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Etterna has quite a large amount of specific terms that are not quite immediately obvious to what they mean. This page will provide the definition to all of the most common terms used along with pictures when needed.
The most immediate things which you should be aware of, as you will be encountering them when you first open the game. It is highly recommended to understand these terms.
MSD - An acronym for Mina Standardized Difficulty, which refers to the generated numerical value a file is given by the game. This calculator is to be taken as a general guideline for what to expect and it not meant to serve as an absolute metric. This value is based on what the game will give a player upon completing the file with a score of 93% WIFE Scoring, and will scale upward to varying degrees from file to file as your performance improves up to 96.5% WIFE Scoring. Below is an image showcasing the seven categories of difficulty assessment:
WIFE - The percentage system that dictates your overall grade on a file. As you play, every millisecond counts towards your performance, as opposed to having arbitrary hard judgment lines. The closer you are to hitting the arrows exactly, the higher your percentage for it will be, while outright missing the arrows will net you a tough additional penalty. For quick reference, the following grades are obtained when you hit certain percentages:
Stream - A series of single arrows, or taps, not repeating on the same arrow column. Streams in the MSD actually account for several types of patterns, which will be discussed more thoroughly in the proceeding sections. Here is a general example of a chart that would be rated in the stream category.
Jumpstream - A series of double arrows, or jumps, with taps in between them. The amount of taps between the jumps will make the jumpstream either more or less dense, altering it's difficulty. An example of jumpstream for better understanding.
Handstream - A series of triple arrows, or hands, with taps in between them. Follows the same rules as jumpstream, and an example can be seen here.
Stamina - Refers to your ability to maintain patterns for a long period of time. Charts with high stamina ratings will generally have large portions of the file maintaining a constantly fast set of patterning (which can be any or all of the other categories). I cannot realistically provide an example of stamina in image format, but consider playing any of the other shown patterning for long periods of time without breaks, and at speeds which could tire you out.
Jackspeed - A set of arrows which repeat on the same column(s). This can be anything from a tap, all the way up to just repeatedly hitting all four notes (quads) at once. Here is an example of jackspeed on a single arrow.
Chordjack - A group of different triple arrows, or hands repeating. The chordjacks can be made less dense by interspersing jumps or taps in between the hands, so long as the result is still a largely jacking set of patterning instead of streaming. Here is an example of chordjacks with less density, for a better understanding.
Technical - A set of patterning that the calculator considers unfriendly and awkward to hit, and can stem from any of the other categories. Sudden bursts of arrows, jacks, gluts (varying jump patterns), or polys (16th/32nd mixed with 12th/24th/48th at the same time) are a good thing to be on the look out for. Example of an intense technical pattern.