I'm happy to see a Dragonball game that's not just a fighting game, so I wish I could rate this higher. Unfortunately it's waaay too hard. I lost slowly and painfully on easy mode. This is one that you pretty much have to win right away, because if you slow down even a little your progress is lost pretty much instantly, which makes it frustrating and tiring.

Some improvements (aside from just lowering the difficulty) might be:

 - Break the bar into segments, and make it so that you have to click X amount of dragonballs in Y amount of time to progress 1 segment (moving your kamehameha a little closer to Cell). Then make it a lot harder to lose progress/go backwards a segment than to gain it/go forwards a segment.

- Some sort of visual warning before the dragonballs disappear. I do like that they get smaller, but it's tough to tell exactly when they are small enough that they're going to disappear. You lose a lot of valuable time if you go for dragonballs that disappear before you can click 'em, so some sort of visual flash or color change right before they're set to disappear would help a lot!

- This is more of a personal thing and might not suit what you're going for, but I have a MUCH easier time finding keys on a keyboard than waving my mouse hand around to click all of the places (I occasionally have wrist trouble from Too Much Computer). You could potentially make a version of this game where you press a corresponding key on the keyboard to pop a particular dragonball instead of clicking it with a mouse. Maybe even make it a typing game with lines from the show or manga. Just a thought.

This could be a fun little game with the right tweaks! Best of luck to you!