diff --git a/src/wordle.zig b/src/wordle.zig
index 901db00..1b40a5a 100644
--- a/src/wordle.zig
+++ b/src/wordle.zig
@@ -9,6 +9,51 @@ pub const Word = [WordLen]u8;
 /// The type of string literals representing words.
 pub const WordLiteral = *const [WordLen:0]u8;
 
+/// The number of rounds in a single Wordle game.
+pub const GameLen = 6;
+
+/// An error reported when a move cannot be played since the game is over.
+pub const GameOver = error{GameOver};
+
+/// A structure for a single Wordle game.
+pub const Game = struct {
+    /// The hidden word to guess.
+    solution: Word,
+
+    /// The round number (starts with 0).
+    round: u32 = 0,
+
+    /// The current (and future) word guesses.
+    ///
+    /// The values of guessBuf[self.round..] are undefined.
+    guessBuf: [GameLen]Word = @splat(@splat(0)),
+
+    /// Fetches the current guesses.
+    pub fn guesses(self: *const Game) []const Word {
+        return self.guessBuf[0..self.round];
+    }
+
+    /// Tests if the game is won.
+    pub fn isWon(self: Game) bool {
+        for (self.guesses()) |guess|
+            if (std.mem.eql(u8, &guess, &self.solution)) return true;
+
+        return false;
+    }
+
+    /// Tests if the game is over.
+    pub fn isOver(self: Game) bool {
+        return self.round >= GameLen or self.isWon();
+    }
+
+    /// Guesses a word unless the game is over.
+    pub fn addGuess(self: *Game, guess: Word) GameOver!void {
+        if (self.isOver()) return error.GameOver;
+        self.guessBuf[self.round] = guess;
+        self.round += 1;
+    }
+};
+
 /// A clue for a spot given a guess.
 pub const Clue = enum {
     Gray,
@@ -98,3 +143,20 @@ test "anagram" {
 test "duplicate letters" {
     try expectGuessClues("fuzzy", "zesty", "  Y G");
 }
+
+test "game" {
+    // default state
+    var game: Game = .{ .solution = strToWord("poise") };
+    try std.testing.expect(!game.isWon());
+    try std.testing.expect(!game.isOver());
+
+    // first guess
+    try game.addGuess(strToWord("brown"));
+    try std.testing.expect(!game.isWon());
+    try std.testing.expect(!game.isOver());
+
+    // second guess
+    try game.addGuess(strToWord("poise"));
+    try std.testing.expect(game.isWon());
+    try std.testing.expect(game.isOver());
+}