Interesting idea! Giving each wizard a different attack is cool! I think some work on balancing is needed tho.
I think each character's ability should be written somewhere on the character select screen so that players know exactly what they can do. Also having a simple graphic showing the cooldown for the attack would be nice.
Either way, it is a nice simple game that could be expanded with more abilities and characters if you wanted!
Nice job! Keep it up!