feat(mobile): show the rules

A How to play screen with the same rules and examples as the web app, opened
from the help screen and from the game screen's help button.

apps/mobile/src/App.tsx

@@ -15,6 +15,7 @@ import { NativeModules, I18nManager, Platform } from 'react-native'
 // https://github.com/uuidjs/uuid/issues/514#issuecomment-691475020
 import 'react-native-get-random-values';
 import HelpScreen from './screens/HelpScreen';
+import RulesScreen from './screens/RulesScreen';
 import { getColorByBrightness } from "@mancala/core";
 import { server } from './const/config';
 
@@ -120,6 +121,8 @@ function App() {
           options={{ title: t("Mancala"), headerStyle, headerTintColor }} />
         <Stack.Screen name="Help" component={HelpScreen}
           options={{ title: t("Help"), headerStyle, headerTintColor }} />
+        <Stack.Screen name="Rules" component={RulesScreen}
+          options={{ title: t("HowToPlay"), headerStyle, headerTintColor }} />
       </Stack.Navigator>
     </NavigationContainer>
   );

apps/mobile/src/components/RuleBoard.tsx

@@ -0,0 +1,49 @@
+import * as React from 'react';
+import { FunctionComponent } from 'react';
+import { Text, View } from 'react-native';
+import { getColorByBrightness, getMoveOutcome, RuleExample, Theme } from '@mancala/core';
+
+const TOP_PITS = [12, 11, 10, 9, 8, 7];
+const BOTTOM_PITS = [0, 1, 2, 3, 4, 5];
+
+// Stone counts on a small board as the bottom player sees it; `played` and `landed` mark a move.
+const MiniBoard: FunctionComponent<{ board: number[], theme: Theme, played?: number, landed?: number }> = ({ board, theme, played, landed }) => {
+    const textOn = (color: string) => getColorByBrightness(color, theme.textColor, theme.textLightColor);
+    const cell = (index: number, store: boolean) => {
+        const color = index === landed ? theme.pitSelectedColor : theme.pitColor;
+        return (
+            <View key={index} style={{
+                flex: store ? 1.2 : 1, aspectRatio: store ? undefined : 1, minHeight: store ? undefined : 0,
+                borderRadius: 100, backgroundColor: color, alignItems: 'center', justifyContent: 'center',
+                borderWidth: index === played ? 2 : 0, borderColor: theme.playerTurnColor,
+            }}>
+                <Text style={{ fontSize: 11, fontWeight: '700', color: textOn(color) }}>{board[index] || ''}</Text>
+            </View>
+        );
+    };
+    return (
+        <View style={{ flexDirection: 'row', gap: 4, padding: 6, borderRadius: 12, backgroundColor: theme.boardColor }}>
+            {cell(13, true)}
+            <View style={{ flex: 6, gap: 4 }}>
+                <View style={{ flexDirection: 'row', gap: 4 }}>{TOP_PITS.map((index) => cell(index, false))}</View>
+                <View style={{ flexDirection: 'row', gap: 4 }}>{BOTTOM_PITS.map((index) => cell(index, false))}</View>
+            </View>
+            {cell(6, true)}
+        </View>
+    );
+};
+
+// A rule's example: the board before the move and after it, as the engine plays it.
+const RuleBoard: FunctionComponent<{ example: RuleExample, theme: Theme }> = ({ example, theme }) => {
+    if (example.pitIndex === undefined) return <MiniBoard board={example.board} theme={theme} />;
+    const outcome = getMoveOutcome(example.board, example.pitIndex);
+    return (
+        <View style={{ gap: 6 }}>
+            <MiniBoard board={example.board} theme={theme} played={example.pitIndex} />
+            <Text style={{ textAlign: 'center', color: theme.textColor }}>↓</Text>
+            <MiniBoard board={outcome.board} theme={theme} landed={outcome.path[outcome.path.length - 1]} />
+        </View>
+    );
+};
+
+export default RuleBoard;

apps/mobile/src/screens/GameScreen.tsx

@@ -255,7 +255,7 @@ export function GameScreen({ navigation, route }: GameScreenProps) {
             <CircularPanel color={context.themeManager.theme?.background} children={<Text style={{ color: context.themeManager.theme.textColor }}>{isError ? t('Home') : (isGameEnded ? (!isSpectator && getBotLevel(getOpponentId()) ? t('PlayAgain') : t('NewGame')) : t('Leave'))}</Text>} />
           </Pressable>
           <Pressable onPress={() => {
-            navigation.push("Help", { context })
+            navigation.push("Rules", { context })
           }}>
             <SvgXml xml={helpSvg.replaceAll("customColor", textColorOnAppBar)} width="24" height="24" />
           </Pressable>

apps/mobile/src/screens/HelpScreen.tsx

@@ -31,6 +31,9 @@ export default function HelpScreen({ navigation, route }: HelpScreenProps) {
             alignContent: "center",
             justifyContent: "center"
         }}>
+            <Pressable onPress={() => navigation.push("Rules", { context })}>
+                <Text style={{ textAlign: "center", color: context.themeManager.theme.textColor }}>{t('HowToPlay')}</Text>
+            </Pressable>
             <Pressable onPress={onGotoWebAppClick}>
                 <Text style={{ textAlign: "center", color: context.themeManager.theme.textColor }}>{t('WebApp')}</Text>
             </Pressable>

apps/mobile/src/screens/RulesScreen.tsx

@@ -0,0 +1,26 @@
+import * as React from 'react';
+import { ScrollView, Text, View } from 'react-native';
+import { useTranslation } from 'react-i18next';
+import { RULES } from '@mancala/core';
+import { RulesScreenProps } from '../types';
+import RuleBoard from '../components/RuleBoard';
+
+// How to play: the same rules and examples as the web app (docs/specs/tutorial, R5.1).
+export default function RulesScreen({ route }: RulesScreenProps) {
+    const { context } = route.params;
+    const { t } = useTranslation();
+    const theme = context.themeManager.theme;
+    return (
+        <ScrollView style={{ flex: 1, backgroundColor: theme.background }} contentContainerStyle={{ padding: 16, gap: 24 }}>
+            {RULES.map((rule) => (
+                <View key={rule.id} style={{ gap: 8 }}>
+                    <Text style={{ fontSize: 18, fontWeight: '700', color: theme.textColor }}>{t(rule.titleKey)}</Text>
+                    {rule.textKeys.map((key) => (
+                        <Text key={key} style={{ color: theme.textColor, lineHeight: 20 }}>{t(key)}</Text>
+                    ))}
+                    {rule.example && <RuleBoard example={rule.example} theme={theme} />}
+                </View>
+            ))}
+        </ScrollView>
+    );
+}

apps/mobile/src/types/index.ts

@@ -8,6 +8,7 @@ export type RootStackParamList = {
     Loby: { context: Context, botLevel?: BotLevel },
     Game: { context: Context, gameId: string, userKey: string }
     Help: { context: Context }
+    Rules: { context: Context }
 };
 
 export type HomeScreenProps = NativeStackScreenProps<RootStackParamList, 'Home'>;
@@ -17,3 +18,5 @@ export type LobyScreenProps = NativeStackScreenProps<RootStackParamList, 'Loby'>
 export type GameScreenProps = NativeStackScreenProps<RootStackParamList, 'Game'>;
 
 export type HelpScreenProps = NativeStackScreenProps<RootStackParamList, 'Help'>;
+
+export type RulesScreenProps = NativeStackScreenProps<RootStackParamList, 'Rules'>;

docs/specs/tutorial/tasks.md

@@ -11,6 +11,6 @@ Work through the tasks in order; each ends with its tests passing and a commit.
       reset, scripted opponent replies.
 - [x] 5. **Newcomers and practice game**: `TutorialBanner`, `markGamePlayed`, the practice game button.
 - [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.
+- [x] 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).