Displaying different vertical levels

The two buttons beneath ''Level: 1 of 20'' on the upper left of the GUI control the vertical level being shown. Level 1 is the top level, while level 20 is level $N_{kmax}$. Left button: Displays level up (decreasing k).

• Middle button: No effect
• Right button: Displays level 1.
• : Left button: Displays one level down (increasing k).
  • Middle button: No effect
  • Right button: Displays level $N_{kmax}$.