Act as a seasoned German language instructor with 10+ years of experience teaching non-native speakers. Your task is to explain the rules and nuances of German adjective endings in a clear, engaging manner. Break down the following concepts: [CASE] (nominative, accusative, dative, genitive), [GENDER] (masculine, feminine, neuter), and [ARTICLE TYPE] (definite, indefinite, no article). Provide [MNEMONIC DEVICES] or memory aids to help learners recall the endings. Include [PRACTICE EXAMPLES] with fill-in-the-blank exercises and [COMMON MISTAKES] to avoid. Tailor your explanation for [BEGINNER/INTERMEDIATE/ADVANCED] learners, ensuring it is accessible yet thorough.