// === ENGLISH LETTERS AND PETS STORY ===
// Complete English story with Chinese translation and pronunciation

window.ContentModules = window.ContentModules || {};

window.ContentModules.WTA1B1 = {
    id: "wta1b1",
    name: "WTA1B-1",
    description: "English learning story with letters U, V, T and pet vocabulary",
    difficulty: "beginner",
    language: "en-US",
    userLanguage: "zh-CN",
    totalWords: 150,

    // === GRAMMAR LESSONS SYSTEM ===
    grammar: {
        "demonstrative-pronouns": {
            title: "Demonstrative Pronouns - 指示代词",
            explanation: "English uses specific words to point to things that are near or far, singular or plural.",
            rules: [  // Array of simple rule statements
                "this - for one thing that is close",     // Rule 1: Singular + proximity
                "that - for one thing that is far",       // Rule 2: Singular + distance
                "these - for multiple things that are close", // Rule 3: Plural + proximity
                "those - for multiple things that are far"    // Rule 4: Plural + distance
            ],
            examples: [
                {
                    english: "What is this?",        // Source sentence - used in Story Reader, Quiz Game
                    chinese: "这是什么？",             // Translation - displayed in UI, used by Memory Match
                    explanation: "Use 'this' for one thing close to you", // Teaching note - shown in Grammar Discovery
                    pronunciation: "wʌt ɪz ðɪs"      // IPA format - processed by TTS engine
                },
                {
                    english: "What are those?",      // Plural demonstrative question
                    chinese: "那些是什么？",            // Chinese equivalent - cultural context preserved
                    explanation: "Use 'those' for multiple things far from you", // Grammar rule reinforcement
                    pronunciation: "wʌt ɑːr ðoʊz"     // Phonetic guide for pronunciation games
                },
                {
                    english: "These are rabbits.",   // Statement with plural demonstrative
                    chinese: "这些是兔子。",            // Direct translation - maintains sentence structure
                    explanation: "Use 'these' for multiple things close to you", // Pattern explanation
                    pronunciation: "ðiːz ɑːr ræbɪts"  // Sounds for audio-based learning
                },
                {
                    english: "That is my pet bird.",
                    chinese: "那是我的宠物鸟。",
                    explanation: "Use 'that' for one thing far from you",
                    pronunciation: "ðæt ɪz maɪ pet bɜːrd"
                },
                {
                    english: "This cat is very cute.",
                    chinese: "这只猫很可爱。",
                    explanation: "Use 'this' when pointing to something nearby",
                    pronunciation: "ðɪs kæt ɪz veri kjuːt"
                },
                {
                    english: "Are these your turtles?",
                    chinese: "这些是你的乌龟吗？",
                    explanation: "Use 'these' in questions about nearby plural things",
                    pronunciation: "ɑːr ðiːz jʊr tɜːrtəlz"
                },
                {
                    english: "Those dogs are playing.",
                    chinese: "那些狗在玩耍。",
                    explanation: "Use 'those' for distant plural animals or things",
                    pronunciation: "ðoʊz dɔːgz ɑːr pleɪɪŋ"
                },
                {
                    english: "This is my favorite hamster.",
                    chinese: "这是我最喜欢的仓鼠。",
                    explanation: "Use 'this' to introduce something specific and close",
                    pronunciation: "ðɪs ɪz maɪ feɪvərɪt hæmstər"
                }
            ],
            exercises: [
                {
                    type: "fill_blank",
                    sentence: "_____ is a dog.",
                    options: ["This", "These", "That", "Those"],
                    correct: "This",
                    explanation: "Use 'This' for one thing close to you"
                },
                {
                    type: "translation",
                    english: "Those are turtles.",
                    chinese: "那些是海龟。",
                    focus: "Demonstrative pronoun for plural distant objects"
                }
            ]
        },

        "be-verb-usage": {
            title: "Be Verb Usage - Be动词使用",
            explanation: "English 'be' verbs change based on whether you're talking about one thing or many things.",
            rules: [
                "is - used with singular nouns: It is a cat",
                "are - used with plural nouns: They are dogs", 
                "Pattern: This/That + is, These/Those + are"
            ],
            examples: [
                {
                    english: "It is a bird.",
                    chinese: "它是一只鸟。",
                    explanation: "Use 'is' with singular nouns",
                    pronunciation: "ɪt ɪz ə bɜːrd"
                },
                {
                    english: "They are birds.",
                    chinese: "它们是鸟。",
                    explanation: "Use 'are' with plural nouns",
                    pronunciation: "ðeɪ ɑːr bɜːrdz"
                },
                {
                    english: "Where is the cat?",
                    chinese: "猫在哪里？",
                    explanation: "Use 'is' when asking about one thing",
                    pronunciation: "wer ɪz ðə kæt"
                },
                {
                    english: "The dog is happy.",
                    chinese: "狗很高兴。",
                    explanation: "Use 'is' with singular subjects and adjectives",
                    pronunciation: "ðə dɔːg ɪz hæpi"
                },
                {
                    english: "My pets are cute.",
                    chinese: "我的宠物很可爱。",
                    explanation: "Use 'are' with plural nouns like 'pets'",
                    pronunciation: "maɪ pets ɑːr kjuːt"
                },
                {
                    english: "Where are the rabbits?",
                    chinese: "兔子在哪里？",
                    explanation: "Use 'are' when asking about multiple things",
                    pronunciation: "wer ɑːr ðə ræbɪts"
                },
                {
                    english: "This is my turtle.",
                    chinese: "这是我的乌龟。",
                    explanation: "Use 'is' with demonstrative 'this'",
                    pronunciation: "ðɪs ɪz maɪ tɜːrtəl"
                },
                {
                    english: "These are my friends.",
                    chinese: "这些是我的朋友。",
                    explanation: "Use 'are' with demonstrative 'these'",
                    pronunciation: "ðiːz ɑːr maɪ frends"
                }
            ],
            exercises: [
                {
                    type: "fill_blank",
                    sentence: "They ____ turtles.",
                    options: ["is", "are", "am", "be"],
                    correct: "are",
                    explanation: "Use 'are' with plural subjects like 'they'"
                }
            ]
        },

        "prepositions-of-place": {
            title: "Prepositions of Place - 地点介词",
            explanation: "English uses specific words to show where things are located.",
            rules: [
                "on - things touching the top of something: on the chair",
                "in - things inside something: in the box",
                "under - things below something: under the table"
            ],
            examples: [
                {
                    english: "The cat is on the chair.",
                    chinese: "猫在椅子上。",
                    explanation: "Use 'on' when something is touching the top",
                    pronunciation: "ðə kæt ɪz ɑːn ðə tʃer"
                },
                {
                    english: "The turtle is in the water.",
                    chinese: "海龟在水里。",
                    explanation: "Use 'in' when something is inside or surrounded",
                    pronunciation: "ðə tɜːrtəl ɪz ɪn ðə wɔːtər"
                },
                {
                    english: "The dog is under the table.",
                    chinese: "狗在桌子下面。",
                    explanation: "Use 'under' when something is below another thing",
                    pronunciation: "ðə dɔːg ɪz ʌndər ðə teɪbəl"
                },
                {
                    english: "The bird is on the tree.",
                    chinese: "鸟在树上。",
                    explanation: "Use 'on' for things resting on surfaces",
                    pronunciation: "ðə bɜːrd ɪz ɑːn ðə triː"
                },
                {
                    english: "The rabbit is in the garden.",
                    chinese: "兔子在花园里。",
                    explanation: "Use 'in' for enclosed or surrounded spaces",
                    pronunciation: "ðə ræbɪt ɪz ɪn ðə gɑːrdən"
                },
                {
                    english: "The hamster is under the bed.",
                    chinese: "仓鼠在床下面。",
                    explanation: "Use 'under' for things below furniture",
                    pronunciation: "ðə hæmstər ɪz ʌndər ðə bed"
                },
                {
                    english: "My pet is on the sofa.",
                    chinese: "我的宠物在沙发上。",
                    explanation: "Use 'on' when pets sit on furniture",
                    pronunciation: "maɪ pet ɪz ɑːn ðə soʊfə"
                }
            ],
            exercises: [
                {
                    type: "fill_blank",
                    sentence: "The rabbit is ____ the box.",
                    options: ["on", "in", "under", "at"],
                    correct: "in",
                    explanation: "Use 'in' when something is inside a container"
                }
            ]
        },

        "modal-can": {
            title: "Modal Verb 'Can' - 情态动词can",
            explanation: "English uses 'can' to talk about abilities - things someone is able to do.",
            rules: [
                "can + verb (base form) - expresses ability: can sing, can swim",
                "can't = cannot - negative form: can't fly",
                "Can + subject + verb? - question form: Can birds fly?"
            ],
            examples: [
                {
                    english: "She can sing.",
                    chinese: "她会唱歌。",
                    explanation: "Use 'can' + base verb to show ability",
                    pronunciation: "ʃi kæn sɪŋ"
                },
                {
                    english: "I can't find Ding Ding!",
                    chinese: "我找不到丁丁！",
                    explanation: "Use 'can't' for negative ability",
                    pronunciation: "aɪ kænt faɪnd dɪŋ dɪŋ"
                },
                {
                    english: "What can Ding Ding do?",
                    chinese: "丁丁能做什么？",
                    explanation: "Use 'can' in questions about ability",
                    pronunciation: "wʌt kæn dɪŋ dɪŋ du"
                },
                {
                    english: "Dogs can run very fast.",
                    chinese: "狗跑得很快。",
                    explanation: "Use 'can' to describe general abilities",
                    pronunciation: "dɔːgz kæn rʌn veri fæst"
                },
                {
                    english: "Fish can't walk on land.",
                    chinese: "鱼不能在陆地上走路。",
                    explanation: "Use 'can't' for impossible abilities",
                    pronunciation: "fɪʃ kænt wɔːk ɑːn lænd"
                },
                {
                    english: "Can cats climb trees?",
                    chinese: "猫能爬树吗？",
                    explanation: "Use 'Can' at the start of yes/no questions",
                    pronunciation: "kæn kæts klaɪm triːz"
                },
                {
                    english: "Birds can fly in the sky.",
                    chinese: "鸟能在天空中飞行。",
                    explanation: "Use 'can' for natural abilities",
                    pronunciation: "bɜːrdz kæn flaɪ ɪn ðə skaɪ"
                },
                {
                    english: "I can take care of pets.",
                    chinese: "我能照顾宠物。",
                    explanation: "Use 'can' for learned skills",
                    pronunciation: "aɪ kæn teɪk ker ʌv pets"
                },
                {
                    english: "Turtles can't run quickly.",
                    chinese: "乌龟不能跑得很快。",
                    explanation: "Use 'can't' for limited abilities",
                    pronunciation: "tɜːrtəlz kænt rʌn kwɪkli"
                }
            ],
            exercises: [
                {
                    type: "fill_blank",
                    sentence: "Turtles ____ swim.",
                    options: ["can", "can't", "is", "are"],
                    correct: "can",
                    explanation: "Use 'can' to show natural ability"
                }
            ]
        }
    },

    // === LETTERS DISCOVERY SYSTEM ===
    letters: {
        "U": [
            {
                word: "unhappy",                    // Target vocabulary - used in Whack-a-Mole, Word Storm
                translation: "不开心的",             // Chinese meaning - displayed in all translation games
                type: "adjective",                  // Grammar category - used for word type filtering
                pronunciation: "ʌnhæpi",            // Phonetic guide - enables TTS pronunciation
                example: "The cat looks unhappy."  // Usage context - shown in vocabulary explanations
            },
            {
                word: "umbrella",                  // Concrete noun - good for visual memory games
                translation: "雨伞",                 // Common Chinese object - familiar to learners
                type: "noun",                      // Object category - used in noun-focused exercises
                pronunciation: "ʌmbrɛlə",          // Complex pronunciation - practice for advanced learners
                example: "I need an umbrella when it rains." // Real-world usage - context building
            },
            {
                word: "up",                        // Simple directional word - beginner friendly
                translation: "向上",                   // Basic direction concept - easy to visualize
                type: "adverb",                    // Movement modifier - teaches spatial concepts
                pronunciation: "ʌp",                // Short sound - easy pronunciation practice
                example: "The bird flies up high." // Action context - demonstrates usage in motion
            },
            {
                word: "under",                     // Spatial preposition - key for location games
                translation: "在...下面",            // Relational concept - important for grammar
                type: "preposition",               // Connecting word type - links objects and locations
                pronunciation: "ʌndər",            // Clear consonant sounds - good for phonics practice
                example: "The cat hides under the table." // Spatial relationship - concrete scenario
            }
        ],
        "V": [
            {
                word: "violet",
                translation: "紫色的",
                type: "adjective",
                pronunciation: "vaɪələt",
                example: "She has a violet dress."
            },
            {
                word: "van",
                translation: "面包车",
                type: "noun",
                pronunciation: "væn",
                example: "The vet drives a white van."
            },
            {
                word: "vet",
                translation: "兽医",
                type: "noun",
                pronunciation: "vɛt",
                example: "The vet takes care of pets."
            },
            {
                word: "vest",
                translation: "背心",
                type: "noun",
                pronunciation: "vɛst",
                example: "He wears a warm vest."
            }
        ],
        "T": [
            {
                word: "tall",
                translation: "高的",
                type: "adjective",
                pronunciation: "tɔl",
                example: "The teacher is very tall."
            },
            {
                word: "turtle",
                translation: "海龟",
                type: "noun",
                pronunciation: "tɜrtəl",
                example: "The turtle moves slowly."
            },
            {
                word: "tent",
                translation: "帐篷",
                type: "noun",
                pronunciation: "tɛnt",
                example: "We sleep in a tent when camping."
            },
            {
                word: "tiger",
                translation: "老虎",
                type: "noun",
                pronunciation: "taɪgər",
                example: "The tiger is a big cat."
            }
        ]
    },

    vocabulary: {
        "unhappy": {  // Key = English word - used as primary identifier in all games
            "user_language": "不开心的",      // Chinese translation - core data for learning
            "type": "adjective",             // Grammar type - enables filtering by word categories
            "pronunciation": "ʌnhæpi"        // IPA notation - supports audio generation and pronunciation scoring
        },
        "umbrella": {
            "user_language": "雨伞",           // Object name - visual association possible
            "type": "noun",                // Concrete noun - good for memory matching
            "pronunciation": "ʌmbrɛlə"        // Multi-syllable word - pronunciation challenge
        },
        "up": {
            "user_language": "向上",
            "type": "adverb",
            "pronunciation": "ʌp"
        },
        "under": {
            "user_language": "在...下面",
            "type": "preposition", 
            "pronunciation": "ʌndər"
        },
        "uncle": {
            "user_language": "叔叔",
            "type": "noun",
            "pronunciation": "ʌŋkəl"
        },
        "violet": {
            "user_language": "紫色的",
            "type": "adjective",
            "pronunciation": "vaɪələt"
        },
        "van": {
            "user_language": "面包车",
            "type": "noun",
            "pronunciation": "væn"
        },
        "vet": {
            "user_language": "兽医",
            "type": "noun",
            "pronunciation": "vɛt"
        },
        "vest": {
            "user_language": "背心",
            "type": "noun",
            "pronunciation": "vɛst"
        },
        "violin": {
            "user_language": "小提琴",
            "type": "noun",
            "pronunciation": "vaɪəlɪn"
        },
        "tall": {
            "user_language": "高的",
            "type": "adjective",
            "pronunciation": "tɔl"
        },
        "turtle": {
            "user_language": "海龟",
            "type": "noun",
            "pronunciation": "tɜrtəl"
        },
        "tent": {
            "user_language": "帐篷",
            "type": "noun",
            "pronunciation": "tɛnt"
        },
        "tiger": {
            "user_language": "老虎",
            "type": "noun",
            "pronunciation": "taɪgər"
        },
        "teacher": {
            "user_language": "老师",
            "type": "noun",
            "pronunciation": "titʃər"
        },
        "dog": {
            "user_language": "狗",               // Simple animal - universally understood
            "type": "noun",                  // Animal category - used in themed exercises
            "pronunciation": "dɔg"              // Simple pronunciation - beginner-friendly
        },
        "cat": {
            "user_language": "猫",               // Common pet - relatable to children
            "type": "noun",                  // Animal noun - pairs well with dog in exercises
            "pronunciation": "kæt"              // Short vowel sound - phonics practice
        },
        "bird": {
            "user_language": "鸟",
            "type": "noun",
            "pronunciation": "bɜrd"
        },
        "rabbit": {
            "user_language": "兔子",
            "type": "noun",
            "pronunciation": "ræbɪt"
        },
        "hamster": {
            "user_language": "仓鼠",
            "type": "noun",
            "pronunciation": "hæmstər"
        },
        "sofa": {
            "user_language": "沙发",
            "type": "noun",
            "pronunciation": "soʊfə"
        },
        "table": {
            "user_language": "桌子",
            "type": "noun",
            "pronunciation": "teɪbəl"
        },
        "chair": {
            "user_language": "椅子",
            "type": "noun",
            "pronunciation": "tʃɛr"
        },
        "box": {
            "user_language": "盒子",
            "type": "noun",
            "pronunciation": "bɑks"
        },
        "cupboard": {
            "user_language": "橱柜",
            "type": "noun",
            "pronunciation": "kʌbərd"
        },
        "shelf": {
            "user_language": "架子",
            "type": "noun",
            "pronunciation": "ʃɛlf"
        }
    },

    story: {
        title: "The Pet Adventure - 宠物历险记",
        totalSentences: 25,
        chapters: [
            {
                title: "Chapter 1: Choosing a Pet - 第一章：选择宠物",
                sentences: [
                    {
                        id: 1,
                        original: "What is this?",
                        translation: "这是什么？",
                        words: [  // Word-by-word breakdown - enables detailed language analysis
                            {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},  // Question word - starts interrogative pattern
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},      // Be verb - fundamental English grammar
                            {word: "this", translation: "这个", type: "pronoun", pronunciation: "ðɪs"}   // Demonstrative - teaches proximity concept
                        ]
                    },
                    {
                        id: 2,
                        original: "It is a dog.",
                        translation: "这是一只狗。",
                        words: [  // Breakdown shows article usage and noun introduction
                            {word: "It", translation: "它", type: "pronoun", pronunciation: "ɪt"},    // Subject pronoun - sentence structure foundation
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},      // Linking verb - connects subject to object
                            {word: "a", translation: "一只", type: "article", pronunciation: "ə"},     // Indefinite article - introduces countable nouns
                            {word: "dog", translation: "狗", type: "noun", pronunciation: "dɔg"}     // Concrete noun - vocabulary building target
                        ]
                    },
                    {
                        id: 3,
                        original: "What is that?",
                        translation: "那是什么？",
                        words: [
                            {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "that", translation: "那个", type: "pronoun", pronunciation: "ðæt"}
                        ]
                    },
                    {
                        id: 4,
                        original: "It is a hamster.",
                        translation: "它是一只仓鼠。",
                        words: [
                            {word: "It", translation: "它", type: "pronoun", pronunciation: "ɪt"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "a", translation: "一只", type: "article", pronunciation: "ə"},
                            {word: "hamster", translation: "仓鼠", type: "noun", pronunciation: "hæmstər"}
                        ]
                    },
                    {
                        id: 5,
                        original: "What are these?",
                        translation: "这些是什么？",
                        words: [
                            {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},
                            {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                            {word: "these", translation: "这些", type: "pronoun", pronunciation: "ðiz"}
                        ]
                    },
                    {
                        id: 6,
                        original: "They are rabbits.",
                        translation: "它们是兔子。",
                        words: [
                            {word: "They", translation: "它们", type: "pronoun", pronunciation: "ðeɪ"},
                            {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                            {word: "rabbits", translation: "兔子", type: "noun", pronunciation: "ræbɪts"}
                        ]
                    },
                    {
                        id: 7,
                        original: "What are those?",
                        translation: "那些是什么？",
                        words: [
                            {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},
                            {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                            {word: "those", translation: "那些", type: "pronoun", pronunciation: "ðoʊz"}
                        ]
                    },
                    {
                        id: 8,
                        original: "They are turtles.",
                        translation: "它们是海龟。",
                        words: [
                            {word: "They", translation: "它们", type: "pronoun", pronunciation: "ðeɪ"},
                            {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                            {word: "turtles", translation: "海龟", type: "noun", pronunciation: "tɜrtəlz"}
                        ]
                    }
                ]
            },
            {
                title: "Chapter 2: Dora's Pet Ding Ding - 第二章：多拉的宠物丁丁",
                sentences: [
                    {
                        id: 9,
                        original: "It is a new pet for you, Dora.",
                        translation: "多拉，这是给你的新宠物。",
                        words: [
                            {word: "It", translation: "它", type: "pronoun", pronunciation: "ɪt"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "a", translation: "一个", type: "article", pronunciation: "ə"},
                            {word: "new", translation: "新的", type: "adjective", pronunciation: "nu"},
                            {word: "pet", translation: "宠物", type: "noun", pronunciation: "pɛt"},
                            {word: "for", translation: "给", type: "preposition", pronunciation: "fɔr"},
                            {word: "you", translation: "你", type: "pronoun", pronunciation: "ju"},
                            {word: "Dora", translation: "多拉", type: "noun", pronunciation: "dɔrə"}
                        ]
                    },
                    {
                        id: 10,
                        original: "Oh! It is a bird. Thank you very much.",
                        translation: "哦！是一只鸟。非常感谢。",
                        words: [
                            {word: "Oh", translation: "哦", type: "interjection", pronunciation: "oʊ"},
                            {word: "It", translation: "它", type: "pronoun", pronunciation: "ɪt"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "a", translation: "一只", type: "article", pronunciation: "ə"},
                            {word: "bird", translation: "鸟", type: "noun", pronunciation: "bɜrd"},
                            {word: "Thank", translation: "感谢", type: "verb", pronunciation: "θæŋk"},
                            {word: "you", translation: "你", type: "pronoun", pronunciation: "ju"},
                            {word: "very", translation: "非常", type: "adverb", pronunciation: "vɛri"},
                            {word: "much", translation: "多", type: "adverb", pronunciation: "mʌtʃ"}
                        ]
                    },
                    {
                        id: 11,
                        original: "This is my pet Ding Ding. She is a yellow bird. She can sing.",
                        translation: "这是我的宠物丁丁。她是一只黄色的鸟。她会唱歌。",
                        words: [
                            {word: "This", translation: "这", type: "pronoun", pronunciation: "ðɪs"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "my", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                            {word: "pet", translation: "宠物", type: "noun", pronunciation: "pɛt"},
                            {word: "She", translation: "她", type: "pronoun", pronunciation: "ʃi"},
                            {word: "yellow", translation: "黄色的", type: "adjective", pronunciation: "jɛloʊ"},
                            {word: "can", translation: "能", type: "modal", pronunciation: "kæn"},
                            {word: "sing", translation: "唱歌", type: "verb", pronunciation: "sɪŋ"}
                        ]
                    },
                    {
                        id: 12,
                        original: "I can't find Ding Ding!",
                        translation: "我找不到丁丁了！",
                        words: [
                            {word: "I", translation: "我", type: "pronoun", pronunciation: "aɪ"},
                            {word: "can't", translation: "不能", type: "modal", pronunciation: "kænt"},
                            {word: "find", translation: "找到", type: "verb", pronunciation: "faɪnd"}
                        ]
                    },
                    {
                        id: 13,
                        original: "What are those? They are birds. One is yellow. One is blue.",
                        translation: "那些是什么？它们是鸟。一只是黄色的。一只是蓝色的。",
                        words: [
                            {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},
                            {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                            {word: "those", translation: "那些", type: "pronoun", pronunciation: "ðoʊz"},
                            {word: "They", translation: "它们", type: "pronoun", pronunciation: "ðeɪ"},
                            {word: "birds", translation: "鸟", type: "noun", pronunciation: "bɜrdz"},
                            {word: "One", translation: "一只", type: "number", pronunciation: "wʌn"},
                            {word: "yellow", translation: "黄色的", type: "adjective", pronunciation: "jɛloʊ"},
                            {word: "blue", translation: "蓝色的", type: "adjective", pronunciation: "blu"}
                        ]
                    },
                    {
                        id: 14,
                        original: "Now I have two pets!",
                        translation: "现在我有两只宠物了！",
                        words: [
                            {word: "Now", translation: "现在", type: "adverb", pronunciation: "naʊ"},
                            {word: "I", translation: "我", type: "pronoun", pronunciation: "aɪ"},
                            {word: "have", translation: "有", type: "verb", pronunciation: "hæv"},
                            {word: "two", translation: "两", type: "number", pronunciation: "tu"},
                            {word: "pets", translation: "宠物", type: "noun", pronunciation: "pɛts"}
                        ]
                    }
                ]
            },
            {
                title: "Chapter 3: Where Are the Pets? - 第三章：宠物在哪里？",
                sentences: [
                    {
                        id: 15,
                        original: "Where is the cat?",
                        translation: "猫在哪里？",
                        words: [
                            {word: "Where", translation: "哪里", type: "adverb", pronunciation: "wɛr"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "the", translation: "这只", type: "article", pronunciation: "ðə"},
                            {word: "cat", translation: "猫", type: "noun", pronunciation: "kæt"}
                        ]
                    },
                    {
                        id: 16,
                        original: "It is on the chair.",
                        translation: "它在椅子上。",
                        words: [
                            {word: "It", translation: "它", type: "pronoun", pronunciation: "ɪt"},
                            {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                            {word: "on", translation: "在...上", type: "preposition", pronunciation: "ɑn"},
                            {word: "the", translation: "这个", type: "article", pronunciation: "ðə"},
                            {word: "chair", translation: "椅子", type: "noun", pronunciation: "tʃɛr"}
                        ]
                    },
                    {
                        id: 17,
                        original: "Where are the turtles?",
                        translation: "海龟在哪里？",
                        words: [
                            {word: "Where", translation: "哪里", type: "adverb", pronunciation: "wɛr"},
                            {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                            {word: "the", translation: "这些", type: "article", pronunciation: "ðə"},
                            {word: "turtles", translation: "海龟", type: "noun", pronunciation: "tɜrtəlz"}
                        ]
                    }
                ]
            }
        ]
    },

    // === GRAMMAR-BASED FILL IN THE BLANKS ===
    fillInBlanks: [
        {
            sentence: "_____ is a dog.",              // Template with blank - player fills gap
            options: ["This", "These", "That", "Those"],  // Answer choices - shuffled in UI
            correctAnswer: "This",                    // Right answer - validates player selection
            explanation: "Use 'This' for one thing close to you",  // Success message - reinforces rule
            grammarFocus: "demonstrative-pronouns"    // Links to grammar section - enables targeted practice
        },
        {
            sentence: "_____ are turtles.",           // Plural context - tests different demonstrative
            options: ["This", "These", "That", "Those"],  // Same choices - different correct answer
            correctAnswer: "These",                   // Plural demonstrative - teaches number agreement
            explanation: "Use 'These' for multiple things close to you", // Explanation shows plural rule
            grammarFocus: "demonstrative-pronouns"    // Same focus - reinforces pattern
        },
        {
            sentence: "They _____ birds.",            // Subject-verb agreement - core grammar concept
            options: ["is", "are", "am", "be"],       // Be verb options - tests understanding of forms
            correctAnswer: "are",                     // Plural verb - matches plural subject
            explanation: "Use 'are' with plural subjects", // Rule explanation - teaches subject-verb matching
            grammarFocus: "be-verb-usage"             // Different grammar topic - expands coverage
        },
        {
            sentence: "The cat is _____ the chair.",
            options: ["on", "in", "under", "at"],
            correctAnswer: "on",
            explanation: "Use 'on' when something is on top of something else",
            grammarFocus: "prepositions-of-place"
        },
        {
            sentence: "She _____ sing.",
            options: ["can", "can't", "is", "are"],
            correctAnswer: "can",
            explanation: "Use 'can' to show ability",
            grammarFocus: "modal-can"
        },
        {
            sentence: "I _____ find my pet.",
            options: ["can", "can't", "is", "are"],
            correctAnswer: "can't",
            explanation: "Use 'can't' for negative ability",
            grammarFocus: "modal-can"
        }
    ],

    // === GRAMMAR CORRECTION EXERCISES ===
    corrections: [
        {
            incorrect: "This are dogs.",              // Common learner error - number disagreement
            correct: "These are dogs.",               // Corrected version - proper plural form
            explanation: "Use 'These' for multiple things, not 'This'", // Error explanation - teaches rule
            grammarFocus: "demonstrative-pronouns"    // Links to relevant grammar - targeted remediation
        },
        {
            incorrect: "They is cats.",               // Subject-verb mismatch - typical mistake
            correct: "They are cats.",                // Fixed agreement - demonstrates correct pattern
            explanation: "Use 'are' with plural subjects like 'they'", // Teaching point - reinforces rule
            grammarFocus: "be-verb-usage"             // Grammar connection - enables deeper practice
        },
        {
            incorrect: "The bird is in the chair.",   // Preposition confusion - spatial relationship error
            correct: "The bird is on the chair.",     // Spatial correction - proper surface relationship
            explanation: "Use 'on' when something is on top of furniture", // Spatial concept - visual logic
            grammarFocus: "prepositions-of-place"     // Category focus - systematic spatial learning
        },
        {
            incorrect: "She can sings.",
            correct: "She can sing.",
            explanation: "After 'can', use the base form of the verb",
            grammarFocus: "modal-can"
        }
    ],

    // === ADDITIONAL READING STORIES ===
    additionalStories: [
        {
            title: "My Uncle's Pets - 我叔叔的宠物",
            totalSentences: 13,
            chapters: [
                {
                    title: "Chapter 1: The Vet Uncle - 兽医叔叔",
                    sentences: [
                        {
                            id: 1,
                            original: "My uncle is tall.",
                            translation: "我的叔叔很高。",
                            words: [
                                {word: "My", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                                {word: "uncle", translation: "叔叔", type: "noun", pronunciation: "ʌŋkəl"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "tall", translation: "高的", type: "adjective", pronunciation: "tɔl"}
                            ]
                        },
                        {
                            id: 2,
                            original: "He is a vet.",
                            translation: "他是一名兽医。",
                            words: [
                                {word: "He", translation: "他", type: "pronoun", pronunciation: "hi"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "a", translation: "一名", type: "article", pronunciation: "ə"},
                                {word: "vet", translation: "兽医", type: "noun", pronunciation: "vɛt"}
                            ]
                        },
                        {
                            id: 3,
                            original: "He can take care of pets.",
                            translation: "他会照顾宠物。",
                            words: [
                                {word: "He", translation: "他", type: "pronoun", pronunciation: "hi"},
                                {word: "can", translation: "会", type: "modal", pronunciation: "kæn"},
                                {word: "take care", translation: "照顾", type: "verb", pronunciation: "teɪk ker"},
                                {word: "of", translation: "的", type: "preposition", pronunciation: "ʌv"},
                                {word: "pets", translation: "宠物", type: "noun", pronunciation: "pets"}
                            ]
                        },
                        {
                            id: 4,
                            original: "This is his house.",
                            translation: "这是他的房子。",
                            words: [
                                {word: "This", translation: "这", type: "pronoun", pronunciation: "ðɪs"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "his", translation: "他的", type: "pronoun", pronunciation: "hɪz"},
                                {word: "house", translation: "房子", type: "noun", pronunciation: "haʊs"}
                            ]
                        },
                        {
                            id: 5,
                            original: "What are these?",
                            translation: "这些是什么？",
                            words: [
                                {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "these", translation: "这些", type: "pronoun", pronunciation: "ðiːz"}
                            ]
                        },
                        {
                            id: 6,
                            original: "These are his pets.",
                            translation: "这些是他的宠物。",
                            words: [
                                {word: "These", translation: "这些", type: "pronoun", pronunciation: "ðiːz"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "his", translation: "他的", type: "pronoun", pronunciation: "hɪz"},
                                {word: "pets", translation: "宠物", type: "noun", pronunciation: "pets"}
                            ]
                        },
                        {
                            id: 7,
                            original: "That is a dog under the table.",
                            translation: "那是桌子下面的一只狗。",
                            words: [
                                {word: "That", translation: "那", type: "pronoun", pronunciation: "ðæt"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "a", translation: "一只", type: "article", pronunciation: "ə"},
                                {word: "dog", translation: "狗", type: "noun", pronunciation: "dɔg"},
                                {word: "under", translation: "在...下面", type: "preposition", pronunciation: "ʌndər"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "table", translation: "桌子", type: "noun", pronunciation: "teɪbəl"}
                            ]
                        },
                        {
                            id: 8,
                            original: "This cat is on the chair.",
                            translation: "这只猫在椅子上。",
                            words: [
                                {word: "This", translation: "这", type: "pronoun", pronunciation: "ðɪs"},
                                {word: "cat", translation: "猫", type: "noun", pronunciation: "kæt"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "on", translation: "在...上面", type: "preposition", pronunciation: "ɑn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "chair", translation: "椅子", type: "noun", pronunciation: "tʃɛr"}
                            ]
                        },
                        {
                            id: 9,
                            original: "Those rabbits are in the box.",
                            translation: "那些兔子在盒子里。",
                            words: [
                                {word: "Those", translation: "那些", type: "pronoun", pronunciation: "ðoʊz"},
                                {word: "rabbits", translation: "兔子", type: "noun", pronunciation: "ræbɪts"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "in", translation: "在...里面", type: "preposition", pronunciation: "ɪn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "box", translation: "盒子", type: "noun", pronunciation: "bɑks"}
                            ]
                        },
                        {
                            id: 10,
                            original: "The turtle is in the cupboard.",
                            translation: "乌龟在橱柜里。",
                            words: [
                                {word: "The", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "turtle", translation: "乌龟", type: "noun", pronunciation: "tɜrtəl"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "in", translation: "在...里面", type: "preposition", pronunciation: "ɪn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "cupboard", translation: "橱柜", type: "noun", pronunciation: "kʌbərd"}
                            ]
                        },
                        {
                            id: 11,
                            original: "Where is the bird?",
                            translation: "鸟在哪里？",
                            words: [
                                {word: "Where", translation: "哪里", type: "adverb", pronunciation: "wer"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "bird", translation: "鸟", type: "noun", pronunciation: "bɜrd"}
                            ]
                        },
                        {
                            id: 12,
                            original: "The bird is up on the shelf.",
                            translation: "鸟在架子上面。",
                            words: [
                                {word: "The", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "bird", translation: "鸟", type: "noun", pronunciation: "bɜrd"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "up", translation: "向上", type: "adverb", pronunciation: "ʌp"},
                                {word: "on", translation: "在...上面", type: "preposition", pronunciation: "ɑn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "shelf", translation: "架子", type: "noun", pronunciation: "ʃɛlf"}
                            ]
                        },
                        {
                            id: 13,
                            original: "My uncle can help unhappy pets.",
                            translation: "我叔叔能帮助不开心的宠物。",
                            words: [
                                {word: "My", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                                {word: "uncle", translation: "叔叔", type: "noun", pronunciation: "ʌŋkəl"},
                                {word: "can", translation: "能", type: "modal", pronunciation: "kæn"},
                                {word: "help", translation: "帮助", type: "verb", pronunciation: "hɛlp"},
                                {word: "unhappy", translation: "不开心的", type: "adjective", pronunciation: "ʌnhæpi"},
                                {word: "pets", translation: "宠物", type: "noun", pronunciation: "pets"}
                            ]
                        }
                    ]
                }
            ]
        },
        {
            title: "The Violet Van Adventure - 紫色面包车冒险记",
            totalSentences: 15,
            chapters: [
                {
                    title: "Chapter 1: The Magic Van - 神奇的面包车",
                    sentences: [
                        {
                            id: 1,
                            original: "This is a violet van.",
                            translation: "这是一辆紫色的面包车。",
                            words: [
                                {word: "This", translation: "这", type: "pronoun", pronunciation: "ðɪs"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "a", translation: "一辆", type: "article", pronunciation: "ə"},
                                {word: "violet", translation: "紫色的", type: "adjective", pronunciation: "vaɪələt"},
                                {word: "van", translation: "面包车", type: "noun", pronunciation: "væn"}
                            ]
                        },
                        {
                            id: 2,
                            original: "My teacher can drive this van.",
                            translation: "我的老师会开这辆面包车。",
                            words: [
                                {word: "My", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                                {word: "teacher", translation: "老师", type: "noun", pronunciation: "titʃər"},
                                {word: "can", translation: "会", type: "modal", pronunciation: "kæn"},
                                {word: "drive", translation: "开", type: "verb", pronunciation: "draɪv"},
                                {word: "this", translation: "这辆", type: "pronoun", pronunciation: "ðɪs"},
                                {word: "van", translation: "面包车", type: "noun", pronunciation: "væn"}
                            ]
                        },
                        {
                            id: 3,
                            original: "What are those in the van?",
                            translation: "面包车里的那些是什么？",
                            words: [
                                {word: "What", translation: "什么", type: "pronoun", pronunciation: "wʌt"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "those", translation: "那些", type: "pronoun", pronunciation: "ðoʊz"},
                                {word: "in", translation: "在...里面", type: "preposition", pronunciation: "ɪn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "van", translation: "面包车", type: "noun", pronunciation: "væn"}
                            ]
                        },
                        {
                            id: 4,
                            original: "Those are pets!",
                            translation: "那些是宠物！",
                            words: [
                                {word: "Those", translation: "那些", type: "pronoun", pronunciation: "ðoʊz"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "pets", translation: "宠物", type: "noun", pronunciation: "pets"}
                            ]
                        },
                        {
                            id: 5,
                            original: "There is a hamster in a tent.",
                            translation: "有一只仓鼠在帐篷里。",
                            words: [
                                {word: "There", translation: "有", type: "adverb", pronunciation: "ðer"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "a", translation: "一只", type: "article", pronunciation: "ə"},
                                {word: "hamster", translation: "仓鼠", type: "noun", pronunciation: "hæmstər"},
                                {word: "in", translation: "在...里面", type: "preposition", pronunciation: "ɪn"},
                                {word: "a", translation: "一个", type: "article", pronunciation: "ə"},
                                {word: "tent", translation: "帐篷", type: "noun", pronunciation: "tɛnt"}
                            ]
                        },
                        {
                            id: 6,
                            original: "That tiger is tall.",
                            translation: "那只老虎很高。",
                            words: [
                                {word: "That", translation: "那只", type: "pronoun", pronunciation: "ðæt"},
                                {word: "tiger", translation: "老虎", type: "noun", pronunciation: "taɪgər"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "tall", translation: "高的", type: "adjective", pronunciation: "tɔl"}
                            ]
                        },
                        {
                            id: 7,
                            original: "These turtles are under the umbrella.",
                            translation: "这些乌龟在雨伞下面。",
                            words: [
                                {word: "These", translation: "这些", type: "pronoun", pronunciation: "ðiːz"},
                                {word: "turtles", translation: "乌龟", type: "noun", pronunciation: "tɜrtəlz"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "under", translation: "在...下面", type: "preposition", pronunciation: "ʌndər"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "umbrella", translation: "雨伞", type: "noun", pronunciation: "ʌmbrɛlə"}
                            ]
                        },
                        {
                            id: 8,
                            original: "The bird is on the violin.",
                            translation: "鸟在小提琴上。",
                            words: [
                                {word: "The", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "bird", translation: "鸟", type: "noun", pronunciation: "bɜrd"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "on", translation: "在...上面", type: "preposition", pronunciation: "ɑn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "violin", translation: "小提琴", type: "noun", pronunciation: "vaɪəlɪn"}
                            ]
                        },
                        {
                            id: 9,
                            original: "Where are the rabbits?",
                            translation: "兔子在哪里？",
                            words: [
                                {word: "Where", translation: "哪里", type: "adverb", pronunciation: "wer"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "rabbits", translation: "兔子", type: "noun", pronunciation: "ræbɪts"}
                            ]
                        },
                        {
                            id: 10,
                            original: "They are in the violet vest.",
                            translation: "它们在紫色背心里。",
                            words: [
                                {word: "They", translation: "它们", type: "pronoun", pronunciation: "ðeɪ"},
                                {word: "are", translation: "是", type: "verb", pronunciation: "ɑr"},
                                {word: "in", translation: "在...里面", type: "preposition", pronunciation: "ɪn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "violet", translation: "紫色的", type: "adjective", pronunciation: "vaɪələt"},
                                {word: "vest", translation: "背心", type: "noun", pronunciation: "vɛst"}
                            ]
                        },
                        {
                            id: 11,
                            original: "My teacher is unhappy.",
                            translation: "我的老师不开心。",
                            words: [
                                {word: "My", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                                {word: "teacher", translation: "老师", type: "noun", pronunciation: "titʃər"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "unhappy", translation: "不开心的", type: "adjective", pronunciation: "ʌnhæpi"}
                            ]
                        },
                        {
                            id: 12,
                            original: "She can't find her cat.",
                            translation: "她找不到她的猫。",
                            words: [
                                {word: "She", translation: "她", type: "pronoun", pronunciation: "ʃi"},
                                {word: "can't", translation: "不能", type: "modal", pronunciation: "kænt"},
                                {word: "find", translation: "找到", type: "verb", pronunciation: "faɪnd"},
                                {word: "her", translation: "她的", type: "pronoun", pronunciation: "hər"},
                                {word: "cat", translation: "猫", type: "noun", pronunciation: "kæt"}
                            ]
                        },
                        {
                            id: 13,
                            original: "Where is my cat?",
                            translation: "我的猫在哪里？",
                            words: [
                                {word: "Where", translation: "哪里", type: "adverb", pronunciation: "wer"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "my", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                                {word: "cat", translation: "猫", type: "noun", pronunciation: "kæt"}
                            ]
                        },
                        {
                            id: 14,
                            original: "The cat is up on the van!",
                            translation: "猫在面包车上面！",
                            words: [
                                {word: "The", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "cat", translation: "猫", type: "noun", pronunciation: "kæt"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "up", translation: "向上", type: "adverb", pronunciation: "ʌp"},
                                {word: "on", translation: "在...上面", type: "preposition", pronunciation: "ɑn"},
                                {word: "the", translation: "这", type: "article", pronunciation: "ðə"},
                                {word: "van", translation: "面包车", type: "noun", pronunciation: "væn"}
                            ]
                        },
                        {
                            id: 15,
                            original: "Now my teacher is happy.",
                            translation: "现在我的老师开心了。",
                            words: [
                                {word: "Now", translation: "现在", type: "adverb", pronunciation: "naʊ"},
                                {word: "my", translation: "我的", type: "pronoun", pronunciation: "maɪ"},
                                {word: "teacher", translation: "老师", type: "noun", pronunciation: "titʃər"},
                                {word: "is", translation: "是", type: "verb", pronunciation: "ɪz"},
                                {word: "happy", translation: "开心的", type: "adjective", pronunciation: "hæpi"}
                            ]
                        }
                    ]
                }
            ]
        }
    ]
};

// ============================================================================
// CONTENT STRUCTURE SUMMARY - FOR AI REFERENCE
// ============================================================================
//
// REQUIRED SECTIONS (for basic compatibility):
// - vocabulary: Object with word keys, minimum 10 entries
// - Basic metadata: id, name, description, difficulty
//
// RECOMMENDED SECTIONS (for optimal experience):
// - grammar: 2-4 topics with rules and examples
// - story: Main narrative with 15-30 sentences
// - fillInBlanks: 10+ exercises linked to grammar
// - letters: 3+ letters with 3-5 words each
//
// OPTIONAL SECTIONS (for enhanced features):
// - corrections: Error fixing exercises
// - additionalStories: Extended reading material
// - audio: Audio files for pronunciation
// - comprehension: Reading questions
// - matching: Pairing exercises
//
// ============================================================================
// GAME COMPATIBILITY REFERENCE
// ============================================================================
//
// VOCABULARY-BASED GAMES:
// - Whack-a-Mole: Uses vocabulary object directly
// - Memory Match: Pairs words with translations
// - Quiz Game: Multiple choice from vocabulary
// - Word Storm: Falling words game
// - Word Discovery: Letter-by-letter word building
//
// STORY-BASED GAMES:
// - Story Reader: Sequential sentence reading
// - Adventure Reader: RPG-style story navigation
// - Story Builder: User creates stories from vocabulary
//
// GRAMMAR-FOCUSED GAMES:
// - Grammar Discovery: Teaches rules and patterns
// - Fill-the-Blank: Uses fillInBlanks array
// - Chinese Study: Cultural and grammar content
//
// SPECIALIZED GAMES:
// - Letter Discovery: Uses letters object
// - River Run: Vocabulary with time pressure
//
// ============================================================================
// DATA VOLUME GUIDELINES
// ============================================================================
//
// MINIMUM (basic functionality):
// - 10 vocabulary words
// - 1 story chapter (5-8 sentences)
// - 1 grammar topic
//
// OPTIMAL (full experience):
// - 50-100 vocabulary words
// - 3-5 story chapters (20-30 sentences)
// - 3-4 grammar topics with examples
// - 15-20 fill-in-blank exercises
// - 3-5 letters with words
//
// ============================================================================