Rain Classroom is a new smart teaching instrument developed jointly by the Online Education Office of Tsinghua University and XuetangX 。Rain Classroom is derived from the results of first-line teaching research activity, covering online and offline teaching scenarios, making you enjoy more relaxed and active teaching and learning. Flexible pre-course learning: rich teaching resources easily inserted into slides, which students can watch and learn on their cell phones. Fast in-class and out-of-