This game does indeed fit the theme very well.
Perhaps a bit too well, as it's incredibly hard to rack up a high score since you have so little control over anything other that movement and when to shoot.
Maybe adding in a few extra mechanics to the game such as semi-random aiming (i.e. you can choose roughly which direction to shoot, but the spell bends into a slightly skewed direction), or a wider level to explore so that the player isn't as prone to their spell bouncing back into them when they are anywhere near a wall.
Apart from that the idea is solid and could definitely prove to be a fun timesink with more variety to the gameplay!