BPM can be a bit hard at the beginning so here is a few tips:
- Your starting weapon can shoot on full and half beats.
- If your weapon gets locked stop spamming.
- You can jump on half beats aswell for a double jump.
Though most importantly you need to get a feel for the music and the beat and you are only going to obtain that by playing.
Lifehack: If you are currently not in combat hold LSHIFT to run which is a bit faster than dashing all the time and good for backtracking.
To get into the library you require a key. Once inside you will gain an active Ability on your E, some of them need charging time some of them do not.
Side bosses are smaller bosses that are usually quite easy compared to the rest of the rooms. You can focus on just one target which is nice.
The first boss is not that difficult once you figure out his pattern. Though I highly recommend you figure it out on your own because that is the most satisfying thing to learn about this game.