diff --git a/src/main.rs b/src/main.rs
index 277c1d7..1d4e7b8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,12 +3,14 @@ mod tile;
 use region::Region;
 
 fn main() {
-	let mut region = Region::new();
+	let mut region = Region::new(1, 1);
+	region.randomise();
 
 	loop {
 		println!("####################");
-		region.print_all();
+		region.print_all(true);
 		region.step();
+		region.auto_grow();
 		{
 			let mut a = String::new();
 			std::io::stdin().read_line(&mut a).unwrap();
diff --git a/src/region.rs b/src/region.rs
index 95960a9..f20ab26 100644
--- a/src/region.rs
+++ b/src/region.rs
@@ -3,25 +3,19 @@ use crate::tile::{Edges, Tile, WIDTH};
 pub struct Region {
 	/// rows of tiles
 	tiles: Vec<Vec<Tile>>,
-	auto_expand: bool,
 }
 
 impl Region {
-	pub fn new() -> Self {
-		let width = 2;
-		let height = 2;
-		let mut tiles = Vec::new();
-		for _ in 0..height {
-			let mut row = Vec::new();
-			for _ in 0..width {
-				row.push(Tile::random());
-			}
-			tiles.push(row);
-		}
+	pub fn new(width: usize, height: usize) -> Self {
+		let tiles = vec![vec![Tile::new(); width]; height];
+		Self { tiles }
+	}
 
-		Self {
-			tiles,
-			auto_expand: false,
+	pub fn randomise(&mut self) {
+		for row in self.tiles.iter_mut() {
+			for tile in row {
+				tile.randomise()
+			}
 		}
 	}
 
@@ -33,23 +27,26 @@ impl Region {
 		self.tiles[0].len()
 	}
 
-	pub fn print_all(&self) {
+	pub fn print_all(&self, tile_grid: bool) {
 		for y in 0..self.height() {
 			for ch_row in 0..(WIDTH / 2) {
 				for x in 0..self.width() {
 					self.tiles[y][x].print_row(ch_row);
-					// print!("|");
+					if tile_grid {
+						print!("|");
+					}
 				}
 				println!()
 			}
-			// println!("------");
+			if tile_grid {
+				println!(
+					"{}",
+					format!("{:->w$}", "+", w = WIDTH + 1).repeat(self.width())
+				);
+			}
 		}
 	}
 
-	// pub fn set_cell(&mut self, x: isize, y: isize, state: bool) {
-	// 	//
-	// }
-
 	fn get_tile_relative(&self, x: usize, y: usize, relx: isize, rely: isize) -> Option<&Tile> {
 		self.tiles
 			.get(y.checked_add_signed(rely)?)
@@ -82,8 +79,33 @@ impl Region {
 				self.tiles[y][x].step(&edges[y][x]);
 			}
 		}
-		if self.auto_expand {
-			// todo
+	}
+
+	pub fn auto_grow(&mut self) {
+		if self.tiles[0].iter().any(|tile| tile.rows[0] != 0) {
+			let row = vec![Tile::new(); self.width()];
+			self.tiles.insert(0, row);
+		}
+		if self.tiles[self.height() - 1]
+			.iter()
+			.any(|tile| tile.rows[WIDTH - 1] != 0)
+		{
+			let row = vec![Tile::new(); self.width()];
+			self.tiles.push(row);
+		}
+		if self.tiles.iter().any(|row| row[0].edge_west() != 0) {
+			for row in &mut self.tiles {
+				row.insert(0, Tile::new());
+			}
+		}
+		if self
+			.tiles
+			.iter()
+			.any(|row| row[row.len() - 1].edge_east() != 0)
+		{
+			for row in &mut self.tiles {
+				row.push(Tile::new());
+			}
 		}
 	}
 }
diff --git a/src/tile.rs b/src/tile.rs
index 33a4dd3..ed6f5c6 100644
--- a/src/tile.rs
+++ b/src/tile.rs
@@ -1,4 +1,4 @@
-pub type Row = u64;
+type Row = u16;
 
 pub const WIDTH: usize = Row::BITS as usize;
 const LAST: usize = WIDTH - 1;
@@ -24,19 +24,29 @@ impl Tile {
 	pub const EMPTY: Tile = Tile { rows: [0; WIDTH] };
 
 	pub fn new() -> Self {
-		Self { rows: [0; WIDTH] }
+		Self::EMPTY
 	}
 
-	pub fn is_empty(&self) -> bool {
-		self.rows.iter().fold(0, |a, r| a | r) == 0
-	}
-
-	pub fn random() -> Self {
-		let mut t = Self::new();
-		for r in 0..(WIDTH / 2) {
-			t.rows[r] = rand::random();
+	pub fn edge_east(&self) -> Row {
+		let mut edge = 0;
+		for n in 0..WIDTH {
+			edge |= (self.rows[n] & 1) << n;
+		}
+		edge
+	}
+
+	pub fn edge_west(&self) -> Row {
+		let mut edge = 0;
+		for n in 0..WIDTH {
+			edge |= (self.rows[n] >> LAST) << n;
+		}
+		edge
+	}
+
+	pub fn randomise(&mut self) {
+		for r in 0..WIDTH {
+			self.rows[r] = rand::random();
 		}
-		t
 	}
 
 	pub fn print_row(&self, ch_row: usize) {
@@ -144,17 +154,11 @@ impl Edges {
 		se: &Tile,
 		sw: &Tile,
 	) -> Self {
-		let mut east = 0;
-		let mut west = 0;
-		for n in 0..WIDTH {
-			east |= (e.rows[n] >> LAST) << n;
-			west |= (w.rows[n] & 1) << n;
-		}
 		Self {
 			n: n.rows[LAST],
 			s: s.rows[0],
-			e: east,
-			w: west,
+			e: e.edge_west(),
+			w: w.edge_east(),
 			nw: (nw.rows[LAST] & 1) != 0,
 			ne: (ne.rows[LAST] >> LAST) != 0,
 			sw: (sw.rows[0] & 1) != 0,