v0.9.0 means we're really close to leaving Early Access and ready to start implementing Steam-specific features. This update includes, with a few caveats:
Cloud Saves
Game settings, achievement progress, and local high scores are all part of cloud saving.
Achievements
The achievements are currently in-game only in case we need to change some of them based on feedback. Your achievement progress is saved, though, so when achievements are officially added to Steam, it won't take much to unlock them.
Also note that, in the final version of the game, Hard Mode and Big Mode will be locked until a certain number of achievements are earned. For now, both options are still available to play without any prerequisites.
Here's the full list:
Leaderboards
Leaderboards can be accessed through the Community Hub and are broken up into eight sub-boards to represent each combination of the game: playing solo on normal mode with a normal playing field, playing co-op on hard mode with a big playing field, etc.
Keep in mind that leaderboards might need to be reset once the game leaves Early Access if any tweaks are made to the difficulty balance between now and then.