diff --git a/day11/Cargo.toml b/day11/Cargo.toml
index 2f24ab3..5f54999 100644
--- a/day11/Cargo.toml
+++ b/day11/Cargo.toml
@@ -7,4 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+enum-map = "0.6.4"
 ndarray = "0.14.0"
+strum = "0.20.0"
+strum_macros = "0.20.1"
diff --git a/day11/src/binary.rs b/day11/src/binary.rs
new file mode 100644
index 0000000..b015095
--- /dev/null
+++ b/day11/src/binary.rs
@@ -0,0 +1,104 @@
+use enum_map::Enum;
+use strum_macros::EnumIter;
+
+#[derive(Clone, Copy, Enum, Eq, PartialEq)]
+pub enum State {
+    None,
+    Floor,
+    SeatEmpty,
+    SeatOccupied,
+}
+
+impl Default for State {
+    fn default() -> Self { Self::None }
+}
+
+impl State {
+    fn from_number(number: u8) -> Self {
+        match number {
+            0 => Self::None,
+            1 => Self::Floor,
+            2 => Self::SeatEmpty,
+            3 => Self::SeatOccupied,
+            _ => panic!("unsupported number {}", number),
+        }
+    }
+
+    fn get_number(&self) -> u8 {
+        match self {
+            Self::None => 0, // border should always be 0
+            Self::Floor => 1,
+            Self::SeatEmpty => 2,
+            Self::SeatOccupied => 3,
+        }
+    }
+}
+
+#[derive(Copy, Clone, Enum, EnumIter)]
+pub enum Direction {
+    UpLeft,
+    Up,
+    UpRight,
+    Left,
+    Right,
+    DownLeft,
+    Down,
+    DownRight,
+}
+
+impl Direction {
+    fn get_offset(&self) -> u16 {
+        match self {
+            Self::UpLeft => 0,
+            Self::Up => 2,
+            Self::UpRight => 4,
+            Self::Left => 6,
+            Self::Right => 8,
+            Self::DownLeft => 10,
+            Self::Down => 12,
+            Self::DownRight => 14,
+        }
+    }
+}
+
+pub struct CellState {
+    neighbours_states: u16,
+    state: u8,
+}
+
+impl CellState {
+    pub fn new() -> Self {
+        Self {
+            neighbours_states: 0,
+            state: 0,
+        }
+    }
+
+    pub fn update_neighbour_state(&mut self, direction: Direction, new_state: State) -> () {
+        self.neighbours_states = (self.neighbours_states & !(0b11 << direction.get_offset())) | ((new_state.get_number() as u16) << direction.get_offset());
+    }
+
+    pub fn update_state(&mut self, new_state: State) {
+        self.state = new_state.get_number();
+    }
+
+    pub fn from_number(number: u32) -> Self {
+        CellState {
+            state: (number >> 16) as u8,
+            neighbours_states: (number & 0xffff) as u16,
+        }
+    }
+
+    pub fn get_number(&self) -> u32 {
+        ((self.state as u32) << 16) | (self.neighbours_states as u32)
+    }
+
+    pub fn get_state(&self) -> State {
+        State::from_number(self.state)
+    }
+
+    pub fn get_neighbour_state(&self, direction: Direction) -> State {
+        State::from_number(((self.neighbours_states >> direction.get_offset()) & 0b11) as u8)
+    }
+}
+
diff --git a/day11/src/board_metadata.rs b/day11/src/board_metadata.rs
new file mode 100644
index 0000000..f5b1c24
--- /dev/null
+++ b/day11/src/board_metadata.rs
@@ -0,0 +1,85 @@
+use std::default::Default;
+use std::ops::{Index, IndexMut};
+use ndarray::Array2;
+
+use crate::binary::Direction;
+
+#[derive(Copy, Clone)]
+pub struct CellLocation {
+    row: usize,
+    column: usize,
+}
+
+impl CellLocation {
+    pub fn new(row: usize, column: usize) -> Self {
+        Self {
+            row,
+            column,
+        }
+    }
+
+    fn new_option(row_option: Option<usize>, column_option: Option<usize>) -> Option<Self> {
+        match (row_option, column_option) {
+            (Some(row), Some(column)) => Some(Self::new(row, column)),
+            _ => None,
+        }
+    }
+}
+
+impl<T> Index<CellLocation> for Array2<T> {
+    type Output = T;
+    fn index<'a>(&'a self, cell_location: CellLocation) -> &'a T {
+        &self[[cell_location.row, cell_location.column]]
+    }
+}
+
+impl<T> IndexMut<CellLocation> for Array2<T> {
+    fn index_mut<'a>(&'a mut self, cell_location: CellLocation) -> &'a mut T {
+        &mut self[[cell_location.row, cell_location.column]]
+    }
+}
+
+pub struct BoardMetadata {
+    rows: usize,
+    columns: usize,
+}
+
+impl BoardMetadata {
+    pub fn new(rows: usize, columns: usize) -> Self {
+        BoardMetadata {
+            rows,
+            columns,
+        }
+    }
+
+    pub fn get_neighbour_location(&self, cell_location: CellLocation, direction: Direction) -> Option<CellLocation> {
+        let row = cell_location.row;
+        let column = cell_location.column;
+
+        let up = if row > 0 { Some(row-1) } else { None };
+        let middle = Some(row);
+        let down = if row < self.rows-1 { Some(row+1) } else { None };
+        let left = if column > 0 { Some(column-1) } else { None };
+        let center = Some(column);
+        let right = if column < self.columns-1 { Some(column+1) } else { None };
+
+        match direction {
+            Direction::UpLeft => CellLocation::new_option(up, left),
+            Direction::Up => CellLocation::new_option(up, center),
+            Direction::UpRight => CellLocation::new_option(up, right),
+            Direction::Left => CellLocation::new_option(middle, left),
+            Direction::Right => CellLocation::new_option(middle, right),
+            Direction::DownLeft => CellLocation::new_option(down, left),
+            Direction::Down => CellLocation::new_option(down, center),
+            Direction::DownRight => CellLocation::new_option(down, right),
+        }
+    }
+
+    pub fn create_board_default<T: Default>(&self) -> Array2<T> {
+        Array2::default((self.rows, self.columns))
+    }
+
+    pub fn create_board_from_shape_fn<T, F: Fn(CellLocation) -> T>(&self, f: F) -> Array2<T> {
+        Array2::from_shape_fn((self.rows, self.columns), |(row, column)| f(CellLocation::new(row, column)))
+    }
+}
diff --git a/day11/src/game.rs b/day11/src/game.rs
new file mode 100644
index 0000000..def8bc7
--- /dev/null
+++ b/day11/src/game.rs
@@ -0,0 +1,161 @@
+use enum_map::EnumMap;
+use ndarray::Array2;
+use strum::IntoEnumIterator;
+
+use crate::binary::CellState;
+use crate::binary::Direction;
+use crate::binary::State;
+use crate::board_metadata::BoardMetadata;
+use crate::board_metadata::CellLocation;
+use crate::rules::Rules;
+
+struct CellInfo {
+    neighbours: EnumMap<Direction, Option<CellLocation>>,
+    state: CellState,
+}
+
+impl CellInfo {
+    fn new(neighbours: EnumMap<Direction, Option<CellLocation>>) -> CellInfo {
+        CellInfo {
+            neighbours,
+            state: CellState::new(),
+        }
+    }
+
+    fn update_neighbour_state(&mut self, direction: Direction, new_state: State) -> () {
+        self.state.update_neighbour_state(direction, new_state)
+    }
+
+    fn update_state(&mut self, new_state: State) {
+        self.state.update_state(new_state)
+    }
+}
+
+pub struct Game {
+    cell_rules: Vec<State>,
+    board: Array2<CellInfo>,
+    rows: usize,
+    columns: usize,
+}
+
+impl Game {
+    // only updates the state of this cell for it and its neighbours;
+    // only state of this cell is used from new_cell
+    fn update_cell(&mut self, location: CellLocation, new_state: State) {
+        //println!("Updating cell {}:{}", location.row, location.column);
+        self.board[location].update_state(new_state);
+
+        for direction in Direction::iter() {
+            match self.board[location].neighbours[direction] {
+                Some(neighbour_location) => {
+                    //println!("Updating neighbour cell {}:{}", neighbour_location.row, neighbour_location.column);
+                    self.board[neighbour_location].update_neighbour_state(direction, new_state);
+                },
+                _ => {},
+            }
+        }
+    }
+
+    fn build_cell_rules<T: Rules>() -> Vec<State> {
+        let mut result = vec![State::None; 1 << 18];
+
+        for i in 0..1usize << 18 {
+            let original_state = CellState::from_number(i as u32);
+            let mut neighbour_counts = EnumMap::new();
+            for direction in Direction::iter() {
+                neighbour_counts[original_state.get_neighbour_state(direction)] += 1usize;
+            }
+
+            let new_state = T::get_next_state(original_state.get_state(), neighbour_counts);
+            result[i] = new_state;
+            //println!("Rule #{}: for state_counts [{}, {}, {}, {}] and old state {} new state is {}", i, state_counts[0], state_counts[1], state_counts[2], state_counts[3], current_state, new_state);
+        }
+
+        result
+    }
+
+    fn get_next_state(&self, cell_info: &CellInfo) -> State {
+        self.cell_rules[cell_info.state.get_number() as usize]
+    }
+
+    pub fn next_step(&mut self) -> usize {
+        let mut changes: Vec<_> = vec![];
+        for row in 0..self.rows {
+            for column in 0..self.columns {
+                let location = CellLocation::new(row, column);
+                let cell = &self.board[location];
+                let next_state = self.get_next_state(cell);
+                //println!("location: {}:{}, neighbours state {}, old state {}, next state {}", location.row, location.column, cell.neighbours_states, cell.state, next_state);
+                if next_state != cell.state.get_state() {
+                    changes.push((location, next_state));
+                }
+            }
+        }
+
+        let changes_count = changes.len();
+        for (location, new_state) in changes {
+            self.update_cell(location, new_state);
+        }
+
+        changes_count
+    }
+
+    pub fn from_input<R: Rules>(input_data: &[String]) -> Self {
+        let rows = input_data.len();
+        let columns = input_data[0].len();
+        let board_metadata = BoardMetadata::new(rows, columns);
+        let mut states = board_metadata.create_board_default();
+
+        for row in 0..rows {
+            let chars = input_data[row].chars().collect::<Vec<_>>();
+            for column in 0..columns {
+                let ch = chars[column];
+                states[[row, column]] = match ch {
+                    '.' => State::Floor,
+                    'L' => State::SeatEmpty,
+                    '#' => State::SeatOccupied,
+                    _ => State::None,
+                }
+            }
+        }
+
+        let board = board_metadata.create_board_from_shape_fn(|cell_location| {
+            CellInfo::new(R::get_neighbours(cell_location, &board_metadata, &states))
+        });
+
+        let cell_rules = Self::build_cell_rules::<R>();
+
+        let mut game = Game {
+            rows,
+            columns,
+            board,
+            cell_rules,
+        };
+
+        for row in 0..rows {
+            for column in 0..columns {
+                let location = CellLocation::new(row, column);
+                game.update_cell(location, states[location]);
+            }
+        }
+
+        return game;
+    }
+
+    pub fn print_board(&self) {
+        for row in (&self.board).genrows() {
+            println!("{}", row.iter().map(|cell| {
+                match cell.state.get_state() {
+                    State::Floor => '.',
+                    State::SeatEmpty => 'L',
+                    State::SeatOccupied => '#',
+                    State::None => '0',
+                }
+            }).collect::<String>());
+        }
+    }
+
+    pub fn get_count_of_cells_for_state(&self, state: State) -> usize {
+        (&self.board).iter().filter(|&cell| cell.state.get_state() == state).count()
+    }
+}
diff --git a/day11/src/main.rs b/day11/src/main.rs
index f6d04fa..44fa209 100644
--- a/day11/src/main.rs
+++ b/day11/src/main.rs
@@ -1,193 +1,33 @@
 #![feature(trait_alias)]
 
 use std::io::{self, BufRead};
-use ndarray::Array2;
 
-// state (u32 for simplicity reasons): 0/1/2/3 (in this case, 1 = floor, 2 = seat free, 3 = seat taken)
+mod binary;
+mod board_metadata;
+mod game;
+mod rules;
+mod rules_easy;
 
-// every cell is u32, where:
-// * lowest 16 bits describe its neighbours:
-//     * bits 0-1 (cell & 3) is the state of upper left neighbour,
-//     * bits 2-3 ((cell >> 2) & 3) is the state of upper neighbour,
-//     * bits 4-5 is the state of upper right neighbour,
-//     * bits 6-7, left,
-//     * bits 8-9, right,
-//     * bits 10-11, bottom left,
-//     * bits 12-13, bottom,
-//     * bits 14-15, bottom right
-// * bits 16-17 ((cell >> 16) & 3) describe the cell itself
-
-// rule: cell (u32, 18 bits used) -> new cell (u32)
-
-// board is indexed by [row, column],
-// where row is from top to bottom and column is from left to right
-
-trait StateRules = Fn([usize; 4], u32) -> u32;
-
-struct Game {
-    cell_rules: Vec<u32>,
-    board: Array2<u32>,
-    rows: usize,
-    columns: usize,
-}
-
-impl Game {
-    // only updates the state of this cell for it and its neighbours;
-    // only state of this cell is used from new_cell
-    fn update_cell(&mut self, row: usize, column: usize, new_cell: u32) {
-        let state_diff = (new_cell ^ self.board[[row, column]]) >> 16;
-
-        self.board[[row, column]] ^= state_diff << 16;
-
-        self.board[[row+1, column+1]] ^= state_diff;
-        self.board[[row+1, column  ]] ^= state_diff <<  2;
-        self.board[[row+1, column-1]] ^= state_diff <<  4;
-        self.board[[row  , column+1]] ^= state_diff <<  6;
-        self.board[[row  , column-1]] ^= state_diff <<  8;
-        self.board[[row-1, column+1]] ^= state_diff << 10;
-        self.board[[row-1, column  ]] ^= state_diff << 12;
-        self.board[[row-1, column-1]] ^= state_diff << 14;
-    }
-
-    fn build_cell_rules<T: StateRules>(state_rules: T) -> Vec<u32> {
-        let mut result = vec![0u32; 1 << 18];
-
-        for i in 0..1usize << 18 {
-            let cell = i as u32;
-            let current_state = (cell >> 16) & 3;
-            let mut state_counts = [0usize; 4];
-            for j in 0..8 {
-                state_counts[((cell >> (2*j)) & 3) as usize] += 1;
-            }
-
-            let new_state = state_rules(state_counts, current_state);
-            let new_cell = cell ^ ((current_state ^ new_state) << 16);
-            result[i] = new_cell;
-        }
-
-        result
-    }
-
-    pub fn next_step(&mut self) -> usize {
-        let mut changes: Vec<_> = vec![];
-        for row in 1..self.rows-1 {
-            for column in 1..self.columns-1 {
-                let old_cell = self.board[[row, column]];
-                let new_cell = self.cell_rules[old_cell as usize];
-                if new_cell != old_cell {
-                    changes.push((row, column, new_cell));
-                }
-            }
-        }
-
-        let changes_count = changes.len();
-        for (row, column, new_cell) in changes {
-            self.update_cell(row, column, new_cell);
-        }
-
-        changes_count
-    }
-
-    pub fn from_input<T: StateRules>(input_data: &[String], state_rules: T) -> Game {
-        let rows = input_data.len() + 2;
-        let columns = input_data[0].len() + 2;
-        let mut states = Array2::zeros((rows, columns));
-
-        for row in 1..rows-1 {
-            let chars = input_data[row-1].chars().collect::<Vec<_>>();
-            for column in 1..columns-1 {
-                let ch = chars[column-1];
-                states[[row, column]] = match ch {
-                    '.' => 1,
-                    'L' => 2,
-                    '#' => 3,
-                    _ => 0,
-                }
-            }
-        }
-
-        let mut board = Array2::zeros((rows, columns));
-
-        /*
-        board[[0, 0]] = states[[1, 1]] << 14;
-        board[[0, columns-1]] = states[[1, columns-2]] << 10;
-        board[[rows-1, 0]] = states[[rows-2, 1]] << 4;
-        board[[rows-1, columns-1]] = states[[rows-2, columns-2]];
-
-        for row in 1..rows-1 {
-            board[[row, 0]] = (states[[row-1, 1]] << 4) ^ (states[[row, 1]] << 8) ^ (states[[row+1, 1]] << 14);
-            board[[row, columns-1]] = (states[[row-1, columns-2]]) ^ (states[[row, columns-2]] << 6) ^ (states[[row+1, columns-2]] << 10);
-        }
-
-        for column in 1..columns-1 {
-            board[[0, column]] = (states[[1, column-1]] << 10) ^ (states[[1, column]] << 12) ^ (states[[1, column+1]] << 14);
-            board[[rows-1, column]] = (states[[rows-2, column-1]]) ^ (states[[rows-2, column]] << 2) ^ (states[[rows-2, column+1]] << 4);
-        }
-        */
-
-        for row in 1..rows-1 {
-            for column in 1..columns-1 {
-                board[[row, column]] =
-                    (states[[row-1, column-1]]      ) ^
-                    (states[[row-1, column  ]] <<  2) ^
-                    (states[[row-1, column+1]] <<  4) ^
-                    (states[[row  , column-1]] <<  6) ^
-                    (states[[row  , column+1]] <<  8) ^
-                    (states[[row+1, column-1]] << 10) ^
-                    (states[[row+1, column  ]] << 12) ^
-                    (states[[row+1, column+1]] << 14) ^
-                    (states[[row, column]] << 16);
-            }
-        }
-
-        let cell_rules = Self::build_cell_rules(state_rules);
-
-        Game {
-            rows,
-            columns,
-            board,
-            cell_rules,
-        }
-    }
-
-    pub fn print_board(&self) {
-        for row in (&self.board).genrows() {
-            println!("{}", row.iter().map(|state| {
-                match (state >> 16) & 3 {
-                    1 => '.',
-                    2 => 'L',
-                    3 => '#',
-                    _ => '0',
-                }
-            }).collect::<String>());
-        }
-    }
-
-    pub fn get_count_of_cells_for_state(&self, state: u32) -> usize {
-        (&self.board).iter().filter(|&&cell| ((cell >> 16) & 3) == state).count()
-    }
-}
+use binary::State;
+use game::Game;
+use rules_easy::RulesEasy;
 
 fn main() {
     let stdin = io::stdin();
     let lines: Vec<_> = stdin.lock().lines().map(|line| line.unwrap()).collect();
-    let mut game = Game::from_input(&lines, |state_counts: [usize; 4], current_state| {
-        match current_state {
-            2 => if state_counts[3] == 0 { 3 } else { 2 },
-            3 => if state_counts[3] >= 4 { 2 } else { 3 },
-            other => other
-        }
-    });
+    let mut game = Game::from_input::<RulesEasy>(&lines);
+
+    //game.print_board();
 
     for i in 1.. {
         let changes_count = game.next_step();
         println!("Iteration {}; changed cells: {}", i, changes_count);
+        //game.print_board();
         if changes_count == 0 {
             break;
         }
     }
 
-    println!("Board stabilized at {} occupied seats", game.get_count_of_cells_for_state(3));
     game.print_board();
-    println!("Board stabilized at {} occupied seats", game.get_count_of_cells_for_state(3));
+    println!("Board stabilized at {} occupied seats", game.get_count_of_cells_for_state(State::SeatOccupied));
 }
diff --git a/day11/src/rules.rs b/day11/src/rules.rs
new file mode 100644
index 0000000..eb9dcec
--- /dev/null
+++ b/day11/src/rules.rs
@@ -0,0 +1,9 @@
+use enum_map::EnumMap;
+use ndarray::Array2;
+use crate::binary::{Direction, State};
+use crate::board_metadata::{BoardMetadata,CellLocation};
+
+pub trait Rules {
+    fn get_next_state(current_state: State, neighbour_counts: EnumMap<State, usize>) -> State;
+    fn get_neighbours(cell_location: CellLocation, board_metadata: &BoardMetadata, original_states: &Array2<State>) -> EnumMap<Direction, Option<CellLocation>>;
+}
diff --git a/day11/src/rules_easy.rs b/day11/src/rules_easy.rs
new file mode 100644
index 0000000..756b905
--- /dev/null
+++ b/day11/src/rules_easy.rs
@@ -0,0 +1,28 @@
+use enum_map::EnumMap;
+use ndarray::Array2;
+use strum::IntoEnumIterator;
+use crate::binary::{Direction, State};
+use crate::board_metadata::{BoardMetadata,CellLocation};
+use crate::rules::Rules;
+
+pub struct RulesEasy {}
+
+impl Rules for RulesEasy {
+    fn get_next_state(current_state: State, neighbour_counts: EnumMap<State, usize>) -> State {
+        match current_state {
+            State::SeatEmpty => if neighbour_counts[State::SeatOccupied] == 0 { State::SeatOccupied } else { State::SeatEmpty },
+            State::SeatOccupied => if neighbour_counts[State::SeatOccupied] >= 4 { State::SeatEmpty } else { State::SeatOccupied },
+            other => other
+        }
+    }
+
+    fn get_neighbours(cell_location: CellLocation, board_metadata: &BoardMetadata, _original_states: &Array2<State>) -> EnumMap<Direction, Option<CellLocation>> {
+        let mut neighbours = EnumMap::new();
+
+        for direction in Direction::iter() {
+            neighbours[direction] = board_metadata.get_neighbour_location(cell_location, direction);
+        }
+
+        neighbours
+    }
+}