During play press 'I' and then type WINDY followed by Enter. Now type:

Alt-F1	Access all spells
Alt-F2	More mana
Alt-F3	Destroy all players
Alt-F4	Destroy all castles
Alt-F5	Destroy all balloons
Alt-F6	Heal
Alt-F7	Kill all creatures
Alt-F8	More spell experience points
Alt-F9	Free spell usage on/off
Alt-F10	Toggle invincibility on/off
Shift-D	Complete current objective
Shift-C	Complete level