This is an simple phone projector that does not require to be plugged in an electric outlet,using the principle of using mirror and biconvex lens to magnifying the image on the phone onto the wall.There is a speaker at the end that does not require to be plugged in an electric outlet as well,it's main purpose is to let multiple people to watch videos together.1) use sth.to do 或 use sth.for doing 所以这里的magnifying,不应+ing2) 另外后面一个using在这里应该可以简去3）multiple people意思应该是更多的人吧,用more people更直接.4）应该是let sb.do sth.而不是let sb.to do sth.