Really cool game. The concept is creative and seems well thought out. It's particularly clever how stronger spells have longer words so they're both harder to make and take longer to charge. The letters you get seem well balanced in that you get enough letters to make some spells, but not all of them, so you need to pick and choose what the letters go to. The graphics look great and the music is nice to listen to.
My minor nit-pick is that it's annoying having to re-equip spells constantly. The last spell you used should stay selected.