You move the mouse cursor to move the paddle side to side to defend against various types of balls (5 at the moment). You take damage if the balls reaches the bottom of the screen, and heal 1 hp for every 5 score points you get. The red ball is just basic. The blue ball is slower and deals more damage. The green ball is faster. The yellow ball moves diagonally. The pink ball damages if it goes both below and above the screen, and must be bounced back and forth using a 2nd paddle. The types of balls that can show up each time you click play is random, you may even get no balls or all of them!
This was based on an older game that I've created on a different site, which you can't really access unfortunately (Unless you got the special link from me).