.projection whiteboard.The black icon below the whiteboard page is to create a blackboard page that meets the teacher's need for different color panel pages. There is a pen below, and the icon of a page is a transparent page. What does a transparent page mean? Just like the meaning of the icon, we chose this function, we will select the current computer screen page, both writing and operating our computer. At the same time we can roam and write handwriting. Maybe a teacher said, what can we do with this transparent page? The teacher likes to play the audio material on the disc. If we use the transparent page function, we can play our audio, and if you want to explain it here, you can write and comment directly here. You can also remove the writing strokes. It is more intuitive to write directly from the audio material than to play the audio on the screen. Looking down, we saw three pens, which are the three simple pen widths we set. The following is the save button, which we will talk about at the end. The black rotating arrow below is the undo button. Undo the previous step. This icon, which is a bit like an eraser, is the eraser equivalent to our blackboard eraser. Touch this icon to click the erase function. We can erase our tiny mistakes little by little. At the same time, under us