(*dot));
+        }
+        dots = all_dots.drain().collect();
+    }
+    for y in 0..6 {
+        println!(
+            "{}",
+            (0..40)
+                .map(|x| if dots.contains(&(x, y)) {
+                    '🟪'
+                } else {
+                    '⬛'
+                })
+                .collect::<String>()
+        );
+    }
+}
+
+#[test]
+fn test_wrap_instruction() {
+    let instruction = FoldInstruction {
+        axis: Axis::Y,
+        position: 7,
+    };
+    assert_eq!(instruction.wrap((3, 0)), (3, 0));
+    assert_eq!(instruction.wrap((1, 10)), (1, 4));
+}