At the moment we offer full support for Chrome and Firefox under Win, Mac and Linux.
The latest version of Safari works under the latest version of macOS (Sierra); older versions of either may be hit and miss. If it doesn't work for you please try either Firefox or Chrome.
On iPad the browser version works; on Android tablets it's functional as well, though there can be problems with reordering of cards, as well as some display oddities depending on screen size.
Phones are not supported at the moment.