Strictly not a bug, but having just been given an iPhone 4 running iOS 7 I wanted to download the MemRise app, only to be told I need iOS 9 (ie a modern phone).
Shame as I wanted to join the experience on an app as well as testing the many courses I’ve created and am supporting here on the web.
As far as I know you can’t get older versions of the iOS app. However, we’re currently working on making the website fully responsive, so the mobile experience on the web should be a lot better in the coming months!
I hope the computer (MAC or PC) web browser versions will remain like they are now as many of us long-standing faithful and committed contributors prefer that version.
Responsive design basically means that a website adapts to the screen size etc of the device used, it does not mean that it will look or work like the app for that platform. An app is a very different animal from a responsive website.
With today’s HTML 5 Javascript support with most mobile browsers you could get pretty close to natiive-style UI design – as a side benefit it also scales across all platforms, mobile or non-mobile.