Currently, there is no mouse support, so you have to do everything via keystrokes.
ESC - switches text display on and off
F1 - switches between output window and editor window and off state
F2 - switches between editor window and off state
F4 - stops program that is currently running
Ctrl-Pause (Break) - stops program that is currently running
Ctrl-C - stops program that is currently running
Alt-F4 - terminates THE ENGINE
Arrow Keys - move the text cursor
Home/End - go beginning of line or screen, or end of line or screen
Ins/Del - insert/delete characters
Backspace - delete backwards
Ctrl-Home - clear screen and put cursor in home position
Ctrl-End - clear screen and put cursor in end position
PageUp/Dn - browse history (Output window) or text (Editor)