apps/frontend/src/MancalaApp.tsx

@@ -14,6 +14,7 @@ import { RTMTWS, ConnectionState, AuthUser } from '@mancala/core';
 import { Theme } from '@mancala/core';
 import LobyPage from './routes/LobyPage';
 import PrivacyPage from './routes/PrivacyPage';
+import RulesPage from './routes/RulesPage';
 import swal from 'sweetalert';
 import Util from './util/Util';
 import { server } from './const/config';
@@ -130,6 +131,7 @@ const MancalaApp: FunctionComponent = () => {
                         </Route>
                         <Route path="privacy" element={<PrivacyPage context={context} theme={theme} userKey={userKey} />}>
                         </Route>
+                        <Route path="rules" element={<RulesPage context={context} theme={theme} />} />
                     </Route>
                 </Routes>
             </BrowserRouter>}

apps/frontend/src/components/Icons.tsx

@@ -71,3 +71,7 @@ export const PauseIcon = ({ size = 22 }: IconProps) => (
 export const BotIcon = ({ size = 20 }: IconProps) => (
     <svg {...stroke(size, 2)}><rect x="4" y="8" width="16" height="12" rx="4" /><path d="M12 4v4" /><circle cx="12" cy="3.5" r="1" /><path d="M9 13v2M15 13v2" /></svg>
 );
+
+export const HelpIcon = ({ size = 20 }: IconProps) => (
+    <svg {...stroke(size, 2)}><circle cx="12" cy="12" r="9" /><path d="M9.5 9.5a2.5 2.5 0 1 1 3.5 2.3c-.7.3-1 .9-1 1.7v.5" /><path d="M12 17.5h.01" /></svg>
+);

apps/frontend/src/components/headerbar/AppHeader.tsx

@@ -4,13 +4,14 @@ import { Link } from "react-router-dom";
 import { AuthUser } from "@mancala/core";
 import { useTranslation } from "react-i18next";
 import { Context } from "../../context/context";
-import { LogoIcon } from "../Icons";
+import { HelpIcon, LogoIcon } from "../Icons";
 import AccountMenu from "./AccountMenu";
 import ThemeSwatches from "./ThemeSwatches";
 
-// The header of every page: logo and name, theme swatches, the account menu when a user is given, and the page's
-// main action (children).
-const AppHeader: FunctionComponent<{ context: Context, authUser?: AuthUser }> = ({ context, authUser, children }) => {
+// The header of every page: logo and name, theme swatches, how to play, the account menu when a user is given, and
+// the page's main action (children). How to play opens the rules page, or calls `onHelp` (the game page shows the
+// rules over the game instead).
+const AppHeader: FunctionComponent<{ context: Context, authUser?: AuthUser, onHelp?: () => void }> = ({ context, authUser, onHelp, children }) => {
     const { t } = useTranslation();
     return (
         <header className={"hdr" + (authUser ? " has-account" : "")}>
@@ -19,6 +20,9 @@ const AppHeader: FunctionComponent<{ context: Context, authUser?: AuthUser }> =
                 <span>{t("Mancala")}</span>
             </Link>
             <ThemeSwatches context={context} />
+            {onHelp
+                ? <button className="btn icon ghost" aria-label={t("HowToPlay")} title={t("HowToPlay")} onClick={onHelp}><HelpIcon /></button>
+                : <Link className="btn icon ghost" to="/rules" aria-label={t("HowToPlay")} title={t("HowToPlay")}><HelpIcon /></Link>}
             {authUser && <AccountMenu context={context} authUser={authUser} />}
             {children}
         </header>

apps/frontend/src/components/home/Home.css

@@ -47,24 +47,10 @@
 .meta .pill { min-width: 0; overflow: hidden; text-overflow: ellipsis; }
 .meta > span:last-child { text-align: right; }
 
-/* Mini board: the top player's store on the left, the bottom player's on the right */
-
-.mini { display: grid; grid-template-columns: 1.15fr repeat(6, minmax(0, 1fr)) 1.15fr; gap: 5px; padding: 8px; border-radius: 16px; background: var(--miniBg); }
-.mini .mp { aspect-ratio: 1; border-radius: 50%; background: var(--miniPit); display: flex; align-items: center; justify-content: center; font-size: 11px; font-weight: 700; color: var(--ink); box-shadow: inset 0 2px 4px rgba(0, 0, 0, .35); }
-.mini .ms { grid-row: 1 / 3; border-radius: 999px; background: var(--miniPit); display: flex; align-items: flex-end; justify-content: center; padding-bottom: 8px; font-size: 13px; font-weight: 800; color: var(--ink); box-shadow: inset 0 2px 4px rgba(0, 0, 0, .35); }
-.mini .ms.l { grid-column: 1; }
-.mini .ms.r { grid-column: 8; color: var(--accent); }
-.mini.lg { gap: 9px; padding: 16px; border-radius: 26px; }
-.mini.lg .mp { font-size: 16px; }
-.mini.lg .ms { font-size: 20px; padding-bottom: 14px; }
-
 @media (max-width: 640px) {
   .hero { grid-template-columns: 1fr; padding: 20px; gap: 20px; border-radius: 26px; }
   .hero h1 { font-size: 25px; }
   .hero .btn { flex: 1; }
-  .mini.lg { gap: 6px; padding: 10px; border-radius: 20px; }
-  .mini.lg .mp { font-size: 13px; }
-  .mini.lg .ms { font-size: 15px; padding-bottom: 10px; }
   .grid { grid-template-columns: 1fr; gap: 14px; }
   .sec { margin: 12px 0 -4px; }
 }

apps/frontend/src/components/home/MiniBoard.css

@@ -0,0 +1,19 @@
+/* Mini board: the top player's store on the left, the bottom player's on the right */
+
+.mini { display: grid; grid-template-columns: 1.15fr repeat(6, minmax(0, 1fr)) 1.15fr; gap: 5px; padding: 8px; border-radius: 16px; background: var(--miniBg); }
+.mini .mp { aspect-ratio: 1; border-radius: 50%; background: var(--miniPit); display: flex; align-items: center; justify-content: center; font-size: 11px; font-weight: 700; color: var(--ink); box-shadow: inset 0 2px 4px rgba(0, 0, 0, .35); }
+.mini .ms { grid-row: 1 / 3; border-radius: 999px; background: var(--miniPit); display: flex; align-items: flex-end; justify-content: center; padding-bottom: 8px; font-size: 13px; font-weight: 800; color: var(--ink); box-shadow: inset 0 2px 4px rgba(0, 0, 0, .35); }
+.mini .ms.l { grid-column: 1; }
+.mini .ms.r { grid-column: 8; color: var(--accent); }
+.mini.lg { gap: 9px; padding: 16px; border-radius: 26px; }
+.mini.lg .mp { font-size: 16px; }
+.mini.lg .ms { font-size: 20px; padding-bottom: 14px; }
+/* A move shown on the board: the pit played and where its last stone landed */
+.mini .played { box-shadow: inset 0 0 0 2px var(--accent); }
+.mini .land, .mini .ms.r.land { background: var(--accent); color: var(--onAccent); }
+
+@media (max-width: 640px) {
+  .mini.lg { gap: 6px; padding: 10px; border-radius: 20px; }
+  .mini.lg .mp { font-size: 13px; }
+  .mini.lg .ms { font-size: 15px; padding-bottom: 10px; }
+}

apps/frontend/src/components/home/MiniBoard.tsx

@@ -1,22 +1,27 @@
 import * as React from "react";
 import { FunctionComponent } from "react";
+import "./MiniBoard.css";
 
 const PLAYER1_PITS = [0, 1, 2, 3, 4, 5];
 const PLAYER2_PITS = [7, 8, 9, 10, 11, 12];
 const PLAYER1_STORE = 6;
 const PLAYER2_STORE = 13;
 
-// Stone counts on a small board, as the bottom player sees it. Empty pits show no number.
-const MiniBoard: FunctionComponent<{ board: number[], revert?: boolean, large?: boolean }> = ({ board, revert, large }) => {
+// Stone counts on a small board, as the bottom player sees it. Empty pits show no number. `played` and `landed` mark
+// a move: the pit played and where its last stone landed.
+const MiniBoard: FunctionComponent<{
+    board: number[], revert?: boolean, large?: boolean, played?: number, landed?: number,
+}> = ({ board, revert, large, played, landed }) => {
     const [topPits, topStore, bottomPits, bottomStore] = revert
         ? [PLAYER1_PITS, PLAYER1_STORE, PLAYER2_PITS, PLAYER2_STORE]
         : [PLAYER2_PITS, PLAYER2_STORE, PLAYER1_PITS, PLAYER1_STORE];
-    const pit = (index: number) => <div key={index} className="mp">{board[index] || ""}</div>;
+    const marks = (index: number) => (index === played ? " played" : "") + (index === landed ? " land" : "");
+    const pit = (index: number) => <div key={index} className={"mp" + marks(index)}>{board[index] || ""}</div>;
     return (
         <div className={"mini" + (large ? " lg" : "")} aria-hidden="true">
-            <div className="ms l">{board[topStore]}</div>
+            <div className={"ms l" + marks(topStore)}>{board[topStore]}</div>
             {[...topPits].reverse().map(pit)}
-            <div className="ms r">{board[bottomStore]}</div>
+            <div className={"ms r" + marks(bottomStore)}>{board[bottomStore]}</div>
             {bottomPits.map(pit)}
         </div>
     );

apps/frontend/src/components/rules/RuleBoard.tsx

@@ -0,0 +1,44 @@
+import * as React from "react";
+import { FunctionComponent } from "react";
+import { getMoveOutcome, RuleExample } from "@mancala/core";
+import MiniBoard from "../home/MiniBoard";
+import { NextIcon } from "../Icons";
+
+// A rule's example: the board before the move with the pit played marked, and after it with the landing pit marked.
+// The board after the move comes from the engine.
+const RuleBoard: FunctionComponent<{ example: RuleExample }> = ({ example }) => {
+    if (example.pitIndex === undefined) {
+        return <div className="rboard single"><MiniBoard board={example.board} /></div>;
+    }
+    const outcome = getMoveOutcome(example.board, example.pitIndex);
+    return (
+        <div className="rboard">
+            <MiniBoard board={example.board} played={example.pitIndex} />
+            <span className="arrow"><NextIcon /></span>
+            <MiniBoard board={outcome.board} landed={outcome.path[outcome.path.length - 1]} />
+            <style jsx>{`
+                .rboard {
+                    display: grid;
+                    grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
+                    align-items: center;
+                    gap: 8px;
+                }
+                .arrow {
+                    color: var(--muted);
+                    display: flex;
+                }
+                @media (max-width: 640px) {
+                    .rboard {
+                        grid-template-columns: minmax(0, 1fr);
+                    }
+                    .arrow {
+                        justify-content: center;
+                        transform: rotate(90deg);
+                    }
+                }
+            `}</style>
+        </div>
+    );
+};
+
+export default RuleBoard;

apps/frontend/src/components/rules/RulesPanel.tsx

@@ -0,0 +1,52 @@
+import * as React from "react";
+import { FunctionComponent } from "react";
+import { useTranslation } from "react-i18next";
+import { CloseIcon } from "../Icons";
+import RulesView from "./RulesView";
+
+// The rules over the game page, so a player can look a rule up without leaving the game (R1.4).
+const RulesPanel: FunctionComponent<{ onClose: () => void }> = ({ onClose }) => {
+    const { t } = useTranslation();
+    return (
+        <div className="rpanel-back" onClick={onClose}>
+            <aside className="rpanel" role="dialog" aria-label={t("HowToPlay")} onClick={(event) => event.stopPropagation()}>
+                <div className="rhead">
+                    <h1>{t("HowToPlay")}</h1>
+                    <button className="btn icon ghost" aria-label={t("Close")} onClick={onClose}><CloseIcon /></button>
+                </div>
+                <RulesView />
+            </aside>
+            <style jsx>{`
+                .rpanel-back {
+                    position: fixed;
+                    inset: 0;
+                    z-index: 50;
+                    background: rgba(0, 0, 0, .45);
+                    display: flex;
+                    justify-content: flex-end;
+                }
+                .rpanel {
+                    width: min(480px, 100%);
+                    height: 100%;
+                    overflow-y: auto;
+                    box-sizing: border-box;
+                    padding: 20px;
+                    background: var(--bg);
+                    box-shadow: -12px 0 30px rgba(0, 0, 0, .3);
+                }
+                .rhead {
+                    display: flex;
+                    align-items: center;
+                    justify-content: space-between;
+                    margin-bottom: 16px;
+                }
+                h1 {
+                    margin: 0;
+                    font-size: 24px;
+                }
+            `}</style>
+        </div>
+    );
+};
+
+export default RulesPanel;

apps/frontend/src/components/rules/RulesView.tsx

@@ -0,0 +1,58 @@
+import * as React from "react";
+import { FunctionComponent } from "react";
+import { Link } from "react-router-dom";
+import { useTranslation } from "react-i18next";
+import { RULES } from "@mancala/core";
+import RuleBoard from "./RuleBoard";
+
+// Every rule in order with its text and example (docs/specs/tutorial, R1). `showLessons` adds a link to each lesson;
+// left out where following it would leave a game.
+const RulesView: FunctionComponent<{ showLessons?: boolean }> = ({ showLessons }) => {
+    const { t } = useTranslation();
+    return (
+        <ol className="rules">
+            {RULES.map((rule) => (
+                <li key={rule.id} id={rule.id} className="rule panel">
+                    <h2>{t(rule.titleKey)}</h2>
+                    {rule.textKeys.map((key) => <p key={key}>{t(key)}</p>)}
+                    {rule.example && <RuleBoard example={rule.example} />}
+                    {showLessons && rule.lesson && (
+                        <Link className="btn ghost try" to={`/learn/${rule.id}`}>{t("TryIt")}</Link>
+                    )}
+                </li>
+            ))}
+            <style jsx>{`
+                .rules {
+                    list-style: none;
+                    margin: 0;
+                    padding: 0;
+                    display: flex;
+                    flex-direction: column;
+                    gap: 16px;
+                }
+                .rule {
+                    padding: 20px;
+                    display: flex;
+                    flex-direction: column;
+                    gap: 10px;
+                }
+                h2 {
+                    margin: 0;
+                    font-size: 20px;
+                    letter-spacing: -.01em;
+                }
+                p {
+                    margin: 0;
+                    color: var(--muted);
+                    line-height: 1.5;
+                }
+                .rules :global(.try) {
+                    align-self: flex-start;
+                    text-decoration: none;
+                }
+            `}</style>
+        </ol>
+    );
+};
+
+export default RulesView;

apps/frontend/src/routes/GamePage.tsx

@@ -28,6 +28,7 @@ import GameClockView from '../components/GameClockView';
 import useGameClock from '../hooks/useGameClock';
 import PlayerCard from '../components/game/PlayerCard';
 import GameOverCard from '../components/game/GameOverCard';
+import RulesPanel from '../components/rules/RulesPanel';
 import '../styles/game.css';
 
 const GamePage: FunctionComponent<{
@@ -61,6 +62,8 @@ const GamePage: FunctionComponent<{
 
     // Set when the server says the game ended, for whatever reason.
     const [gameEnd, setGameEnd] = useState<GameEndMessage | undefined>(undefined);
+    // The rules over the game; the game goes on behind them.
+    const [rulesOpen, setRulesOpen] = useState(false);
 
     // Set when the player closes the game over card to look at the board.
     const [gameOverClosed, setGameOverClosed] = useState<boolean>(false);
@@ -419,11 +422,12 @@ const GamePage: FunctionComponent<{
                 {showBoardView && renderGame()}
                 <LoadingComponent loadingState={gameLoadingState}></LoadingComponent>
             </main>
+            {rulesOpen && <RulesPanel onClose={() => setRulesOpen(false)} />}
         </PageContainer>
     );
 
     function renderHeaderBar() {
-        return <AppHeader context={context}>
+        return <AppHeader context={context} onHelp={() => setRulesOpen(true)}>
             {renderNewGameBtn
                 ? <button className="btn pri ic-m" aria-label={t("NewGame")} onClick={onNewGameClick}>
                     <PlusIcon /><span className="hide-m">{t("NewGame")}</span>

apps/frontend/src/routes/RulesPage.tsx

@@ -0,0 +1,37 @@
+import * as React from "react";
+import { FunctionComponent } from "react";
+import { useTranslation } from "react-i18next";
+import { Theme } from "@mancala/core";
+import AppHeader from "../components/headerbar/AppHeader";
+import PageContainer from "../components/PageContainer";
+import RulesView from "../components/rules/RulesView";
+import { Context } from "../context/context";
+
+// How to play: every rule with an example (docs/specs/tutorial, R1).
+const RulesPage: FunctionComponent<{ context: Context, theme: Theme }> = ({ context }) => {
+    const { t } = useTranslation();
+    return (
+        <PageContainer>
+            <AppHeader context={context} />
+            <main className="wrap rules-page">
+                <h1>{t("HowToPlay")}</h1>
+                <RulesView />
+            </main>
+            <style jsx>{`
+                .rules-page {
+                    max-width: 760px;
+                    width: 100%;
+                    box-sizing: border-box;
+                    align-self: center;
+                }
+                h1 {
+                    margin: 0;
+                    font-size: 30px;
+                    letter-spacing: -.02em;
+                }
+            `}</style>
+        </PageContainer>
+    );
+};
+
+export default RulesPage;

docs/specs/tutorial/tasks.md

@@ -5,7 +5,7 @@ Work through the tasks in order; each ends with its tests passing and a commit.
 - [x] 1. **Spec**: requirements, design and tasks.
 - [x] 2. **Core**: `RULES` with examples and lessons, `getMoveOutcome`, `fulfilsTask`, `explainMove`, `captured` and
       the capture kind in `describeMove`, the storage helpers, texts in English and Turkish; unit tests.
-- [ ] 3. **Rules on the web**: `RuleBoard`, `RulesView`, `/rules`, the help button in `AppHeader`, `RulesPanel` on the
+- [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
       reset, scripted opponent replies.