feat(frontend): show hints in games against the bot

With hints on, the player's pits show whether their move gives an extra turn
or how many stones it takes, and a line under the board says what the last
move did and why. A Hints switch appears only in games against the bot.

apps/frontend/src/components/board/BoardView.css

@@ -165,6 +165,28 @@
   pointer-events: none;
 }
 
+.hintchip {
+  position: absolute;
+  left: 50%;
+  top: -10px;
+  transform: translateX(-50%);
+  max-width: 120%;
+  padding: 2px 8px;
+  box-sizing: border-box;
+  border-radius: 10px;
+  background: var(--surface2);
+  color: var(--accent);
+  box-shadow: inset 0 0 0 1.5px var(--accent);
+  font-weight: 800;
+  font-size: 11px;
+  line-height: 16px;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  z-index: 3;
+  pointer-events: none;
+}
+
 @container (max-width: 600px) {
   .board {
     --pw: min(170px, calc((100cqw - 70px) / 2));

apps/frontend/src/components/board/BoardView.tsx

@@ -27,7 +27,9 @@ const BoardView: FunctionComponent<{
   lastMoveIndex?: number;
   // Board index where the shown move's last stone landed.
   landIndex?: number;
-}> = ({ game, context, boardViewModel, revert, topName, bottomName, onPitSelect, canPlay, lastMoveIndex, landIndex }) => {
+  // What the bottom player's moves would do, by board index (hints in games against the bot).
+  hints?: Record<number, string>;
+}> = ({ game, context, boardViewModel, revert, topName, bottomName, onPitSelect, canPlay, lastMoveIndex, landIndex, hints }) => {
   const { t } = useTranslation();
   const [previewIndex, setPreviewIndex] = useState<number | undefined>(undefined);
   const board = game.mancalaGame.board;
@@ -45,6 +47,7 @@ const BoardView: FunctionComponent<{
     preview: preview[index],
     land: previewLand !== undefined ? index === previewLand : index === landIndex,
     last: index === lastMoveIndex,
+    hint: hints?.[index],
   });
 
   const topPits = revert ? board.player1Pits : board.player2Pits;

apps/frontend/src/components/board/PitView.tsx

@@ -11,6 +11,8 @@ export type PitMarks = {
   land?: boolean;
   // The last move was played from here.
   last?: boolean;
+  // What playing this pit would do, in games against the bot with hints on, e.g. "Extra turn".
+  hint?: string;
 };
 
 export function getMarkClasses(marks: PitMarks): string {
@@ -47,6 +49,7 @@ const PitView: FunctionComponent<{
       <Stones count={stoneCount} seed={index * 5.3 + 1} themeId={themeId} />
       <span className={top ? "badge t" : "badge b"}>{stoneCount}</span>
       {!!marks.preview && <span className="pvchip">{`+${marks.preview}`}</span>}
+      {!!marks.hint && <span className="hintchip">{marks.hint}</span>}
     </>
   );
   if (!onClick) {

apps/frontend/src/routes/GamePage.tsx

@@ -9,7 +9,7 @@ import LoadingComponent from '../components/LoadingComponent';
 import PageContainer from '../components/PageContainer';
 import AppHeader from '../components/headerbar/AppHeader';
 import { LeaveIcon, PlusIcon } from '../components/Icons';
-import { GameRecord, channel_on_game_update, channel_on_game_crashed, channel_on_game_end, channel_on_game_user_leave, channel_on_user_connection_change, channel_leave_game, channel_game_move, channel_listen_game_events, channel_unlisten_game_events, FinishedGameSummary, GameEndMessage, getBoardAfterMove, getSeat, PlayedMove } from '@mancala/core';
+import { GameRecord, channel_on_game_update, channel_on_game_crashed, channel_on_game_end, channel_on_game_user_leave, channel_on_user_connection_change, channel_leave_game, channel_game_move, channel_listen_game_events, channel_unlisten_game_events, FinishedGameSummary, GameEndMessage, getBoardAfterMove, getSeat, PlayedMove, getHintsEnabled, setHintsEnabled, getMoveOutcome, explainMove } from '@mancala/core';
 import { Context } from '../context/context';
 import { GameMove, LoadingState, Game, GameUsersConnectionInfo } from "@mancala/core";
 import { Theme, getBotLevel, getPlayerDisplayName } from '@mancala/core';
@@ -64,6 +64,8 @@ const GamePage: FunctionComponent<{
     const [gameEnd, setGameEnd] = useState<GameEndMessage | undefined>(undefined);
     // The rules over the game; the game goes on behind them.
     const [rulesOpen, setRulesOpen] = useState(false);
+    // Hints in games against the bot (docs/specs/tutorial, R3); remembered on the device.
+    const [hintsEnabled, setHintsEnabledState] = useState(() => getHintsEnabled(context.storage));
 
     // Set when the player closes the game over card to look at the board.
     const [gameOverClosed, setGameOverClosed] = useState<boolean>(false);
@@ -278,6 +280,34 @@ const GamePage: FunctionComponent<{
 
     const moves = (mancalaGame?.history ?? []) as unknown as PlayedMove[];
     const isReviewing = viewedMove !== undefined && viewedMove < moves.length;
+
+    // Hints are only for games against the bot, never between people (R3.5).
+    const hintsOn = !!opponentBotLevel && hintsEnabled;
+    const toggleHints = () => {
+        setHintsEnabled(context.storage, !hintsEnabled);
+        setHintsEnabledState(!hintsEnabled);
+    };
+    const getHints = (): Record<number, string> | undefined => {
+        if (!hintsOn || !mancalaGame || isReviewing || hasOngoingAction) return undefined;
+        if (mancalaGame.turnPlayerId !== userKey || mancalaGame.state === "ended") return undefined;
+        const stones = mancalaGame.board.getStoneArray();
+        const first = isPlayer2 ? 7 : 0;
+        const hints: Record<number, string> = {};
+        for (let index = first; index < first + 6; index++) {
+            if (!stones[index]) continue;
+            const outcome = getMoveOutcome(stones, index);
+            if (outcome.capture) hints[index] = t("HintCaptures", { count: outcome.captured });
+            else if (outcome.extraTurn) hints[index] = t("HintExtraTurn");
+        }
+        return hints;
+    };
+    // What the last move did and why, under the board (R3.3).
+    const getLastMoveExplanation = (): string | undefined => {
+        if (!hintsOn || moves.length === 0 || isReviewing) return undefined;
+        const last = moves[moves.length - 1];
+        const outcome = getMoveOutcome(getBoardAfterMove(moves, moves.length - 1), last.moveIndex);
+        return explainMove(outcome, last.playerId === userKey ? "you" : "bot", t);
+    };
     const shownBoardViewModel = isReviewing && mancalaGame
         ? createBoardViewModel(getBoardAfterMove(moves, viewedMove!), context.themeManager.theme)
         : boardViewModel;
@@ -351,6 +381,7 @@ const GamePage: FunctionComponent<{
 
     const renderGame = () => {
         const board = mancalaGame!.board;
+        const lastMoveExplanation = getLastMoveExplanation();
         const [topStore, bottomStore] = isPlayer2
             ? [board.player1BankIndex(), board.player2BankIndex()]
             : [board.player2BankIndex(), board.player1BankIndex()];
@@ -373,6 +404,11 @@ const GamePage: FunctionComponent<{
                         {!isGameOver && <span className="dot" />}
                         {getTurnText()}
                     </div>
+                    {opponentBotLevel && (
+                        <button className={"btn hints-toggle " + (hintsOn ? "pri" : "ghost")} aria-pressed={hintsOn} onClick={toggleHints}>
+                            {t("Hints")}
+                        </button>
+                    )}
                 </div>
                 <div className="a-me">{playerCard(bottomLocatedUser, bottomStore, isSpectator ? "" : t("You"), true)}</div>
                 <div className="a-board">
@@ -391,7 +427,9 @@ const GamePage: FunctionComponent<{
                         lastMoveIndex={moves[(isReviewing ? viewedMove! : moves.length) - 1]?.moveIndex}
                         topName={topLocatedUser.name}
                         bottomName={bottomLocatedUser.name}
-                        revert={isPlayer2} />
+                        revert={isPlayer2}
+                        hints={getHints()} />
+                    {lastMoveExplanation && <p className="hint-line" aria-live="polite">{lastMoveExplanation}</p>}
                     {isGameOver && !gameOverClosed && (
                         <GameOverCard
                             title={resultTitle ?? t("GameEnded")}

apps/frontend/src/styles/game.css

@@ -10,7 +10,7 @@
 }
 
 .a-opp { grid-area: opp; min-width: 0; }
-.a-turn { grid-area: turn; min-width: 0; }
+.a-turn { grid-area: turn; min-width: 0; display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 8px; }
 .a-me { grid-area: me; justify-self: end; min-width: 0; }
 .a-board { grid-area: board; position: relative; min-width: 0; }
 .a-moves { grid-area: moves; width: 100%; max-width: 760px; justify-self: center; display: flex; flex-direction: column; gap: 16px; }
@@ -100,6 +100,11 @@
 
 .turn.mine { background: var(--accent); color: var(--onAccent); box-shadow: none; }
 
+/* Hints in games against the bot */
+
+.hints-toggle { min-height: 36px; padding: 0 14px; font-size: 14px; }
+.hint-line { margin: 14px 0 0; text-align: center; color: var(--muted); font-weight: 600; line-height: 1.45; }
+
 /* Review banner, above the board */
 
 .review {

docs/specs/tutorial/design.md

@@ -123,8 +123,9 @@ Components:
   `explainMove` and "Try again", which resets the board.
 - `TutorialBanner` on the home page for newcomers (R4).
 - Hints (R3): in `GamePage`, when the opponent is a bot and hints are on, `BoardView` gets a `hints` map
-  (pit → "Extra turn" / "Captures 5"), drawn as a chip on the pit like the move preview; below the board a line with
+  (pit → "Extra turn" / "Takes 5"), drawn as a chip above the pit; pits whose move does neither get no chip. Below
-  `explainMove` of the last move. A "Hints" switch in the game page's toolbar, only in bot games.
+  the board a line with `explainMove` of the last move. A "Hints" switch next to the turn indicator, only in bot
+  games; hidden while looking back at earlier moves.
 - Practice game: the lesson list's last button sets hints on and goes to `/loby?bot=easy`.
 
 ## Mobile app

docs/specs/tutorial/tasks.md

@@ -10,7 +10,7 @@ Work through the tasks in order; each ends with its tests passing and a commit.
 - [x] 4. **Lessons**: `/learn` with progress, `LessonPage` with the local game, animation, praise, explanation and
       reset, scripted opponent replies.
 - [x] 5. **Newcomers and practice game**: `TutorialBanner`, `markGamePlayed`, the practice game button.
-- [ ] 6. **Hints**: hint chips on `BoardView`, the explanation line and the "Hints" switch in bot games on `GamePage`.
+- [x] 6. **Hints**: hint chips on `BoardView`, the explanation line and the "Hints" switch in bot games on `GamePage`.
 - [ ] 7. **Mobile rules**: `RulesScreen`, links from the help and game screens; type check and bundle.
 - [ ] 8. **End to end and docs**: the Chrome tests from `design.md`; `AGENTS.md` (specs list), `TODO.md` (out of scope
       items).