Yooooo thank you for playing and even beating my game haha! I definitely would have wanted to make a more mechanically interesting boss fight, but of course with the extremely tight time limit I had to do what I could! The score is calculated by taking whatever amount of seconds + milliseconds you had left at the end of the level and then multiplying it by 60. The score would accumulate level by level, but dying and restarting resets the score to 0, so in order to get a really good score, you have to beat the whole game without dieing.
I did it that way because I wanted to include a "1 life" mode, but realised it would be way too punishing for the Jam, so I added this system so that when I'm playing the game myself I can have fun doing a score attack with myself haha, my high score as of right now is 1264.56!