Hmm... I'm not quite sure what you mean by the invisible enemies. There's 3 main enemy types, There's the one that moves towards the paddles, there's one that spins and shoots a bullet to the right every time it completes a circle, and there's an enemy that spawns on the left that shoots two bullets on both of the diagonal left angles whenever it gets big. If I had to guess, I'd think that you're talking about the diagonal shooting ones because they shoot really fast.
The thing with the mouse controls is something I might do, but I fear that it might make the game too easy where you literally just put the mouse over an enemy and then dodge until the enemy is dead while keeping the ball alive.