This is a Good game for a first your first published game and first game jam, however there is a couple of things that can be changed, such as the shop. The shop itself is very unnecessary in terms of presentation, a way this can be changed is by diving up bosses with mini bosses and shops after defeating The Boss of the level.
Also good job in terms of the game itself, it works well and smoothly for what has to offer. Keep trying and keep putting effort into it.