diff --git a/day17/Cargo.toml b/day17/Cargo.toml
new file mode 100644
index 0000000..e451294
--- /dev/null
+++ b/day17/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "day17"
+version = "0.1.0"
+authors = ["henine <why@no.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/day17/input b/day17/input
new file mode 100644
index 0000000..8d6105a
--- /dev/null
+++ b/day17/input
@@ -0,0 +1,8 @@
+..##.##.
+#.#..###
+##.#.#.#
+#.#.##.#
+###..#..
+.#.#..##
+#.##.###
+#.#..##.
\ No newline at end of file
diff --git a/day17/src/main.rs b/day17/src/main.rs
new file mode 100644
index 0000000..7ab2549
--- /dev/null
+++ b/day17/src/main.rs
@@ -0,0 +1,136 @@
+use std::cmp::{max, min};
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+use crate::ReactorCell::{Active, Inactive};
+
+type Reactor = HashMap<(i32, i32, i32, i32), ReactorCell>;
+
+#[derive(Copy, Clone, Debug)]
+enum ReactorCell {
+    Active(i32, i32, i32, i32),
+    Inactive(i32, i32, i32, i32),
+}
+
+impl ReactorCell {
+    fn new(state: char, x: i32, y: i32, z: i32, w: i32) -> Self {
+        match state {
+            '.' => Inactive(x, y, z, w),
+            '#' => Active(x, y, z, w),
+            _ => panic!()
+        }
+    }
+
+    fn update(&self, reactor: &Reactor) -> Option<ReactorCell> {
+        let (selfx, selfy, selfz, selfw) = match self {
+            Active(x, y, z, w) | Inactive(x, y, z, w) => (*x, *y, *z, *w)
+        };
+
+        let mut count = 0;
+        for x in -1..=1 {
+            for y in -1..=1 {
+                for z in -1..=1 {
+                    for w in -1..=1 {
+                        if x == 0 && y == 0 && z == 0 && w == 0 { continue; };
+                        count += match reactor.get(&(selfx + x, selfy + y, selfz + z, selfw + w)) {
+                            Some(Active(..)) => 1,
+                            None | Some(Inactive(..)) => 0
+                        }
+                    }
+                }
+            }
+        }
+
+        match self {
+            Inactive(x, y, z, w) => if count == 3 { Some(Active(*x, *y, *z, *w)) } else { None },
+            Active(x, y, z, w) => if count == 2 || count == 3 { Some(Active(*x, *y, *z, *w)) } else { None }
+        }
+    }
+}
+
+fn main() {
+    let file = File::open("input").unwrap();
+    let file_buffer = BufReader::new(file);
+    let mut lines = file_buffer.lines();
+
+
+    let mut reactor = Reactor::new();
+
+    let mut y = 0;
+    while let Some(Ok(line)) = lines.next() {
+        for (x, state) in line.chars().enumerate() {
+            reactor.insert((x as i32, y, 0, 0), ReactorCell::new(state, x as i32, y, 0, 0));
+        }
+        y += 1;
+    }
+
+    print_z(&reactor, 0);
+
+    for _ in 0..6 {
+        let mut new_reactor = Reactor::new();
+        let (min_x, min_y, min_z,min_w,
+            max_x, max_y, max_z, max_w) = get_boundaries(&reactor);
+        for x in min_x - 1..=max_x + 1 {
+            for y in min_y - 1..=max_y + 1 {
+                for z in min_z - 1..=max_z + 1 {
+                    for w in min_w-1..=max_w+1 {
+                        let new_cell = match reactor.get(&(x, y, z, w)) {
+                            Some(x) => x.update(&reactor),
+                            None => Inactive(x, y, z, w).update(&reactor)
+                        };
+
+                        match new_cell {
+                            Some(Active(x, y, z,w)) => new_reactor.insert((x, y, z,w), new_cell.unwrap()),
+                            Some(Inactive(..)) | None => None
+                        };
+                    }
+                }
+            }
+        }
+
+        reactor = new_reactor;
+        // for z in min_z..max_z {
+        //     println!("z={}", z);
+        //     print_z(&reactor, z)
+        // }
+    }
+
+    let count = reactor.values().filter(|cell| match cell {
+        Active(..) => true,
+        _ => false
+    }).count();
+    println!("{}", count);
+}
+
+fn print_z(reactor: &Reactor, z: i32) {
+    let (min_x, min_y, _, _, max_x, max_y, _, _) = get_boundaries(reactor);
+
+    for y in min_y..=max_y {
+        for x in min_x..=max_x {
+            print!("{}", match reactor.get(&(x, y, z, 0)) {
+                Some(Active(..)) => '#',
+                Some(Inactive(..)) | None => '.'
+            })
+        }
+        println!();
+    }
+    println!();
+}
+
+fn get_boundaries(reactor: &Reactor) -> (i32, i32, i32,i32,
+                                         i32, i32, i32,i32) {
+    reactor.iter()
+        .filter(|(_, state)| match state {
+            Active(..) => true,
+            Inactive(..) => false
+        })
+        .fold((i32::MAX, i32::MAX, i32::MAX, i32::MAX,
+               i32::MIN, i32::MIN, i32::MIN,i32::MIN),
+              |(minx, miny, minz, minw, maxx, maxy, maxz,maxw), ((x, y, z, w), _)| {
+                  (min(minx, *x), min(miny, *y), min(minz, *z), min(minw, *w),
+                   max(maxx, *x), max(maxy, *y), max(maxz, *z), max(maxw, *w))
+              }
+        )
+}
+
diff --git a/day17/test b/day17/test
new file mode 100644
index 0000000..17630fd
--- /dev/null
+++ b/day17/test
@@ -0,0 +1,3 @@
+.#.
+..#
+###
\ No newline at end of file