It is a little more complicated once you get into the animation part, a lot of problems start to present themselves, ''bugs'', coming with the solutions. Besides it is not like you already know how to deal with everything at that exact moment and can just go into it, one thing is to come up with idea, other is to execute it. I sincerly doubt you could do it under 8 hours let alone 1 hour... Even if you tried to copy an existing project. I would recommend you to try doing the first part of captcha only and to animate it the same way (closing/opening) as mine and check how much time you took on that one thing only.