Really cool concept. I wish it was more clear what color spell you were using and how much damage you were doing. (Suggestions: A healthbar, and if you make the fireball white with greyscale shading, you can use the "modulate" property to match its color to the element)
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OOOOOhhhhh... I misunderstood what was happening. I was pressing "Q" again to select a spell, instead of space, so I never actually changed spells, which explains why I couldn't hurt some ghosts. Very cool, actually. Maybe just a better indicator that the action is being canceled instead of confirmed.