Shoot at the randomly spawning blue brick, don't hit anything that's red. Scores do not carry over between difficulties- for example, if you get 10 points in easy mode, you will not have those same 10 points in normal and hard mode.
easy- one red paddle that doesn't get faster when bricks are hit
normal- one red paddle that gets faster when bricks are hit
hard- 2 alternating red paddles that get faster when bricks are hit