https://youtu.be/RAh4zSt5Uuw?t=1m52sthe general idea is a time-based boss with a steampunk clock-like stage, slowing and speeding up time to trick the player into hitting the attacks
as time changes, the song speed changes. attacks could be throwing gears or something, maybe a musket or flamethrower
after enough damage, phase 2 is entered and the stage transforms into a more modern, electrified stage with lots of lights and electric arcs and lasers and stuff
the time theme keeps up but otherwise the attacks become more challenging lightning attacks
during phase 2, the song changes to
this style although the base melody is the same.