Click on spell buttons, click to place buildings, drag gems to where you need them. Everything can be done with mouse, but there are also some shortcut keys: T – Build tower R – Build trap A – Build amplifier L – Build lightning shrine C – Build charged bolts shrine W – Build wall G – Combine gems B – Throw gem bomb M – Extend mana pool Q – 1x/3x game speed Space – Freeze/unfreeze time N – Send next wave instantly X – Refund mana from gem D – Duplicate gem U – Upgrade gem (duplicate & combine) I – Enable/disable info panels 1,2,3,4,6,7,8,9 – Create gem P or Esc – Go to the Options screen