The game is fun to control and move around in, I will say. As a suggestion, maybe the timer could be shorter so we can easily swap between each character and continue at a fixed pace instead of waiting. Bowser's Fury is a similar concept, with Fury Bowser coming out every so often to attack, and you can use his attacks to find more shines. If you have an Amiibo, you can summon Bowser at will. I thought of this game while playing and it seems like a good place to take inspiration from if you ever intend to continue working on the game.