....because one day, this kind of CAPTCHAS is going to be every where.
Examples of animated captcha:

Write everything you see in order

Examples of math captcha:

\sum _{n=0}^{\infty} \frac{(\int _{-\infty}^{\infty}\exp(-a^2)da)^2 \oint \frac{dz}{z}}{4{\prod_{k=1}^\infty(\frac{n+1}{n})^{(-1)}^{n-1}} n!} = i\sum _{n=0}^{\infty} \frac{(-1)^n x^{2n+1}}{(2n+1)!} + \sum _{n=0}^{\infty} \frac{(-1)^n x^{2n}}{(2n)!}

Examples of logic captcha:
The smallest positive integer not definable in under eleven words:

I had a dream yesterday. I'm so rich, I go to at&t and buy a iPhone. But sadly, I can't get it because it released on June 29.

When a bear ask you if you want a hug, say no.

I'm so pissed that I didn't get "Outstanding Sophomore Mathematician"
"WTF, Where is CHao XU? This is F*(! Mathematics runs in my veins! My blood cells look like numbers! My liver looks like Sigma!!
"I'm eating Chao right now... Puff.. what's that...ewww.. his muscle is made up of Pi"
I don't predict the future, I prove the future!
That's how good I am with math!
But, who need that reward anyway.
if I present reward like this to any college at some interview..
Interviewer:"WTF, don't F*(!< with me! What is this? this is $h!+!. Leave now, now! Don't ever come back, you stupid Asian!"

I mean my math runs in my blood.
Someone punches in the face and then stare at me in horror.
Because there is no BLOOD, it's all numbers.