Rank is not important for the purposes of leaderboards, since leaderboards are ordered by score only (except for Infinity Drive and Daily Drive which are ordered by completion layer, then score). The highest-scoring runs are often incidentally going to be S+ anyway, since you always want to keep up Combo for score purposes.
|D||No special requirement, just complete the level.
A D rank indicates a poor score, usually with frequent knockdowns.
|C||Like D, but with a somewhat better score.
Indicates a mediocre score, usually with multiple knockdowns.
|B||Like C, but with a somewhat better score.
Indicates an average score.
|A||Like B, but with a somewhat better score.
Indicates a good score.
If you get knocked down at least once, this is the highest rank you can receive, regardless of how good your score is.
|S||Complete the level without any knockdowns, and also get a very good score.|
|S+||The same as S rank, with the added restriction that you must not drop Combo at any point.
In Multiplayer, all players must hold Combo in order to earn an S+.
Technically, the requirement for S+ is no knockdowns, and each player's killcount is equal to their maximum combo length.
|Purple S+||Not actually a rank per se, but signifies that you've achieved an S+ rank in a level with every Android.
Manifests as a purple, rotating "S+" aura around a level's teleporter in the level selection screen (see Campaign Levels for what this looks like).
Getting an S+ rank in any level unlocks Pro Mode. In the options, you can enable an S+ indicator which appears to the left of the battery. If Combo drops at any time, it will smash with a loud noise and sparkly visual effect, indicating that this run is no longer eligible for an S+ rank.
You can also opt to automatically restart when the indicator is smashed, which is accompanied by a unique black-and-white screen filter.
If auto-restart is on, the S+ indicator appears purple. If not, it appears blue.
Pro Mode also grants access to the quick-restart shortcut (Select on most controllers, R on the keyboard)
Corner case: Dropping combo, but still receiving an S+ rank
If at the end of a level, you drop Combo but the remaining enemies die to each other (or environmental damage), you still receive an S+ rank.
This is because the real criterion for S+ is that your kills is equal to your maximum combo (and you have no knockdowns)
|Assault Android Awesome||Earn an S+ ranking on all Campaign Levels||The hardest achievement, there's no easy way around it. You just have to learn to hold onto the chain and not die.
While any android will work, Starch or Holly are the easiest for most regular levels, while Cactus is a good choice for bosses. Shiitake is probably the most challenging for regular levels, and Aubergine is probably the most challenging for bosses.
Completing this achievement will award you an in-game congratulatory splash screen, and a special alternate skin for Peanut.
|Perfection||Earn an S+ Rank on any level||To earn an S+ you need to complete an entire level without dropping Combo at any time.|