Pretty interesting - it's the epitome of quickly-learnable games :-)
Not that much replay value, but, er, there's plenty of entertaining first-play value.
It's very annoying to have to furiously click continuously all the time. Since there's no limit to the speed you can shoot, you're directly encouraged to physically hurt yourself to click faster...
 "Four Second Frenzy"){kind=icon}
 "Bubble Tanks"){kind=icon}