Use WASD or the Arrow Keys to move and jump. Press S, Down or E to enter doors, or to start a level from the world map. Find a way to reach the white flag in each level! But remember, not everything is always as it seems.

TIP: GUI means Graphical User Interface, which refers to all the buttons on the screen. Sometimes these buttons might have special functions that you aren't expecting. Try clicking around on different buttons and see if you can come up with a new idea!