Fun game, but when the balls come out of the corners suddenly it is not obvious that it's the cause of your failure/loss of life. They should spawn with more fanfare.
Fun game, but my tolerance for 'starting over because you make one mistake' games wanted in the 1990s. A well made game like this will draw you back to complete it at higher difficulty settings if you offer something more, like better power-ups if you choose 'hard mode'.