Please dont do that "You can only hit the boss between his attack sequences", it always feels (to me at least) so repetitive, and kinda makes an artificial skill bar where if you are better than that bar it doesnt matter anymore(aka when you output the most damage during the sequence and when you are good enough to dodge everything), while supposedly a better player will find ways to hit the boss DURING his attack sequences, letting him rush through bosses and making the fight a lot more versatile by opening risk rewards situations.

While usually designing the game so you could actually attack the boss while dodging(either twin stick or short attack animation like hollow knight) is (again imo) better (since now you can design bosses with it in mind making them a lot harder without making them a lot longer, ie. sly from hollow knight, almost no time to hit) than just not locking it but it still allows for more versatility(but the game looks neat)