diff --git a/2016/13/Cargo.lock b/2016/13/Cargo.lock
new file mode 100644
index 0000000..7aac128
--- /dev/null
+++ b/2016/13/Cargo.lock
@@ -0,0 +1,4 @@
+[root]
+name = "13"
+version = "0.1.0"
+
diff --git a/2016/13/Cargo.toml b/2016/13/Cargo.toml
new file mode 100644
index 0000000..ae75f73
--- /dev/null
+++ b/2016/13/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "13"
+version = "0.1.0"
+authors = ["logaritmisk <anders.e.olsson@gmail.com>"]
+
+[dependencies]
diff --git a/2016/13/src/main.rs b/2016/13/src/main.rs
new file mode 100644
index 0000000..9157b17
--- /dev/null
+++ b/2016/13/src/main.rs
@@ -0,0 +1,291 @@
+use std::collections::{BTreeSet, BTreeMap};
+use std::usize;
+use std::fmt;
+
+
+type Cell = (usize, usize);
+
+
+#[derive(Debug, PartialEq, Copy, Clone)]
+pub enum Space {
+    Unknown,
+    Open,
+    Wall
+}
+
+pub struct Office {
+    seed: usize,
+    floor: Vec<Vec<Space>>
+}
+
+impl Office {
+    pub fn new(seed: usize) -> Self {
+        Office {
+            seed: seed,
+            floor: Vec::new()
+        }
+    }
+
+    pub fn cell_type(&mut self, cell: Cell) -> Space {
+        while cell.1 >= self.floor.len() {
+            self.floor.push(Vec::new());
+        }
+
+        while cell.0 >= self.floor[cell.1].len() {
+            self.floor[cell.1].push(Space::Unknown);
+        }
+
+        match self.floor[cell.1][cell.0] {
+            Space::Unknown => {
+                let integer = (cell.0 * cell.0) + (3 * cell.0) + (2 * cell.0 * cell.1) + cell.1 + (cell.1 * cell.1) + self.seed;
+
+                let binary = format!("{:b}", integer);
+
+                let ones = binary.chars()
+                    .filter(|x| *x == '1')
+                    .count();
+
+                if ones % 2 == 0 {
+                    self.floor[cell.1][cell.0] = Space::Open;
+                } else {
+                    self.floor[cell.1][cell.0] = Space::Wall;
+                }
+
+                self.floor[cell.1][cell.0]
+            }
+            s @ _ => {
+                s
+            }
+        }
+    }
+
+    fn cell_neighbors(&mut self, cell: Cell) -> Vec<Cell> {
+        let mut neighbors = Vec::new();
+
+        // Over.
+        if cell.1 > 0 {
+            if let Space::Open = self.cell_type((cell.0, cell.1 - 1)) {
+                neighbors.push((cell.0, cell.1 - 1));
+            }
+        }
+
+        // Below.
+        if let Space::Open = self.cell_type((cell.0, cell.1 + 1)) {
+            neighbors.push((cell.0, cell.1 + 1));
+        }
+
+        // Left.
+        if cell.0 > 0 {
+            if let Space::Open = self.cell_type((cell.0 - 1, cell.1)) {
+                neighbors.push((cell.0 - 1, cell.1));
+            }
+        }
+
+        // Right.
+        if let Space::Open = self.cell_type((cell.0 + 1, cell.1)) {
+            neighbors.push((cell.0 + 1, cell.1));
+        }
+
+        neighbors
+    }
+
+    pub fn path_between(&mut self, start: Cell, goal: Cell) -> Result<Vec<Cell>, ()> {
+        let mut closed_set = BTreeSet::new();
+        let mut open_set = BTreeSet::new();
+
+        open_set.insert(start);
+
+        let mut came_from = BTreeMap::new();;
+
+        let mut g_score = BTreeMap::new();
+
+        g_score.insert(start, 0);
+
+        let mut f_score = BTreeMap::new();
+
+        f_score.insert(start, heuristic_cost_estimate(start, goal));
+
+        while !open_set.is_empty() {
+            let (current, _) = f_score.iter()
+                .filter(|&(&(x, y), _)| open_set.contains(&(x, y)))
+                .fold(((0, 0), usize::MAX), |((min_x, min_y), min_score), (&(x, y), &score)| {
+                    if score < min_score {
+                        ((x, y), score)
+                    } else {
+                        ((min_x, min_y), min_score)
+                    }
+                });
+
+            if current == goal {
+                return Ok(reconstruct_path(&came_from, current));
+            }
+
+            open_set.remove(&current);
+            closed_set.insert(current);
+
+            for neighbor in self.cell_neighbors(current) {
+                if closed_set.contains(&neighbor) {
+                    continue;
+                }
+
+                let tentative_g_score = *g_score.entry(current).or_insert(usize::MAX) + dist_between(current, neighbor);
+
+                if !open_set.contains(&neighbor) {
+                    open_set.insert(neighbor);
+                } else if tentative_g_score >= *g_score.entry(neighbor).or_insert(usize::MAX) {
+                    continue
+                }
+
+                came_from.insert(neighbor, current);
+
+                g_score.insert(neighbor, tentative_g_score);
+                f_score.insert(neighbor, tentative_g_score + heuristic_cost_estimate(neighbor, goal));
+            }
+        }
+
+        Err(())
+    }
+
+}
+
+impl fmt::Display for Office {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        for row in self.floor.iter() {
+            for cell in row {
+                match *cell {
+                    Space::Unknown => { write!(f, " ")? },
+                    Space::Open    => { write!(f, ".")? },
+                    Space::Wall    => { write!(f, "#")? },
+                }
+            }
+
+            writeln!(f, "")?
+        }
+
+        Ok(())
+    }
+}
+
+
+fn reconstruct_path(came_from: &BTreeMap<Cell, Cell>, current: Cell) -> Vec<Cell> {
+    let mut current = current;
+    let mut path = Vec::new();
+
+    path.push(current);
+
+    while came_from.contains_key(&current) {
+        if let Some(next) = came_from.get(&current) {
+            current = *next;
+
+            path.push(*next);
+        }
+    }
+
+    path
+}
+
+fn dist_between(start: Cell, goal: Cell) -> usize {
+    let delta_x = goal.0 as i64 - start.0 as i64;
+    let delta_y = goal.1 as i64 - start.1 as i64;
+
+    (delta_x.abs() + delta_y.abs()) as usize
+}
+
+fn heuristic_cost_estimate(start: Cell, goal: Cell) -> usize {
+    dist_between(start, goal)
+}
+
+
+fn main() {
+    let mut office = Office::new(1352);
+
+    let path = office.path_between((1, 1), (31, 39)).unwrap();
+
+    for (y, row) in office.floor.iter().enumerate() {
+        for (x, cell) in row.iter().enumerate() {
+            if path.contains(&(x, y)) {
+                print!("\x1b[32m");
+            }
+
+            match *cell {
+                Space::Unknown => { print!(" "); },
+                Space::Open    => { print!("."); },
+                Space::Wall    => { print!("#"); },
+            }
+
+            if path.contains(&(x, y)) {
+                print!("\x1b[0m");
+            }
+        }
+
+        println!("");
+    }
+
+    println!("length={}", path.len() - 1);
+
+
+    let mut office = Office::new(1352);
+    let mut reachable = BTreeSet::new();
+
+    for x in 0..50 + 2 {
+        for y in 0..50 + 2 {
+            if let Ok(path) = office.path_between((1, 1), (x, y)) {
+                for cell in path.iter().rev().take(51) {
+                    reachable.insert(cell.clone());
+                }
+            }
+        }
+    }
+
+    for (y, row) in office.floor.iter().enumerate() {
+        for (x, cell) in row.iter().enumerate() {
+            if reachable.contains(&(x, y)) {
+                print!("\x1b[32m");
+            }
+
+            match *cell {
+                Space::Unknown => { print!(" "); },
+                Space::Open    => { print!("."); },
+                Space::Wall    => { print!("#"); },
+            }
+
+            if reachable.contains(&(x, y)) {
+                print!("\x1b[0m");
+            }
+        }
+
+        println!("");
+    }
+
+    println!("length={}", reachable.len());
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_cell_space() {
+        let mut office = Office::new(10);
+
+        assert_eq!(Space::Open, office.cell_type((0, 0)));
+        assert_eq!(Space::Wall, office.cell_type((1, 0)));
+        assert_eq!(Space::Open, office.cell_type((2, 0)));
+
+        assert_eq!(Space::Open, office.cell_type((0, 1)));
+        assert_eq!(Space::Open, office.cell_type((1, 1)));
+        assert_eq!(Space::Wall, office.cell_type((2, 1)));
+
+        assert_eq!(Space::Wall, office.cell_type((0, 2)));
+        assert_eq!(Space::Open, office.cell_type((1, 2)));
+        assert_eq!(Space::Open, office.cell_type((2, 2)));
+    }
+
+    #[test]
+    fn test_path_between() {
+        let mut office = Office::new(10);
+
+        assert_eq!(Ok(vec![(7, 4), (6, 4), (6, 5), (5, 5), (4, 5), (4, 4), (3, 4), (3, 3), (3, 2), (2, 2), (1, 2), (1, 1)]), office.path_between((1, 1), (7, 4)));
+    }
+}