diff --git a/day12/src/main.rs b/day12/src/main.rs
index bcd9154..7ba79af 100644
--- a/day12/src/main.rs
+++ b/day12/src/main.rs
@@ -1,33 +1,83 @@
+mod node;
+use node::Node;
+
 use aoc_shared::enums::Direction;
 use aoc_shared::grid::Grid as BaseGrid;
 use aoc_shared::impl_grid_newtype;
 
+#[derive(Debug, Copy, Clone, PartialEq)]
+enum CellType {
+    Start,
+    End,
+    Waypoint(u8),
+}
+
+#[derive(Debug, Clone)]
+struct Cell {
+    kind: CellType,
+    idx: usize,
+    coord: (usize, usize),
+}
+
+impl Cell {
+    pub fn new(kind: CellType, idx: usize, coord: (usize, usize)) -> Self {
+        Cell { kind, idx, coord }
+    }
+
+    pub fn get_height(&self) -> u8 {
+        match self.kind {
+            CellType::Start => 0,
+            CellType::End => 25,
+            CellType::Waypoint(c) => c,
+        }
+    }
+}
+
+// ----------------------------------------------------------------------------
+
 #[derive(Debug)]
 pub struct Grid<T>(BaseGrid<T>);
-impl_grid_newtype!(Grid, BaseGrid<char>, char);
+impl_grid_newtype!(Grid, BaseGrid<Cell>, Cell);
 
-impl Grid<char> {
+impl Grid<Cell> {
     pub fn from_file_str(file_str: &str) -> Self {
-        let lines: Vec<&str> = file_str.lines().collect();
-        let width = lines[0].len();
+        let first_line = file_str.lines().next().unwrap();
+        let width = first_line.len();
 
         let mut grid = Grid::new(width);
-        lines
-            .into_iter()
-            .map(|line| line.chars())
-            .for_each(|line_chars| grid.vec.append(&mut line_chars.collect::<Vec<char>>()));
+        let mut idx = 0usize;
+
+        for c in file_str.chars() {
+            let kind = match c {
+                'S' => CellType::Start,
+                'E' => CellType::End,
+                'a'..='z' => CellType::Waypoint(c as u8 - b'a'),
+                '\r' | '\n' => continue,
+                _ => panic!("Invalid character: {c}"),
+            };
+
+            let (x, y) = (idx % width, idx / width);
+            let cell = Cell::new(kind, idx, (x, y));
+
+            grid.vec.push(cell);
+
+            idx += 1;
+        }
 
         grid
     }
 
-    fn find_pos(&self, value: char) -> Option<usize> {
-        self.vec.iter().position(|item| *item == value)
+    fn find_pos(&self, value: CellType) -> Option<usize> {
+        self.vec.iter().position(|item| item.kind == value)
     }
 
     pub fn print(&self) {
         for r in 0usize..self.num_rows() {
             let range = self.row_first_idx(r)..=self.row_last_idx(r);
-            let line: String = self.vec[range].iter().collect();
+            let line: String = self.vec[range]
+                .iter()
+                .map(|n| (n.get_height() + b'a') as char)
+                .collect();
 
             println!("{}", line);
         }
@@ -78,35 +128,20 @@ impl Grid<char> {
             return false;
         }
 
-        // Is the character a lowercase letter?
-        let start_char = *start_char.unwrap();
-        let end_char = *end_char.unwrap();
-        if !(start_char.is_ascii_lowercase() && end_char.is_ascii_lowercase()) {
+        let start_char = start_char.unwrap();
+        let end_char = end_char.unwrap();
+        let start_elevation = start_char.get_height();
+        let end_elevation = end_char.get_height();
+        if (end_elevation < start_elevation) || end_elevation.abs_diff(start_elevation) > 1 {
             return false;
         }
 
-        // Is the elevation change 0 or 1?
-        let start_char = start_char
-            .to_digit(36)
-            .expect(&format!("Should be a digit: {}", start_char));
-        let end_char = end_char
-            .to_digit(36)
-            .expect(&format!("Should be a digit: {}", end_char));
-        let diff = u32::abs_diff(end_char, start_char);
-        if diff > 1  {
-            return false;
-        }
-
-        let (start_x, start_y) = self.idx_xy(start);
-        let (end_x, end_y) = self.idx_xy(end);
-        let x_diff = usize::abs_diff(end_x, start_x);
-        let y_diff = usize::abs_diff(end_y, start_y);
+        let ((start_x, start_y), (end_x, end_y)) = (start_char.coord, end_char.coord);
+        let x_diff = end_x.abs_diff(start_x);
+        let y_diff = end_y.abs_diff(start_y);
 
         // Have we moved 0 or 1 in a cardinal direction?
-        match (x_diff, y_diff) {
-            (0, 0) | (0, 1) | (1, 0) => true,
-            _ => false,
-        }
+        matches!((x_diff, y_diff), (0, 0) | (0, 1) | (1, 0))
     }
 
     fn find_moves(&self, start: usize) -> Vec<usize> {
@@ -116,11 +151,9 @@ impl Grid<char> {
             Direction::Left,
             Direction::Right,
         ]
-            .into_iter()
-            .map(|d| self.get_index_for_move(start, d))
-            .filter(|m| m.is_some())
-            .map(|m| m.unwrap())
-            .collect()
+        .into_iter()
+        .filter_map(|d| self.get_index_for_move(start, d))
+        .collect()
     }
 
     fn find_valid_moves(&self, start: usize) -> Vec<usize> {
@@ -131,117 +164,7 @@ impl Grid<char> {
     }
 
     fn has_valid_neighbor(&self, idx: usize) -> bool {
-        self.find_valid_moves(idx).len() > 0
-    }
-
-    fn filter_invalid(&mut self, from: usize) {
-        let (ch, col_indexes, row_indexes) = {
-            let ch = self.get(from).unwrap();
-            let (col, row) = self.idx_xy(from);
-            let col_indexes = self.get_column_indexes(col);
-            let row_indexes = self.get_row_indexes(row);
-
-            (ch, col_indexes, row_indexes)
-        };
-
-        self.vec = self.vec
-            .clone()
-            .into_iter()
-            .enumerate()
-            .map(|(idx, c)| {
-                if c != *ch {
-                    return c;
-                }
-
-                return if self.has_valid_neighbor(idx) && (col_indexes.contains(&idx) || row_indexes.contains(&idx)) {
-                    c
-                } else {
-                    '0'
-                }
-            })
-            .collect();
-
-    }
-}
-
-// ----------------------------------------------------------------------------
-
-#[derive(Debug, Default, Clone)]
-pub struct Node {
-    idx: usize,
-    parents: Vec<usize>,
-    children: Option<Vec<Box<Node>>>,
-}
-
-impl Node {
-    pub fn new(idx: usize) -> Self {
-        Node {
-            idx,
-            ..Node::default()
-        }
-    }
-
-    pub fn add_child(&mut self, value: usize) -> &mut Self {
-        let mut child = Node::new(value);
-        child.parents.append(&mut self.parents.clone());
-        child.parents.push(self.idx);
-
-        self.append(child);
-
-        self.children
-            .as_mut()
-            .expect("There should be a Vec here!")
-            .last_mut()
-            .expect("There should be a Box here!")
-    }
-
-    fn append(&mut self, node: Node) -> &mut Self {
-        match &mut self.children {
-            Some(c) => {
-                c.push(Box::new(node));
-            }
-            None => self.children = Some(vec![Box::new(node)]),
-        };
-
-        self
-    }
-
-    fn is_leaf(&self) -> bool {
-        self.children.is_none()
-    }
-
-    pub fn contains(&self, value: usize) -> bool {
-        if self.idx == value {
-            return true;
-        }
-
-        return self.parents.contains(&value);
-    }
-
-    pub fn get_leaves(&self) -> Vec<&Node> {
-        if self.is_leaf() {
-            return vec![self];
-        }
-
-        let mut leaves = Vec::new();
-
-        let children = self
-            .children
-            .as_ref()
-            .unwrap()
-            .iter()
-            .map(|boxed| boxed.as_ref());
-
-        for child in children {
-            let mut child_leaves = child.get_leaves();
-            leaves.append(&mut child_leaves);
-        }
-
-        leaves
-    }
-
-    pub fn get_len(&self) -> usize {
-        self.parents.len()
+        !self.find_valid_moves(idx).is_empty()
     }
 }
 
@@ -251,7 +174,7 @@ impl Node {
 pub struct Pathfinder {
     start_idx: usize,
     end_idx: usize,
-    grid: Grid<char>,
+    grid: Grid<Cell>,
     tree: Node,
 }
 
@@ -263,28 +186,21 @@ impl Pathfinder {
             grid: Grid::from_file_str(file_str),
             tree: Node::default(),
         };
-        pf.go_to_start();
+
+        let start = pf.grid.find_pos(CellType::Start).unwrap();
+        let end = pf.grid.find_pos(CellType::End).unwrap();
+
+        pf.start_idx = start;
+        pf.end_idx = end;
+        pf.tree.idx = start;
 
         pf
     }
 
-    fn go_to_start(&mut self) {
-        let start = self.grid.find_pos('S').unwrap();
-        let end = self.grid.find_pos('E').unwrap();
-
-        self.start_idx = start;
-        self.end_idx = end;
-        self.grid.vec[start] = 'a';
-        self.grid.vec[end] = 'z';
-        // self.grid.filter_invalid(start);
-
-        self.tree.idx = start;
-    }
-
     fn add_children(&mut self, node: &mut Node, idx: usize) {
         let possible_moves = self.grid.find_valid_moves(idx);
 
-        if possible_moves.len() == 0 {
+        if possible_moves.is_empty() {
             return;
         }
 
@@ -293,9 +209,9 @@ impl Pathfinder {
                 continue;
             }
 
-            let mut n = node.add_child(m);
+            let n = node.add_child(m);
             if m != self.end_idx {
-                self.add_children(&mut n, m);
+                self.add_children(n, m);
             } else {
                 break;
             }
@@ -310,7 +226,7 @@ impl Pathfinder {
         self.tree = tree;
     }
 
-    fn get_paths(&self) -> impl Iterator<Item= &Node> {
+    fn get_paths(&self) -> impl Iterator<Item = &Node> {
         self.tree
             .get_leaves()
             .into_iter()