Instruction: Analyze the user's review text and determine the overall sentiment expressed, then choose the corresponding sentiment option from the provided list (A: very positive, B: positive, C: neutral, D: negative, E: very negative) based on the identified sentiment.

Input:
This is an optical trackball with a one inch diameter red ball (the marble in "marble mouse") that moves within a three point holder with an optical pickup.
Only the ball moves.
There are four buttons. It is perfectly designed, very simple and effective.
It is quite different than a moving mouse, and faster too.
It takes a few minutes to get used to, but once you do, you may never want go back to a moving mouse again, mouse pad and all

This is just the thing to end repetitive motion pain and injury, especially if you turn up the mouse sensitivity or "acceleration".
It is easy to clean, just pop out the red ball and wipe the holder.

And believe it or not, I have seen expert gamers using it very effectively, and I swear they were faster than their competition.

I use it for all my mundane computer work and no longer suffer from "mouse hand" pain.
The price is right too, at between 14 and 20 dollars.

Options:
A: very positive
B: positive
C: neutral
D: negative
E: very negative
Answer: A: very positive