This is an informative document on how the charts in Chunithm are formatted and function. This is not meant to be a complete guide on how to create custom charts for Chunithm. All information on this document was discovered via personal research. Contributions and further research are welcome. This document may be used for any purpose, including the creation of a tool to create Chunithm charts. See UNLICENSE for more information.

Things to know

• Most counting in this file format starts from 0. A measure of 0 means at the beginning of the song, a cell of 0 means the first cell on the left, etc.
• The location for song files on most versions of the game can be found in Chunithm¥app¥data¥¥AXXX¥music¥musicXXXX. The file format for charts is .c2s, and are plain text files that can be opened in tools like Notepad++.
• A cell is the corresponding key for the note on the playfield. The playfield has 16 columns, numbers from 0-15 from left to right.
• A measure is a function of time containing a specific amount of beats. Each measure usually contains 4 beats, and stays relatively consistent throughout the song.

Tags

BPM

Designates the BPM for the specified measure of the song.

Schema:

Beginning Measure	Offset	BPM

MET

?

Notes

Universal Note Schema

Note Type	Measure	Offset	Cell	Width

Note Type

A note type is the type of note that you want to be placed at this particular point. There are various types of notes that can be used, and most of them will have additional variables that will be appended to the end of the typical schema. There will be more information later on explaining each of these notes.

Note Types:

• TAP (tap)
• CHR (ex-note)
• HLD (hold)
• SLD (slide)
• SLC (slide control point)
• FLK (flick)
• AIR (air)
• AUR (air up-right)
• AUL (air up-left)
• AHD (air hold)
• ADW (air downwards)
• ADR (air down-right)
• ADL (air down-left)
• MNE (mine)

Measure

The measure is the specific measure that you want the note to be placed in. Each measure is (usually) 4 beats. The value starts from 0 and continues infinitely, although should always end with the song.

Offset

A function of time to show how offset a note or timing point should be from the measure. This relies on the resolution of the song, designated by the RESOLUTION tag. The full resolution is an entire measure, so with a resolution of 384, the first beat of a measure would be 0, the second would be 96, the third would be 192, the fourth would be 288. To get the desired beat, divide the resolution by 4, multiply it by the beat that you want, and then subtract it by the resolution divided by 4.

For a fraction of a beat, divide the resolution by 4, then multiply it by the fraction of the beat you want. Then add that result with the desired beat.

The function for this would be:

b(r/4)-(r/4) + f(r/4)

where b is the desired beat rounded down to a whole number, r is the resolution of the song, and f is the fraction of the beat.

For example, if I wanted a note on the 2 1/2th beat of a 4 beat song with a resolution of 384, I would perform the following:

2(384/4)-(384/4) + 1/2(384/4)
192 - 96 + 48
144

Cell

As stated above, the cell is the numerical ID for the column in the playfield that the note should appear in. Note that this value should be the column that the note first appears in from the left.

Width

Separate from the Cell value, the Width value notes how wide the note should be, extending from the value listed in Cell to the right. The minimum value is 1, which means that the note only occupies the column listed in cell. As an example, a width of 3 on a note with a cell value of 7 would have the note occupy columns 7, 8, and 9.

Additional Note Values

Most note types require additional information to function correctly. This section will provide an example of the schema that the note uses, followed by an explanation for any values not included in the universal schema. Any values in quotes indicate a value that is consistent with that note.

Tap

Tap notes are the most basic notes that can be charted. They simply require the player to hit the cell that the note occupies at the required time.

Schema:

"TAP"	Measure	Offset	Cell	Width

Tap notes do not differ from the universal schema listed above.

Ex-Notes

Ex-Notes are similar to tap notes, although they give the player more score for hitting them accurately.

Schema:

"CHR"	Measure	Offset	Cell	Width	Unknown

• Unknown: Seems to always have a value of "UP" or "CE".

Hold

Hold notes are similar to tap notes, but require the player to keep the designated cell pressed over a continuous period of time.

Schema:

"CHR"	Measure	Offset	Cell	Width	Duration

• Duration: The amount of time that the note needs to be held down for. This value is based on the same format for offset.

Slide

Slide notes are similar to hold notes, but are capable of moving between cells while sustaining the hold. There are two types of slide notes, SLD and SLC. Slides that start with a straight line begin with an SLD, while slides that start immediately with movement start with an SLC. All slides end with an SLD note.

Schema:

"SLD"/"SLC"	Measure	Offset	Cell	Width	Duration	End Cell	End Width

• Duration: The amount of time that the note will take to move to the target cell. This value is based on the same format for offset.
• End Cell: The column that the slide will move towards over the duration of the slide. Similar to the Cell value, this value will be where the left side of the cell is, and can be anywhere from 0-15. To have a slide that stays straight over the duration, make the End Cell value the same as the Cell value.
• End Width: The width that the slide will have at the end of the duration. Similar to the Width value, this value can be anywhere between 1-16. If the End Width differs from the original Width, the slider will gradually shrink or expand in width over the course of the slide.

A slide will not end until you call an SLD in the same cell that another slide is in at that moment in time. To adjust a slide without interrupting it, use SLC.

The feature of sliders shaking from side to side rapidly is not a built-in function of the game, it instead simply involves having the slider move left and right a few cells on very short offsets.

Flick

A flick note involves the player having their finger within the cells that the flick inhabits, and then swiping to the left or the right depending on which direction the flick has.

Schema:

"FLK"	Measure	Offset	Cell	Width	Direction

• Direction: The direction that the user is meant to swipe in. The possible values are "L" for left and "R" for right.

Air

An air note involves the player raising their hands through the IR sensors above the physical keyboard. Unlike other notes, these notes act as modifiers for already existing notes. There are also different cosmetic versions of the note, however they each function identically.

Schema:

"AIR"/"AUR"/"AUL"	Measure	Offset	Cell	Width	Target Note

• AIR/AUR/AUL: Each of these note types are identical functionality-wise, although affect the appearance of the arrow above the note. AIR has an upwards arrow, AUR has an up-right arrow, and AUL has an up-left arrow.
• Target Note: This value designated what note the Air note "leeches" off of. You should have this note be in the same cell, measure, and offset as the Air note. It's also recommended to only use this note at the end of a note, rather than in the middle of a sustained note. This recommendation can be discarded for high-level charts.

Air Hold

An air hold note involves having the player hold their hands up towards the sensor after performing an air note. Air holds will always end with a mid-air downwards note automatically.

Schema:

"AHD"	Measure	Offset	Cell	Width	Target Note	Duration

• Target Note: This value designated what note the Air note "leeches" off of. You should have this note be in the same cell, measure, and offset as the Air note. It's also recommended to only use this note at the end of a note, rather than in the middle of a sustained note. This recommendation can be discarded for high-level charts.
• Duration: The amount of time that the note will take to move to the target cell. This value is based on the same format for offset.

To have mid-air downwards notes in a sustained air note, make the first air hold note last until the point where the mid-air note would be, then add another air hold note that starts at the same offset where the preceeding air hold note ends.

Downwards

A downwards note involves the player lowering their hands through the IR sensors above the physical keyboard. Unlike other notes, these notes act as modifiers for already existing notes. There are also different cosmetic versions of the note, however they each function identically.

Schema:

"ADW"/"ADR"/"ADL"	Measure	Offset	Cell	Width	Target Note

• ADW/ADR/ADL: Each of these note types are identical functionality-wise, although affect the appearance of the arrow above the note. ADW has a downwards arrow, ADR has a down-right arrow, and ADL has a down-left arrow.
• Target Note: This value designated what note the downwards note "leeches" off of. You should have this note be in the same cell, measure, and offset as the downwards note. It's also recommended to only use this note at the end of a note, rather than in the middle of a sustained note. This recommendation can be discarded for high-level charts.

Mines

A mine note involves the player not touching the cell that the mine is placed on. Touching the cell will result in the player losing score and possibly failing the track.

"MNE"	Measure	Offset	Cell	Width

Mine notes require the same information as Tap notes, and simply follow the universal schema mentioned above.

Demonstration

Below is an excerpt from the .c2s file for Cyaegha's MASTER difficulty, which has a RESOLUTION of 386.

TAP	8	0	6	4
TAP	8	0	12	4
SLC	8	96	4	4	7	3	4
TAP	8	96	10	4
SLC	8	103	3	4	10	2	4
SLC	8	113	2	4	13	1	4
SLC	8	126	1	4	22	0	4
SLD	8	148	0	4	236	0	4
TAP	8	192	8	4
SLC	8	288	6	4	4	7	4
SLC	8	292	7	4	12	9	4
SLC	8	304	9	4	9	10	4
SLC	8	313	10	4	12	11	4
SLC	8	325	11	4	23	12	4
SLD	8	348	12	4	36	12	4
AHD	9	0	0	4	SLD	192
CHR	9	0	4	8	CE
AIR	9	0	4	8	CHR
AHD	9	0	12	4	SLD	192
TAP	9	288	3	4
TAP	9	288	9	4

Below is what the gameplay for this section looks like. This will be broken down into each line of the .c2s file to see their corresponding patterns in gameplay.

The two tap notes at the beginning appear as:

TAP	8	0	6	4
TAP	8	0	12	4

The order of values in these lines is the following:

Tap note | on the 8th measure | with an offset of 0 | starts on cell 6/cell 12 | extends 4 cells to the right

You can tell that these notes are supposed to occur at the same time because the share the same measure and offset. Remember that the cells are labelled as 0-15, meaning that the first cell on the left is cell 0.

The next two notes are a slide and a tap that occur at the same time. These appear in the document as:

SLC	8	96	4	4	7	3	4
TAP	8	96	10	4

Note that the slide has the note type of SLC, since the slider starts in motion. If the slider was stationary at the beginning, it would've had an SLD note type.

The order of values for the slide note is the following:

Slide note | on the 8th measure | with an offset of 96 | starts on cell 4 | extends 4 cells to the right | has a duration of 7 resolution | ends on cell 3 | ends with a width of 4

There are a few important things to note here. For one, with a measure of 8 and an offset of 96, this means that the note happens on the second beat of the 8th measure (remember, an offset of 0 means the first beat). It also has a very short duration, at only 7 resolution. This means that the slider only lasts for almost 2/100th of a measure. The reason it's so short is because it's designed to look like a curve. There are later SLC notes that attach to the first slider that gradually change to the shape to a curve.

The tap note later on has an order of values of:

Tap note | on the 8th measure | with an offset of 96 | starts on cell 10 | extends 4 cells to the right

Again, since the two notes occur at the same measure and offset, they are simultaneous.

The next notes are several control points for a slider, as well as creating a new slider, and a tap note. Their lines are:

SLC	8	103	3	4	10	2	4
SLC	8	113	2	4	13	1	4
SLC	8	126	1	4	22	0	4
SLD	8	148	0	4	236	0	4
TAP	8	192	8	4
SLC	8	288	6	4	4	7	4
SLC	8	292	7	4	12	9	4
SLC	8	304	9	4	9	10	4
SLC	8	313	10	4	12	11	4
SLC	8	325	11	4	23	12	4
SLD	8	348	12	4	36	12	4

There are several important things to note here. For one, the SLCs at the top are within very quick succession of each other. As stated above, this is because it's creating a curved slider, so it's very precise to look smooth. There is also an SLD immediately after it, which has a duration of 236 resolution. This is important because you can see that this slider is supposed to end at the same time as the other slider. If you add together the offset, which is 148, and the duration, you'll get a value of 384. If you add together the offset and duration of the second SLD at the bottom, you also get 384. Since they are both on the same measure, this shows that they will end at the same time as each other. It's also worth mentioning that the second pair of SLCs are not related to the first pair. They start on a separate cell from the other slider, so it creates a new slider instead of extending a previous one.

The final part of the excerpt contains several air notes, an air hold, an ex-note, and several tap notes. These appear in the file as:

AHD	9	0	0	4	SLD	192
CHR	9	0	4	8	CE
AIR	9	0	4	8	CHR
AHD	9	0	12	4	SLD	192
TAP	9	288	3	4
TAP	9	288	9	4

You'll notice that both AHDs, the AIR, and the CHR notes all start at the same time, since they share the same measure and offset. Let's break down each note.

The AHD notes represents the following:

Air hold note | on the 9th measure | with an offset of 0 | starts on the 0th cell/12th cell | extends to the right by 4 cells | leaches off of the Slider note that occupies that same cell | has a duration of 192 resolution

The CHR note represents:

Ex-note | on the 9th measure | with an offset of 0 | starts on the 4th cell | extends to the right by 8 cells | CE modifier

The AIR note represents:

Air note | on the 9th measure | with an offset of 0 | starts on the 4th cell | extends to the right by 8 cells | leaches off of the ex-note that occupies the same cell

The excerpt finally ends with two TAP notes, which mean the following:

Tap note | on the 9th measure | with an offset of 288 | starts on the 3rd/9th cell | extends to the right by 4 cells

This concludes the analysis of this excerpt of Cyaegha.

Disclaimer

This document does not condone the illegal piracy, operation, modification, or reverse engineering of Chunithm arcade games, nor any games licensed by Sega, as such actions may violate Japanese and international law.