Breakout's classic paddle has been replaced by a white sphere, controled with the mouse. Hit green blocks to increase your size, although if they contain a skull your sphere will shrink instead. Orange blocks slow down the speed of the ball, and orange skull blocks increase it. Note that breaking the colored blocks is not necessary to clear the level.
While I enjoyed the stripped-down power up system and tasteful, minimal graphics and sound, the levels (which loop at level 9) in Block Kuzusi leave much to be desired. Each features the same 12x3 grid of blocks with only the number and location of the green and orange blocks to differentiate them. Even the original Breakout had more variety than that! Still, Block Kuzusi is one of the better versions Breakout I've seen online, and well worth a look.