A PC that can run the core game, and a smartphone for each player, all connected on the same WiFi network. Internet connectivity is not required.
iPhone:
Requires iOS8 or later. Compatible with iPhone 4s or later, iPad Mini, iPad 2 or later. This app is optimized for iPhone 5s.
Android:
Requires an Android phone or tablet with at least 512mb or RAM and Android 4.1 ‘Jellybean’ or later.