This is very creative! You know, I actually thought of making a game with typing as a spellcasting mechanic when I was younger (but one of my friends didn’t seem too appealed by it); so I am very excited to see it being implemented here! I enjoyed the game and beat the boss. I think there is a slight dissonance with the controls. I had to either let go of my mouse, or move my left hand across the keyboard to begin a spell, which took away from the flow of action a little bit. I think a better way of handling this would be to assign spells to 1,2,3,4,5 (numbers other other keys) and immediately go into casting when pressed. Even better, forgo the mouse so movement and targeting controls are all keyboard - that would make spellcasting and movement become one and fluid as a baby’s butt. This is possible especially because during spellcasting, the player is not able to move anyway, so that means movement and casting are mutually exclusive, and can exist on the same plane of controls.
For future work, you can add an interesting mechanic where some spells can be typed with only the left hand. For example, words like “red”, “rest” or “water” - these will give a decision-making aspect to the player: go for quick and easy spells to react to something faster, or risk typing longer phrases for devastating effect? I feel this is like casting jutsus with one hand in Naruto, which makes the player feel cool to be able to do it.
Sorry for the long post, it’s because I was excited for the game. I love the levels and concept of this game. I had fun playing it and would love to see it developed even further!