I'm playing Skyforce both on my phone and on my tablet (mostly on my phone because it has a pen) but my progress isn't being synchronized. The game always is in an older state on the tablet. Is this a known problem of Skyforce or Google Play or is there a way to synchronize them?
This is not an issue with the Google Play Games cloud save feature, but Infinite Dream's implementation of cloud save (if it's even an issue, since this is probably working as Infinite Dreams intended). Regardless of the technology that Infinite Dreams is using to store cloud saves, it's up to the developer to decide what data is stored in the cloud save, and it looks like they chose to sync ship upgrades, but not stars (http://forums.toucharcade.com/showthread.php?t=288639&page=12).