Most of the Steam Achievements are unlocked correctly when you obtain then offline (without internet connection but still playing through Steam) but some of them just dont... for example, you are able to unlock all the skill trees achievements while offline, the next time you log in with a working Internet connection you should get them. But all the Steam Achievements that needs to count something or check if you are wearing a piece of armor, do not trigger while playing offline. For example, with the achievement that ask you to to kill Digglets you can kill all the Digglets you want but they do not count if you are not online. Also the one where you need to break Dredmor´s statues, craft potions... the count only goes up when you play while connected to Internet. The same is true for the achievements that ask you to wear a specific piece of armor like the combo of Rust Helm and Green Armor. My suggestion is to improve the way the game checks if you unlocked at achievement or not, and add some sort of fix for the game to track your progress in the achievements that ask you to do something a specific number of times.
