Great plugin - thank you. I use it with Contact Form 7 and it provides a nice simple captcha. But I'm hitting a snag with people viewing the site on retina devices (e.g. iphone). I'm getting lots of 404 errors which are related to WPCF7_CAPTCHA files where the missing file name is suffixed with @2x.png. That's the suffix for retina images. So I assume that Really Simple Captcha is not generating the retina version of the captcha image. I don't own a retina device but I have read that what happens when this occurs is that the client sees the "ALT" text on their device instead of an image. That would, of course, make it impossible for them to see the captcha image and impossible for them to send their details in the form. I'm going to find a friend with an iphone and check it out. In the meantime I thought I should check if you have any plans to generate the @2x.png version of the captcha file someday in the future. As far as I know it is just a double size file (2 x pixels in both direction) which I imagine is not that difficult to render for you since you already have different sizing classes. Thanks again for the great plugin.