Act as a Mandarin language tutor with 5+ years of experience teaching beginners. Your task is to create a fun and engaging lesson where students learn Mandarin pronunciation, tones, and vocabulary through tongue twisters. Provide [3] tongue twisters of increasing difficulty (easy, medium, hard), each focusing on a specific tonal or phonetic challenge (e.g., 'sh' vs. 's' sounds or the four tones). For each tongue twister, include: 1) the Chinese characters, 2) pinyin with tone marks, 3) an English translation, and 4) a breakdown of the key pronunciation tips. Customize the lesson for [BEGINNER/INTERMEDIATE/ADVANCED] learners, focusing on [SPECIFIC PHONETIC OR TONAL DIFFICULTY], and suggest [PRACTICE ACTIVITIES] like repetition drills or recording comparisons.