This is a great game and concept.
It's always really fun to craft your own spells, this game was no different. I survived the entiire 15 minutes. And onto the details:
Creativity:
The game fits the theme by an inch. Taking "scaling" in a roguelite sense. The games mechanics are really fun, unfortunetly the game was too easy, i found myself not using haste, teleport or most of the spells, opting to just use ray with all damaging effects. I liked the first and final boss, (though i did one-shot it) The game suffers from poor performance later on due to too many particles.
Art:
The game looks pretty good for one made in 4 days. The art could use some work, but it works and is quite uniform, nothing sticks out. The designs of the bosses are cool. The UI is what bothered me a bit. At the beginning i felt bombarded with information, i feel like Souls and Spirit cancel each other, there is no need for upgrading spells through orbs if they're limited by mana, and vice-versa. The spell making UI was quite bland, and could use a bit of graphics.
Sound:
The game could use a little more soundeffects, it also would be nice for there to be boss music, though the music in the game was pretty good.
Overall great submission, you took 15 minutes of my time and made me enjoy it :)