Wanted: Simple Capthcha for Forms, Maybe a Random Question or Image

Hi, I am looking for a simple caphcha for my forms on my zen cart site. Maybe one that uses a random math question like "what is 1+5" or maybe one what shows a random image of a common animal like a dog, cat, pig, tiger, or horse and the person has to answer what animal they see. Does anyone know of one for zen cart? Thank you!

The reason I am asking is because the common caphcha is a pain for most people and frustrates them (me included). There must an easier way to block the spammers/bots without upsetting potential customers.

If you are using Zen Cart v1.5.1 or newer, there's a built-in anti-spam trap already present which makes captcha unnecessary.