Nice little demo. Without checkpoints of some sort it was way to difficult for me to complete it since each time you die you have to slog through the previous section and the enemy variety is lacking.
I am wondering if there is some way to block the miniboss attacks? Overall you just need more content and mechanics. More varied ways to interact with the world via spellings.
I like the spell idea for example, but I really dont find any reason to use it, as it wasnt effective in bursting down the mini boss.
Just add more enemy types with different spelling schemes. I'm sure you know of it, but Typer Shark Deluxe is a good game to look at for this sort of gameplay. You should at least have everything typer shark had+more.
Heres my gameplay vid: