Infinigon

In Infinigon you start as a simple line, and by catching balls with the white line of your shape, you gain points and slowly grow into bigger more complicated shapes.
The further you get, the harder it becomes to keep up. There are random events where you'll be zoomed in, making it harder to see where the balls are coming from in time, or there'll be 20-30 balls at once which you'll all have to hit to get 1 point extra.