Topological and Other Strange Captchas

Most Captchas aim to separate humans from spambots, but a few creative Captchas floating on the Web probably aim to separate the super-humans from the mere mortals. Tongue-in-cheek aside, I'd definitely like to see more topological Captchas like the one above.

Geek Technica has a neat list of 10 such Captcas that have gone a bit too far in proving that you're human:

Newest 5
Newest 5 Comments

Damn, if it isn't C because every single intersection on the fold out has three lines, yet the top left side of C shows a white line crossed only by one other dark green line.

Took me more than 29 seconds though.

ln(2) for the math limit one, because arctan(x) goes to 0 while sin(1/x) can only bounce back and forth widely between -1 and 1. However, the sqrt won't like the parts of the function when sin(1/x) is negative, but if sqrt(-1) is allowed and we make this a complex function you would still get to ln(2) eventually. Probably should expand the functions into Taylor series and then do the limit (maybe use L'Hopital's rule also) to get a more rigorous result. Coincidentally, It also goes to ln(2) when x goes to infinity, this time because sin(1/x) goes to zero.

Abusive comment hidden. (Show it anyway.)
Is it C? There doesn't seem to be a match on the layout to the side of C that is facing us. (there's no cross of a terminating light green and black over a terminating yellow.

I think it might be E. But I'm not sure.
Abusive comment hidden. (Show it anyway.)
All kidding aside, these would be bad for me. As I cannot visualize the answer (though one of my sons, at age 5 could easily have done this), I would never succeed.
Abusive comment hidden. (Show it anyway.)
Login to comment.

Email This Post to a Friend
"Topological and Other Strange Captchas"

Separate multiple emails with a comma. Limit 5.


Success! Your email has been sent!

close window

This website uses cookies.

This website uses cookies to improve user experience. By using this website you consent to all cookies in accordance with our Privacy Policy.

I agree
Learn More