diff --git a/Cargo.toml b/Cargo.toml
index a6f1e9d..09ccdf3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rand = "0.8.5"
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..0c9db93
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,122 @@
+use std::{collections::HashSet, fmt::{Display, Write}};
+
+use rand::Rng;
+
+pub type Position = (usize, usize);
+
+#[derive(Debug)]
+pub struct Minesweeper {
+	width: usize,
+	height: usize,
+	open_fields: HashSet<Position>,
+	mines: HashSet<Position>,
+	flags: HashSet<Position>,
+}
+
+impl Display for Minesweeper {
+	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+		for y in 0..self.height {
+			for x in 0..self.height {
+				let pos = (x, y);
+				if self.flags.contains(&pos) {
+					f.write_str("F ")?;
+				} else if !self.open_fields.contains(&pos) {
+					f.write_str("# ")?;
+				} else if self.mines.contains(&pos) {
+					f.write_str("B ")?;
+				} else {
+					write!(f, "{} ", self.count_mines(pos))?;
+				}
+			}
+			f.write_char('\n')?;
+		}
+
+		Ok(())
+	}
+}
+
+pub enum OpenResult {
+	Mine,
+	NoMine(u8)
+}
+
+impl Minesweeper {
+	pub fn new(width: usize, height: usize, mine_count: usize) -> Minesweeper {
+		Minesweeper {
+			width,
+			height,
+			open_fields: HashSet::new(),
+			mines: generate_mines(width, height, mine_count),
+			flags: HashSet::new(),
+		}
+	}
+
+	pub fn iter_neighbours(&self, (x, y): Position) -> impl Iterator<Item = Position> {
+		let width = self.width;
+		let height = self.height;
+
+		(x.max(1) - 1 ..= (x + 1).min(width - 1)).flat_map(
+			move |i| (y.max(1) - 1 ..= (y + 1).min(height - 1)).map(move |j| (i, j))
+		).filter(move |&pos| pos != (x, y))
+	}
+
+	pub fn count_mines(&self, position: Position) -> u8 {
+		self.iter_neighbours(position)
+			.filter(|pos| self.mines.contains(pos))
+			.count() as u8
+	}
+
+	pub fn open(&mut self, position: Position) -> Option<OpenResult> {
+		if self.flags.contains(&position) {
+			return None;
+		}
+
+		self.open_fields.insert(position);
+		let is_mine = self.mines.contains(&position);
+		if is_mine {
+			Some(OpenResult::Mine)
+		} else {
+			Some(OpenResult::NoMine(0))
+		}
+	}
+
+	pub fn toggle_flag(&mut self, position: Position) {
+		if self.open_fields.contains(&position) {
+			return;
+		}
+
+		if self.flags.contains(&position) {
+			self.flags.remove(&position);
+		} else {
+			self.flags.insert(position);
+		}
+	}
+}
+
+fn generate_mines(field_width: usize, field_height: usize, mine_count: usize) -> HashSet<Position> {
+	let mut mines = HashSet::new();
+
+	let mut rng = rand::thread_rng();
+	while mines.len() < mine_count {
+		let x = rng.gen_range(0..field_width);
+		let y = rng.gen_range(0..field_height);
+		mines.insert((x, y));
+	}
+
+	mines
+}
+
+#[cfg(test)]
+mod tests {
+	use crate::Minesweeper;
+
+	#[test]
+	fn test() {
+		let mut ms = Minesweeper::new(5, 5, 5);
+
+		ms.open((2, 2));
+		ms.toggle_flag((3, 3));
+
+		println!("{}", ms);
+	}
+}