Nice setting on the story of your game! Judging from the map, I'm assuming you plan to have previously inaccessible areas, and with more mechanics unlocked, they can return to them later? It's a 100%'ers dream! One thing I noticed is that the first boss's attack pattern have different executing times(the triple vertical cannons vs the 3 front & back cannons)?
If that's intended, then probably it'll be best to have an indicator showing when they are about to fire to easily keep track of both timers when punishing the boss. Good job on submitting your game this jam!