diff --git a/day18/src/main.array3d.rs b/day18/src/main.array3d.rs
new file mode 100644
index 0000000..fc74155
--- /dev/null
+++ b/day18/src/main.array3d.rs
@@ -0,0 +1,93 @@
+use std::io;
+use std::env;
+use std::fs::File;
+use std::io::BufReader;
+use std::io::BufRead;
+use std::collections::HashSet;
+use std::collections::VecDeque;
+
+
+mod rustsux {
+    use std::fmt;
+
+    pub struct Array3D<T: Copy> {
+        backing_vec: Vec<T>,
+        pub d1: usize, pub d2: usize, pub d3: usize,
+    }
+
+    impl<T: Copy> Array3D<T> {
+        pub fn new(d1: usize, d2: usize, d3: usize, init: T) -> Array3D<T> {
+            Array3D {
+                backing_vec: vec![init; d1 * d2 * d3],
+                d1: d1, d2: d2, d3: d3,
+            }
+        }
+        pub fn get(&self, x: usize, y: usize, z: usize) -> T {
+            self.backing_vec[x*self.d2*self.d3 + y*self.d3 + z]
+        }
+        pub fn set(&mut self, x: usize, y: usize, z: usize, val: T) {
+            self.backing_vec[x*self.d2*self.d3 + y*self.d3 + z] = val;
+        }
+    }
+
+    impl<T: fmt::Display + Copy> fmt::Debug for Array3D<T> {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            for x in 0..self.d1 {
+                write!(f, "")?;
+                for y in 0..self.d2 {
+                    let row_start = x*self.d2*self.d3 + y*self.d3;
+                    let row_end = x*self.d2*self.d3 + (y + 1)*self.d3;
+                    for z in row_start..row_end {
+                        write!(f, "{}", self.backing_vec[z])?;
+                    }
+                    write!(f, " ")?;
+                }
+                writeln!(f, "")?;
+            }
+            Ok(())
+        }
+    }
+}
+
+
+fn floodfill_surface<T: Copy>(map: rustsux::Array3D<T>, block_sym: T) -> usize {
+    // TODO: start from arbitrary spot instead of 0, 0, 0
+    let mut queue = VecDeque::new();
+    queue.push_back((0, 0, 0));
+    while let Some((x, y, z)) = queue.pop_front() {
+        println!("{} {} {}", x, y, z);
+    }
+    0
+}
+
+
+fn main() -> io::Result<()> {
+    let input_fname = env::args().nth(1).expect("need input file");
+    let lines = BufReader::new(File::open(input_fname)?).lines();
+    let mut cubes: HashSet<(usize, usize, usize)> = HashSet::new();
+    let (mut max_x, mut max_y, mut max_z) = (0, 0, 0);
+
+    for line in lines.flatten() {
+        let mut split = line.split(',');
+        // +1 so that we have a guard plane at 0 index
+        let x = 1 + split.next().unwrap().to_string().parse::<usize>().unwrap();
+        let y = 1 + split.next().unwrap().to_string().parse::<usize>().unwrap();
+        let z = 1 + split.next().unwrap().to_string().parse::<usize>().unwrap();
+        cubes.insert((x, y, z));
+        max_x = if x > max_x {x} else {max_x};
+        max_y = if y > max_y {y} else {max_y};
+        max_z = if z > max_z {z} else {max_z};
+    }
+
+    let mut map = rustsux::Array3D::new(max_x + 1, max_y + 1, max_z + 1, '.');
+    for (x, y, z) in &cubes {
+        map.set(*x, *y, *z, '#');
+    }
+    println!("{} {} {}", max_x, max_y, max_z);
+    println!("{:?}", map);
+    floodfill_surface(map, '#');
+
+
+    Ok(())
+}
+
diff --git a/day18/src/main.rs b/day18/src/main.rs
index ba7fc15..89677ae 100644
--- a/day18/src/main.rs
+++ b/day18/src/main.rs
@@ -4,31 +4,60 @@ use std::fs::File;
 use std::io::BufReader;
 use std::io::BufRead;
 use std::collections::HashSet;
+use std::collections::VecDeque;
+
+type Map = HashSet<(i8, i8, i8)>;
+
+fn floodfill(cubes: Map, max_x: i8, max_y: i8, max_z: i8) -> usize {
+    let mut visited: Map = HashSet::new();
+    let mut surfaces = 0;
+    let mut queue = VecDeque::new();
+    queue.push_back((0, 0, 0));
+    println!("cubes = {:?}", cubes);
+    println!("maxes = {} {} {}", max_x, max_y, max_z);
+
+    while let Some((x, y, z)) = queue.pop_front() {
+        visited.insert((x, y, z));
+        let all_neighbors = HashSet::from([
+            (x + 1, y, z), (x - 1, y, z),
+            (x, y + 1, z), (x, y - 1, z),
+            (x, y, z + 1), (x, y, z - 1)
+        ]);
+        surfaces += all_neighbors.intersection(&cubes).count();
+        all_neighbors.difference(&cubes)
+            .filter(|&(x, y, z)|
+                *x >= 0 && *x <= max_x &&
+                *y >= 0 && *y <= max_y &&
+                *z >= 0 && *z <= max_z)
+            .filter(|&cube| !visited.contains(cube))
+            .for_each(|&cube|
+                if !queue.contains(&cube) {queue.push_back(cube)});
+    }
+    surfaces
+}
 
 
 fn main() -> io::Result<()> {
     let input_fname = env::args().nth(1).expect("need input file");
     let lines = BufReader::new(File::open(input_fname)?).lines();
-    let mut cubes: HashSet<(i8, i8, i8)> = HashSet::new();
+    let mut cubes: Map = HashSet::new();
+    let (mut max_x, mut max_y, mut max_z) = (0, 0, 0);
 
     for line in lines.flatten() {
         let mut split = line.split(',');
-        let x = split.next().unwrap().to_string().parse::<i8>().unwrap();
-        let y = split.next().unwrap().to_string().parse::<i8>().unwrap();
-        let z = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        // +1 so we have 3 guard planes at 0
+        let x = 1 + split.next().unwrap().to_string().parse::<i8>().unwrap();
+        let y = 1 + split.next().unwrap().to_string().parse::<i8>().unwrap();
+        let z = 1 + split.next().unwrap().to_string().parse::<i8>().unwrap();
         cubes.insert((x, y, z));
+        max_x = if x > max_x {x} else {max_x};
+        max_y = if y > max_y {y} else {max_y};
+        max_z = if z > max_z {z} else {max_z};
     }
 
-    let mut all_neighbors = 0;
-    for (x, y, z) in &cubes {
-        let neighbors = HashSet::from([
-            (*x + 1, *y, *z), (*x - 1, *y, *z),
-            (*x, *y + 1, *z), (*x, *y - 1, *z),
-            (*x, *y, *z + 1), (*x, *y, *z - 1)
-        ]);
-        all_neighbors += cubes.intersection(&neighbors).count();
-    }
-    println!("{}", cubes.len() * 6 - all_neighbors);
+    let surfaces = floodfill(cubes, max_x + 1, max_y + 1, max_z + 1);
+    println!("answer = {}", surfaces);
+
     Ok(())
 }
 
diff --git a/day18/src/main1.rs b/day18/src/main1.rs
new file mode 100644
index 0000000..ba7fc15
--- /dev/null
+++ b/day18/src/main1.rs
@@ -0,0 +1,34 @@
+use std::io;
+use std::env;
+use std::fs::File;
+use std::io::BufReader;
+use std::io::BufRead;
+use std::collections::HashSet;
+
+
+fn main() -> io::Result<()> {
+    let input_fname = env::args().nth(1).expect("need input file");
+    let lines = BufReader::new(File::open(input_fname)?).lines();
+    let mut cubes: HashSet<(i8, i8, i8)> = HashSet::new();
+
+    for line in lines.flatten() {
+        let mut split = line.split(',');
+        let x = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        let y = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        let z = split.next().unwrap().to_string().parse::<i8>().unwrap();
+        cubes.insert((x, y, z));
+    }
+
+    let mut all_neighbors = 0;
+    for (x, y, z) in &cubes {
+        let neighbors = HashSet::from([
+            (*x + 1, *y, *z), (*x - 1, *y, *z),
+            (*x, *y + 1, *z), (*x, *y - 1, *z),
+            (*x, *y, *z + 1), (*x, *y, *z - 1)
+        ]);
+        all_neighbors += cubes.intersection(&neighbors).count();
+    }
+    println!("{}", cubes.len() * 6 - all_neighbors);
+    Ok(())
+}
+