I like the idea for this game! Reminds me of Libble Rabble a bit haha. As you continue, you might consider having the boxes fly in from different directions, since at the moment there's no need for the player(s) to move horizontally , as they can dodge just moving up and down.
As some other people mentioned too, some audio feedback for gaining points and losing lives would be helpful, as at first it didn't register to me that my lives were being lost when I collected red cubes.
I also love that it can be enjoyed single player or multiplayer without having to change any settings or gamemodes, it shows how versatile the concept can be! Great job :)