apps/frontend/src/MancalaApp.tsx

@@ -15,6 +15,8 @@ import { Theme } from '@mancala/core';
 import LobyPage from './routes/LobyPage';
 import PrivacyPage from './routes/PrivacyPage';
 import RulesPage from './routes/RulesPage';
+import LearnPage from './routes/LearnPage';
+import LessonPage from './routes/LessonPage';
 import swal from 'sweetalert';
 import Util from './util/Util';
 import { server } from './const/config';
@@ -132,6 +134,8 @@ const MancalaApp: FunctionComponent = () => {
                         <Route path="privacy" element={<PrivacyPage context={context} theme={theme} userKey={userKey} />}>
                         </Route>
                         <Route path="rules" element={<RulesPage context={context} theme={theme} />} />
+                        <Route path="learn" element={<LearnPage context={context} theme={theme} />} />
+                        <Route path="learn/:ruleId" element={<LessonPage context={context} theme={theme} />} />
                     </Route>
                 </Routes>
             </BrowserRouter>}

apps/frontend/src/routes/LearnPage.tsx

@@ -0,0 +1,94 @@
+import * as React from "react";
+import { FunctionComponent, useEffect } from "react";
+import { Link } from "react-router-dom";
+import { useTranslation } from "react-i18next";
+import { getCompletedLessons, hideTutorialBanner, LESSON_RULES, Theme } from "@mancala/core";
+import AppHeader from "../components/headerbar/AppHeader";
+import PageContainer from "../components/PageContainer";
+import { Context } from "../context/context";
+
+// The lessons in order, the ones done marked (docs/specs/tutorial, R2.6).
+const LearnPage: FunctionComponent<{ context: Context, theme: Theme }> = ({ context }) => {
+    const { t } = useTranslation();
+    useEffect(() => hideTutorialBanner(context.storage), []);
+    const completed = getCompletedLessons(context.storage);
+    return (
+        <PageContainer>
+            <AppHeader context={context} />
+            <main className="wrap learn">
+                <h1>{t("LearnMangala")}</h1>
+                <ol className="lessons">
+                    {LESSON_RULES.map((rule, index) => {
+                        const done = completed.includes(rule.id);
+                        return (
+                            <li key={rule.id}>
+                                <Link className={"lesson-link panel" + (done ? " done" : "")} to={`/learn/${rule.id}`}>
+                                    <span className="num">{done ? "✓" : index + 1}</span>
+                                    <span className="name">{t(rule.titleKey)}</span>
+                                    {done && <span className="pill">{t("LessonDone")}</span>}
+                                </Link>
+                            </li>
+                        );
+                    })}
+                </ol>
+                <Link className="rules-link" to="/rules">{t("HowToPlay")}</Link>
+            </main>
+            <style jsx>{`
+                .learn {
+                    max-width: 760px;
+                    width: 100%;
+                    box-sizing: border-box;
+                    align-self: center;
+                }
+                h1 {
+                    margin: 0;
+                    font-size: 30px;
+                    letter-spacing: -.02em;
+                }
+                .lessons {
+                    list-style: none;
+                    margin: 0;
+                    padding: 0;
+                    display: flex;
+                    flex-direction: column;
+                    gap: 10px;
+                }
+                .learn :global(.lesson-link) {
+                    display: flex;
+                    align-items: center;
+                    gap: 14px;
+                    padding: 14px 18px;
+                    color: var(--ink);
+                    text-decoration: none;
+                    font-weight: 700;
+                }
+                .learn :global(.lesson-link:hover) {
+                    background: var(--surface2);
+                }
+                .learn :global(.num) {
+                    width: 32px;
+                    height: 32px;
+                    flex: none;
+                    border-radius: 50%;
+                    display: flex;
+                    align-items: center;
+                    justify-content: center;
+                    background: var(--surface2);
+                }
+                .learn :global(.done .num) {
+                    background: var(--accent);
+                    color: var(--onAccent);
+                }
+                .learn :global(.name) {
+                    flex: 1;
+                }
+                .learn :global(.rules-link) {
+                    color: var(--muted);
+                    font-weight: 700;
+                }
+            `}</style>
+        </PageContainer>
+    );
+};
+
+export default LearnPage;

apps/frontend/src/routes/LessonPage.tsx

@@ -0,0 +1,201 @@
+import * as React from "react";
+import { FunctionComponent, useEffect, useRef, useState } from "react";
+import { Link, useNavigate, useParams } from "react-router-dom";
+import { useTranslation } from "react-i18next";
+import { v4 } from "uuid";
+import { CommonMancalaGame } from "mancala.js";
+import {
+    BoardViewModel, completeLesson, explainMove, fulfilsTask, Game, getMoveOutcome, getNextLessonRule, getRule,
+    hideTutorialBanner, LESSON_RULES, MoveOutcome, PitAnimator, Theme,
+} from "@mancala/core";
+import AppHeader from "../components/headerbar/AppHeader";
+import PageContainer from "../components/PageContainer";
+import BoardView from "../components/board/BoardView";
+import { Context } from "../context/context";
+
+const YOU = "you";
+const OPPONENT = "opponent";
+
+// A game showing the lesson's board, with the real rules, the player at the bottom to move.
+function createLessonGame(board: number[]): Game {
+    const mancalaGame = new CommonMancalaGame("lesson", YOU, OPPONENT);
+    board.forEach((stoneCount, index) => (mancalaGame.board.pits[index].stoneCount = stoneCount));
+    mancalaGame.turnPlayerId = YOU;
+    mancalaGame.state = "playing";
+    return {
+        id: "lesson",
+        mancalaGame,
+        gameUsersConnectionInfo: {
+            user1ConnectionInfo: { userId: YOU, isOnline: true },
+            user2ConnectionInfo: { userId: OPPONENT, isOnline: true },
+        },
+    };
+}
+
+type Phase = "playing" | "animating" | "done";
+
+// One rule taught on a prepared board (docs/specs/tutorial, R2). Everything runs in the browser on the TypeScript
+// engine; nothing is sent to the server.
+const LessonPage: FunctionComponent<{ context: Context, theme: Theme }> = ({ context }) => {
+    const { t } = useTranslation();
+    const navigate = useNavigate();
+    const { ruleId } = useParams();
+    const rule = getRule(ruleId);
+    const lesson = rule?.lesson;
+    const [game, setGame] = useState<Game | undefined>(undefined);
+    const [boardViewModel, setBoardViewModel] = useState<BoardViewModel | undefined>(undefined);
+    const [phase, setPhase] = useState<Phase>("playing");
+    const [outcome, setOutcome] = useState<MoveOutcome | undefined>(undefined);
+    const [playedIndex, setPlayedIndex] = useState<number | undefined>(undefined);
+    const animator = useRef<PitAnimator | undefined>(undefined);
+    const timer = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
+
+    const start = () => {
+        if (!lesson || !animator.current) return;
+        if (timer.current) clearTimeout(timer.current);
+        const lessonGame = createLessonGame(lesson.board);
+        setGame(lessonGame);
+        setOutcome(undefined);
+        setPhase("playing");
+        animator.current.setNewGame(lessonGame);
+    };
+
+    useEffect(() => {
+        hideTutorialBanner(context.storage);
+        animator.current = new PitAnimator(context.themeManager, (model) => {
+            model.id = v4();
+            setBoardViewModel(model);
+        });
+        start();
+        return () => {
+            if (timer.current) clearTimeout(timer.current);
+            animator.current?.dispose();
+        };
+    }, [ruleId]);
+
+    if (!rule || !lesson) {
+        return (
+            <PageContainer>
+                <AppHeader context={context} />
+                <main className="wrap"><Link to="/learn">{t("AllLessons")}</Link></main>
+            </PageContainer>
+        );
+    }
+
+    const onPitSelect = (index: number) => {
+        if (phase !== "playing" || !game || !(lesson.board[index] > 0) || index > 5) return;
+        const moveOutcome = getMoveOutcome(lesson.board, index);
+        const played = createLessonGame(lesson.board);
+        played.mancalaGame.moveByPlayerPit(YOU, index);
+        setGame(played);
+        setPlayedIndex(index);
+        setPhase("animating");
+        animator.current?.setUpdatedGame(played);
+        const steps = played.mancalaGame.history[0].gameSteps.length;
+        timer.current = setTimeout(() => {
+            setOutcome(moveOutcome);
+            setPhase("done");
+            if (fulfilsTask(lesson.task, moveOutcome)) completeLesson(context.storage, rule.id);
+        }, (steps + 1) * animator.current!.animationInterval);
+    };
+
+    const fulfilled = outcome !== undefined && fulfilsTask(lesson.task, outcome);
+    const next = getNextLessonRule(rule.id);
+    const number = LESSON_RULES.findIndex((r) => r.id === rule.id) + 1;
+
+    return (
+        <PageContainer>
+            <AppHeader context={context} />
+            <main className="wrap lesson">
+                <div className="lhead">
+                    <Link to="/learn" className="crumb">{t("LessonNumber", { number, count: LESSON_RULES.length })}</Link>
+                    <h1>{t(rule.titleKey)}</h1>
+                    {rule.textKeys.map((key) => <p key={key}>{t(key)}</p>)}
+                </div>
+                <div className={"task panel" + (fulfilled ? " ok" : "")} aria-live="polite">
+                    {phase !== "done" && <strong>{t(lesson.taskKey)}</strong>}
+                    {phase === "done" && outcome && (
+                        <>
+                            {fulfilled && <strong>{t("WellDone")}</strong>}
+                            <span>{explainMove(outcome, "you", t)}</span>
+                            <div className="actions">
+                                {fulfilled && next && (
+                                    <button className="btn pri" onClick={() => navigate(`/learn/${next.id}`)}>{t("NextLesson")}</button>
+                                )}
+                                {fulfilled && !next && (
+                                    <button className="btn pri" onClick={() => navigate("/learn")}>{t("AllLessons")}</button>
+                                )}
+                                <button className={"btn " + (fulfilled ? "ghost" : "pri")} onClick={start}>{t("TryAgain")}</button>
+                            </div>
+                        </>
+                    )}
+                </div>
+                {game && boardViewModel && (
+                    <div className="lboard">
+                        <BoardView
+                            game={game}
+                            boardViewModel={boardViewModel}
+                            context={context}
+                            revert={false}
+                            topName={t("Opponent")}
+                            bottomName={t("You")}
+                            onPitSelect={(index) => onPitSelect(index)}
+                            canPlay={phase === "playing"}
+                            lastMoveIndex={phase === "playing" ? undefined : outcome?.pitIndex ?? playedIndex} />
+                    </div>
+                )}
+            </main>
+            <style jsx>{`
+                .lesson {
+                    max-width: 980px;
+                    width: 100%;
+                    box-sizing: border-box;
+                    align-self: center;
+                }
+                .lhead {
+                    display: flex;
+                    flex-direction: column;
+                    gap: 8px;
+                }
+                .lesson :global(.crumb) {
+                    color: var(--muted);
+                    font-weight: 700;
+                    font-size: 14px;
+                    text-decoration: none;
+                }
+                h1 {
+                    margin: 0;
+                    font-size: 28px;
+                    letter-spacing: -.02em;
+                }
+                p {
+                    margin: 0;
+                    color: var(--muted);
+                    line-height: 1.5;
+                }
+                .task {
+                    padding: 16px 20px;
+                    display: flex;
+                    flex-direction: column;
+                    gap: 10px;
+                    flex-shrink: 0;
+                }
+                .task.ok {
+                    box-shadow: inset 0 0 0 2px var(--accent);
+                }
+                .actions {
+                    display: flex;
+                    flex-wrap: wrap;
+                    gap: 10px;
+                }
+                .lboard {
+                    position: relative;
+                    min-width: 0;
+                    flex-shrink: 0;
+                }
+            `}</style>
+        </PageContainer>
+    );
+};
+
+export default LessonPage;

apps/frontend/src/routes/RulesPage.tsx

@@ -1,5 +1,6 @@
 import * as React from "react";
 import { FunctionComponent } from "react";
+import { Link } from "react-router-dom";
 import { useTranslation } from "react-i18next";
 import { Theme } from "@mancala/core";
 import AppHeader from "../components/headerbar/AppHeader";
@@ -14,8 +15,11 @@ const RulesPage: FunctionComponent<{ context: Context, theme: Theme }> = ({ cont
         <PageContainer>
             <AppHeader context={context} />
             <main className="wrap rules-page">
-                <h1>{t("HowToPlay")}</h1>
+                <div className="rtitle">
-                <RulesView />
+                    <h1>{t("HowToPlay")}</h1>
+                    <Link className="btn pri" to="/learn">{t("Lessons")}</Link>
+                </div>
+                <RulesView showLessons />
             </main>
             <style jsx>{`
                 .rules-page {
@@ -24,6 +28,15 @@ const RulesPage: FunctionComponent<{ context: Context, theme: Theme }> = ({ cont
                     box-sizing: border-box;
                     align-self: center;
                 }
+                .rtitle {
+                    display: flex;
+                    align-items: center;
+                    justify-content: space-between;
+                    gap: 12px;
+                }
+                .rules-page :global(.rtitle .btn) {
+                    text-decoration: none;
+                }
                 h1 {
                     margin: 0;
                     font-size: 30px;

docs/specs/tutorial/tasks.md

@@ -7,7 +7,7 @@ Work through the tasks in order; each ends with its tests passing and a commit.
       the capture kind in `describeMove`, the storage helpers, texts in English and Turkish; unit tests.
 - [x] 3. **Rules on the web**: `RuleBoard`, `RulesView`, `/rules`, the help button in `AppHeader`, `RulesPanel` on the
       game page.
-- [ ] 4. **Lessons**: `/learn` with progress, `LessonPage` with the local game, animation, praise, explanation and
+- [x] 4. **Lessons**: `/learn` with progress, `LessonPage` with the local game, animation, praise, explanation and
       reset, scripted opponent replies.
 - [ ] 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`.