Internet censorship in China is nothing new. Most of us are familiar with how the “Great Firewall” blocks certain terms and scrubs “sensitive” images and videos from the web. But those are crude techniques, and censorship in China is becoming ever-more sophisticated.

Just look at the massive protests that have unfolded in Hong Kong over the past couple of weeks. This is a news event that seems like it would give Chinese censors a run for their money: the protests involve millions of people; they are happening in a place that is technically part of China; and online posts about it are written in Chinese. Even so, discussion about it has been almost completely shut down. Searching for “Hong Kong” in China only brings up propaganda, celebrity gossip, and business news.

During the 2014 Umbrella Movement, Hong Kong’s last major protests, Chinese censorship was much more porous. People in China were able to access news about the movement, largely through Instagram. It seems the Chinese government has learned many lessons since then. Watch the video above to learn how this works—technologically, ideologically, and psychologically.

For more videos about China’s role in the world, check out our ongoing series, Because China.