Your mission

Professor Tock built a time machine that can REwind, PREview, and UNdo. Then she locked the control panel. A prefix is a small word part stuck on the FRONT of a word, and it changes the meaning. The professor did not leave a list of what the prefixes mean. You know more of them than you think. Use words you already know to work them out.

How to crack a lock

  • Pick any lock from the menu at the top. You can solve them in any order.
  • Read every clue before you start. One clue alone is never enough.
  • Use scratch paper. Draw pictures, make lists, and cross things out.
  • Tap the buttons to build your answer. Then press "Try the lock".
  • A lock will not tell you which part is wrong, so be sure before you try.

My badges

Teacher note

Teachers: type the password to see the answer key.