Nowadays, smartphone is one of the most popular things in the world. People use smartphone to do a lot of their jobs. It's totally a useful invention but there're some way i need to show if you want to use it effectively. First,don't surf the net too long if you want to harm yourself.It's perfect to use from 30min to 40min because your eyes are sensitive,it can't stand for such a long time. Second,use your smart phone in a good and beneficial purpose. There're a lot of bad people outside so you should beware of them. Last but not least,you have to reduce the usage of your phone so as to be smart and develop your brain. You see,smart phone is not totally a bad idea if we use if well,right?