Bought as I can resist these types of games.
There's three control options,
The first is auto, where to press to expand the circle and release to decrease it.
The second is manual where you press right to increase and left to decrease, the direction changes with each item collection.
The last option is full, where you tap right to increase the circle, release to decrease and tap left to change direction.
I've tried all and prefer the middle option as the circle stays where you want to until you need to change. Disadvantage if this is no control over the direction, how about implementing something like pressing both sides to control direction?
Each set has it's advantages but there needs to be an option to control all aspects, I do much better with manual selected but it could be a lot better if I could also control the direction, the last option means you lose control if the radians as it's always moving with a press and can't stay static.
It also needs a pause button.
With a few tweaks to the controls this could be awesome, don't get me wrong it's still good as it is, it just lacks something.