How did Liu Qian's magic change?

I guess: in the process of audience communication! Liu Qian wrote it on paper in some way (maybe on the back, after all, it's a number, you can write it without looking! Just stick a pen in your pants! Writing speed is very fast! The camera can't see it! ) But it must have been written at that time! It's not telepathy. I changed it when I received Dong Qing's red envelope! The problem is probably that Liu Kai's red envelope was taken out with an eye mask when someone opened it, just like the beer in his paper pocket later, as if someone had taken it out with a red envelope when throwing a frisbee. At this time, everyone ignored him. It is likely that he will write it quickly where people are not paying attention, and then pretend to open it with a red envelope. When the audience was in the Frisbee, Liu Qian wrote it down with the paper and pen behind his hand (prepared in advance). Then put it in a finger sleeve (a finger sleeve is a sleeve with props that look like a thumb, and you can put things on your thumb). When opening the envelope, put your thumb in first, then open your finger sleeve and take out the note. The second magic trick: Liu Qian wrote the corresponding patterns on the back of five pieces of paper in advance (for example, the front is round, the back is square, the front is square and the back is+). The back is specially made of chemicals (it has two functions: one is for post-imaging and the other is for light and color recognition). Or Liu Qian uses special contact lenses. As long as you remember the correspondence between the front and the back, you can see which card Dong Qing chose from the back. All he has to do is put the corresponding one back on the top one and drop special ink (chemicals) for a certain period of time, so that a chemical reaction can take place and develop.