Nicely done, as a whole - good music, nice pixel-art, somewhat addicting gameplay. I'd definitely like to see a bigger version of this.
Some complains, though:
1. Is there a real difference between third and fifth spells? This fireburst seems to be just an upgraded version of lightning, without any caveats.
2. OMG, bless the life-saving table. The gam was so much easier because you could hide behind it and spam fifth spell in most situations. Even flying eyes-type enemies weren't much of a treat there.
3. And, of course, not enough variety - wave 50 was practically the same as wave 10 or wave 30. I suppose this was a more or less conscious choice, of course, but still...
Good work, d00d, keep up!