diff --git a/src/tasks/day20.rs b/src/tasks/day20.rs
index f82bb71..5a91f4d 100644
--- a/src/tasks/day20.rs
+++ b/src/tasks/day20.rs
@@ -2,12 +2,13 @@ use std::collections::{HashMap, HashSet, VecDeque};
 
 pub fn run() {
     let input = std::fs::read_to_string("input/day20.txt").unwrap();
-    let maze = Maze::from(&input);
+    let maze = Maze::from(&input, PortalField::create);
     let part1 = maze.shortest_path();
     println!("Part 1: {}", part1);
 }
 
 type C = i32;
+type FieldFactory = fn(&Point) -> Box<dyn Field>;
 
 #[derive(Hash, Eq, PartialEq, Copy, Clone, Debug)]
 struct Point {
@@ -30,48 +31,91 @@ impl Point {
     }
 }
 
-struct Field {
+trait Field {
+    fn neighbors(&self) -> Vec<Point>;
+    fn set_label_partner(&mut self, point: Point);
+    fn set_neighbors(&mut self, neighbors: Vec<Point>);
+    fn create(point: &Point) -> Box<dyn Field> where Self: Sized;
+}
+
+struct PortalField {
     neighbors: Vec<Point>,
 }
 
-impl Field {
-    fn of() -> Self {
-        Field { neighbors: vec![] }
+impl PortalField {
+    fn new() -> Self {
+        PortalField { neighbors: vec![] }
     }
 }
 
-pub struct Maze {
-    map: HashMap<Point, Field>,
+impl Field for PortalField {
+    fn neighbors(&self) -> Vec<Point> {
+        self.neighbors.clone()
+    }
+
+    fn set_label_partner(&mut self, point: Point) {
+        self.neighbors.push(point);
+    }
+
+    fn set_neighbors(&mut self, neighbors: Vec<Point>) {
+        self.neighbors = neighbors;
+    }
+
+    fn create(_: &Point) -> Box<dyn Field> where Self: Sized {
+        Box::new(PortalField::new())
+    }
+}
+
+//impl Field for PortalField {
+// fn neighbors(self, level: usize) -> Vec<Point> {
+//     if let Some((direction, p)) = self.dimension_neighbor {
+//         if direction == DimensionUp && level < 0 {
+//             let mut v = self.neighbors.clone();
+//             v.push(p);
+//             v
+//         } else {
+//             self.neighbors.clone()
+//         }
+//     } else {
+//         self.neighbors.clone()
+//     }
+// }
+//}
+
+type FieldMap = HashMap<Point, Box<dyn Field>>;
+
+struct Maze {
+    map: FieldMap,
     start: Point,
     finish: Point,
 }
 
 impl Maze {
-    pub fn from(input: &String) -> Self {
+    fn from(input: &String, field_factory: FieldFactory) -> Self {
         let (moc, width, height) = Self::map_of_chars(input);
 
-        let mut map = Self::create_map_of_free_spots(&moc);
+        let mut map = Self::create_map_of_free_spots(&moc, field_factory);
         Self::add_physical_neighbors(&mut map);
         let labels = Self::labels(&moc, width, height);
-        Self::add_portals(&mut map, &labels);
+        Self::process_labels(&mut map, &labels);
         let start = labels["AA"][0];
         let finish = labels["ZZ"][0];
 
         Maze { map, start, finish }
     }
 
-    pub fn shortest_path(&self) -> usize {
+    fn shortest_path(&self) -> usize {
         bfs(&self.map, self.start, self.finish)
     }
 
-    fn add_portals(map: &mut HashMap<Point, Field>, labels: &HashMap<String, Vec<Point>>) {
+    fn process_labels(map: &mut FieldMap, labels: &HashMap<String, Vec<Point>>) {
         for (label, points) in labels {
             if label == "AA" || label == "ZZ" {
                 continue;
             }
 
-            map.get_mut(&points[0]).unwrap().neighbors.push(points[1]);
-            map.get_mut(&points[1]).unwrap().neighbors.push(points[0]);
+            map.get_mut(&points[0]).unwrap().set_label_partner(points[1]);
+            map.get_mut(&points[1]).unwrap().set_label_partner(points[0]);
         }
     }
 
@@ -135,7 +179,7 @@ impl Maze {
         }
     }
 
-    fn add_physical_neighbors(map: &mut HashMap<Point, Field>) {
+    fn add_physical_neighbors(map: &mut FieldMap) {
         let points: HashSet<Point> = map.keys().map(|p| *p).collect();
         map.iter_mut().for_each(|(p, f)| {
             let neighbors = p
@@ -143,14 +187,14 @@ impl Maze {
                 .into_iter()
                 .filter(|neighbor| points.contains(neighbor))
                 .collect();
-            f.neighbors = neighbors;
+            f.set_neighbors(neighbors);
         })
     }
 
-    fn create_map_of_free_spots(moc: &HashMap<Point, char>) -> HashMap<Point, Field> {
+    fn create_map_of_free_spots(moc: &HashMap<Point, char>, field_factory: FieldFactory) -> FieldMap {
         moc.keys()
             .filter(|p| moc[p] == '.')
-            .map(|p| (*p, Field::of()))
+            .map(|p| (*p, field_factory(p)))
             .collect()
     }
 
@@ -179,7 +223,7 @@ impl Maze {
     }
 }
 
-fn bfs(map: &HashMap<Point, Field>, start: Point, finish: Point) -> usize {
+fn bfs(map: &FieldMap, start: Point, finish: Point) -> usize {
     let mut open: VecDeque<(Point, usize)> = VecDeque::new();
     let mut seen: HashSet<Point> = HashSet::new();
 
@@ -190,11 +234,11 @@ fn bfs(map: &HashMap<Point, Field>, start: Point, finish: Point) -> usize {
             return d;
         }
 
-        for neighbor in &map[&p].neighbors {
-            if !seen.contains(neighbor) {
-                open.push_back((*neighbor, d + 1));
+        for neighbor in map[&p].neighbors() {
+            if !seen.contains(&neighbor) {
+                open.push_back((neighbor, d + 1));
             }
-            seen.insert(*neighbor);
+            seen.insert(neighbor);
         }
     }
     panic!("no path found")
@@ -202,19 +246,19 @@ fn bfs(map: &HashMap<Point, Field>, start: Point, finish: Point) -> usize {
 
 #[cfg(test)]
 mod test {
-    use crate::tasks::day20::Maze;
+    use crate::tasks::day20::{Field, Maze, PortalField};
 
     #[test]
     fn example1() {
         let input = std::fs::read_to_string("input/day20_example1.txt").unwrap();
-        let maze = Maze::from(&input);
+        let maze = Maze::from(&input, PortalField::create);
         assert_eq!(maze.shortest_path(), 23);
     }
 
     #[test]
     fn result() {
         let input = std::fs::read_to_string("input/day20.txt").unwrap();
-        let maze = Maze::from(&input);
+        let maze = Maze::from(&input, PortalField::create);
         assert_eq!(maze.shortest_path(), 454);
     }
 }