diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..41776ed
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "tictactoe-rust-foropenspiel"
+version = "0.1.0"
diff --git a/src/game.rs b/src/game.rs
new file mode 100644
index 0000000..2c5d309
--- /dev/null
+++ b/src/game.rs
@@ -0,0 +1,91 @@
+use std::{fmt, str};
+
+// ------------- Player
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Player {
+    Player0,
+    Player1,
+}
+
+impl From<u8> for Player {
+    fn from(item: u8) -> Self {
+        match item {
+            0 => Player::Player0,
+            1 => Player::Player1,
+            _ => Player::Player0,
+        }
+    }
+}
+
+impl From<Player> for u8 {
+    fn from(player: Player) -> u8 {
+        match player {
+            Player::Player0 => 0,
+            Player::Player1 => 1,
+        }
+    }
+}
+
+impl fmt::Display for Player {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let repr = match (self) {
+            Player::Player0 => "x",
+            Player::Player1 => "o",
+        };
+        let mut s = String::new();
+        s.push_str(repr);
+        write!(f, "{s}")
+    }
+}
+
+// ------------- CellState
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CellState {
+    Cross,
+    Nought,
+    Empty,
+}
+
+impl From<Player> for CellState {
+    fn from(player: Player) -> CellState {
+        match player {
+            Player::Player0 => CellState::Cross,
+            Player::Player1 => CellState::Nought,
+        }
+    }
+}
+
+
+impl fmt::Display for CellState {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let repr = match (self) {
+            CellState::Cross => "x",
+            CellState::Nought => "o",
+            CellState::Empty => ".",
+        };
+        let mut s = String::new();
+        s.push_str(repr);
+        write!(f, "{s}")
+    }
+}
+
+// ------------ Board
+
+type Board = Vec<CellState>;
+
+impl Board {
+    fn hasLine(&self, Player player) -> bool {
+        let c: CellState = player.into();
+        (self[0] == c && self[1] == c && self[2] == c) ||
+         (self[3] == c && self[4] == c && self[5] == c) ||
+         (self[6] == c && self[7] == c && self[8] == c) ||
+         (self[0] == c && self[3] == c && self[6] == c) ||
+         (self[1] == c && self[4] == c && self[7] == c) ||
+         (self[2] == c && self[5] == c && self[8] == c) ||
+         (self[0] == c && self[4] == c && self[8] == c) ||
+         (self[2] == c && self[4] == c && self[6] == c);
+    }
+
+}