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引导视图
对这一切都陌生？我们会在你学习过程中额外添加通俗易懂的提示和提醒。课程内容完全相同，只是内置了更多辅助说明。
专家视角
You just want the lessons: clean, fast and compact, with no extra reminders. This is the default view.
Questions, corrections, data problems, or takedown requests: send a note and it lands with the operators.
消息仅用于回复，绝不会对外分享。请参阅隐私政策。