There are two files you can download: the installer package, or the simple double-click-and-play-because-you're-lazy program.
There is now also an Android app!
To download the installer, click here.
To download the other one, click here.
To download the Android app, click here. Copy it to anywhere on your phone and install it from there. (Make sure you have "Unknown Sources" ticked in your phone's security settings)