When using a mobile device, switching into another window during a study session and then returning to Hack Chinese sometimes causes the page to freeze.

We believe this is because some browsers pause Javascript from running on a page when that page isn't loaded (in order to save CPU cycles and battery). It then has issues restarting Javascript when you return.

If this happens to you, you may have luck pausing your session before switching to another program or using another browser.

If those options do not work, you can just start a new study session.

Don't worry about losing your progress if your study session has frozen; we send all your responses to Hack Chinese as you are studying.