Charting System - Friday Night Funkin'

The charting system defines note placement, events, and gameplay data for songs in Friday Night Funkin’.

Chart Data Format

Chart data is stored in assets/data/songs/[id]/[id]-chart.json:

{
  "version": "2.2.4",
  "scrollSpeed": {
    "easy": 1.0,
    "normal": 1.5,
    "hard": 2.0
  },
  "events": [
    {
      "t": 0,
      "e": "FocusCamera",
      "v": {"char": 1}
    },
    {
      "t": 4000,
      "e": "FocusCamera",
      "v": {"char": 0}
    }
  ],
  "notes": {
    "easy": [
      {"t": 1000, "d": 0, "l": 0},
      {"t": 1500, "d": 1, "l": 0},
      {"t": 2000, "d": 2, "l": 0},
      {"t": 2500, "d": 3, "l": 0}
    ],
    "normal": [
      {"t": 1000, "d": 0, "l": 250},
      {"t": 1500, "d": 1, "l": 0},
      {"t": 2000, "d": 2, "l": 500},
      {"t": 2500, "d": 3, "l": 0}
    ],
    "hard": []
  },
  "generatedBy": "FunkinCrew Chart Editor"
}

Chart Data Fields

version

String

required

Chart format version (currently “2.2.4”)

scrollSpeed

Map<String, Float>

required

Scroll speed for each difficulty (controls note speed)

events

Array<SongEventData>

required

Array of song events (camera focus, animations, etc.)

notes

Map<String, Array<SongNoteData>>

required

Note data for each difficulty

generatedBy

String

Tool or person that generated this chart

Song Note Data

Each note is defined with minimal data:

class SongNoteData
{
  public var t:Float;    // Time (in song's time format)
  public var d:Int;      // Direction (0-7)
  public var l:Float;    // Length (0 = regular note, >0 = hold note)
  public var k:String;   // Kind (optional, for special note types)
}

Note Fields

Float

required

Time when the note should be hit (format depends on song’s timeFormat)

Int

required

Note direction/lane (0-3 for opponent, 4-7 for player)

0/4 = Left
1/5 = Down
2/6 = Up
3/7 = Right

Float

default:"0"

Hold note length in milliseconds (0 = regular note, >0 = sustain)

String

Note kind ID for special note types (e.g., “mine”, “hurt”)

Note Direction Mapping

Opponent strumline (left side):

0 = Left
1 = Down
2 = Up
3 = Right

Player strumline (right side):

4 = Left
5 = Down
6 = Up
7 = Right

enum abstract NoteDirection(Int)
{
  var LEFT = 0;
  var DOWN = 1;
  var UP = 2;
  var RIGHT = 3;
}

// Convert to player lane
var playerLane = baseDirection + 4;

Note Types

Regular Notes

Standard notes that must be hit:

{"t": 1000, "d": 0, "l": 0}

Hold Notes (Sustains)

Notes that must be held down:

{"t": 1000, "d": 0, "l": 500}

Hold for 500ms after the note starts. The l field defines the hold duration. Hold note scoring:

Player must hit the note head
Player must hold the key for the sustain duration
Releasing early breaks the hold
Each sustain “segment” can award points

Special Note Kinds

Note kinds modify behavior:

{"t": 1000, "d": 0, "l": 0, "k": "mine"}

Built-in note kinds:

Default (no k field): Standard note
Custom kinds defined in assets/data/notekind/ directory

Custom note kinds can:

Change note appearance
Modify hit behavior
Award different points
Trigger special effects

Song Events

Events trigger gameplay actions at specific times:

class SongEventData
{
  public var t:Float;         // Time
  public var e:String;        // Event kind
  public var v:Dynamic;       // Event value (data)
  public var activated:Bool;  // Internal tracking
}

Event Structure

{
  "t": 4000,
  "e": "FocusCamera",
  "v": {
    "char": 1,
    "duration": 1.0
  }
}

Float

required

Time when event triggers (in song’s time format)

String

required

Event kind/type identifier

Dynamic

Event-specific data (can be any JSON-serializable value)

Built-in Events

FocusCamera

Changes camera focus to a character:

{
  "t": 1000,
  "e": "FocusCamera",
  "v": {
    "char": 1
  }
}

Parameters:

char: Character index (0 = player, 1 = opponent, 2 = girlfriend)
duration: Optional tween duration in seconds

ZoomCamera

Changes camera zoom level:

{
  "t": 2000,
  "e": "ZoomCamera",
  "v": {
    "zoom": 1.2,
    "duration": 0.5
  }
}

Parameters:

zoom: Target zoom level
duration: Tween duration in seconds

PlayAnimation

Plays animation on a character or prop:

{
  "t": 3000,
  "e": "PlayAnimation",
  "v": {
    "target": "dad",
    "anim": "hey",
    "force": true
  }
}

Parameters:

target: Character or prop name
anim: Animation name
force: Whether to interrupt current animation

SetCameraBop

Controls camera bopping:

{
  "t": 4000,
  "e": "SetCameraBop",
  "v": {
    "intensity": 0.015,
    "rate": 4
  }
}

Parameters:

intensity: Bop strength (zoom amount)
rate: Bop every X beats (e.g., 4 = every 4 beats)

Scroll Speed

Controls how fast notes move:

{
  "scrollSpeed": {
    "easy": 1.0,
    "normal": 1.5,
    "hard": 2.0,
    "expert": 2.5
  }
}

Scroll speed values:

1.0 = Default speed
<1.0 = Slower (more reaction time)
>1.0 = Faster (less reaction time)
Typical range: 0.8 - 3.0

How scroll speed affects gameplay:

Higher values = notes approach faster
Lower values = more time to react
Does NOT affect timing windows
Purely visual speed change

Chart Organization

Per-Difficulty Charts

Each difficulty has separate note data:

{
  "notes": {
    "easy": [
      {"t": 1000, "d": 0, "l": 0},
      {"t": 2000, "d": 1, "l": 0}
    ],
    "normal": [
      {"t": 1000, "d": 0, "l": 0},
      {"t": 1500, "d": 2, "l": 0},
      {"t": 2000, "d": 1, "l": 0}
    ],
    "hard": [
      {"t": 1000, "d": 0, "l": 250},
      {"t": 1250, "d": 2, "l": 0},
      {"t": 1500, "d": 1, "l": 0},
      {"t": 1750, "d": 3, "l": 0},
      {"t": 2000, "d": 0, "l": 500}
    ]
  }
}

Difficulty design guidelines:

Easy: Fewer notes, simpler patterns, longer gaps
Normal: Moderate note density, basic patterns
Hard: Higher density, complex patterns, more sustains

Shared Events

Events are shared across all difficulties:

{
  "events": [
    {"t": 0, "e": "FocusCamera", "v": {"char": 1}},
    {"t": 4000, "e": "FocusCamera", "v": {"char": 0}}
  ]
}

Camera changes, animations, and other events apply to all difficulties.

Note Patterns

Single Notes

Basic rhythm:

[
  {"t": 1000, "d": 0, "l": 0},
  {"t": 1500, "d": 1, "l": 0},
  {"t": 2000, "d": 2, "l": 0},
  {"t": 2500, "d": 3, "l": 0}
]

Chords

Multiple simultaneous notes:

[
  {"t": 1000, "d": 0, "l": 0},
  {"t": 1000, "d": 2, "l": 0}
]

Both notes at the same time (t: 1000).

Rolls

Rapid sequential notes:

[
  {"t": 1000, "d": 0, "l": 0},
  {"t": 1125, "d": 1, "l": 0},
  {"t": 1250, "d": 2, "l": 0},
  {"t": 1375, "d": 3, "l": 0}
]

Holds (Sustains)

Long notes:

[
  {"t": 1000, "d": 0, "l": 1000},
  {"t": 2500, "d": 1, "l": 500}
]

First note holds for 1 second, second for 0.5 seconds.

Jacks

Repeated notes in same lane:

[
  {"t": 1000, "d": 0, "l": 0},
  {"t": 1250, "d": 0, "l": 0},
  {"t": 1500, "d": 0, "l": 0},
  {"t": 1750, "d": 0, "l": 0}
]

Timing Precision

Chart timing uses the song’s time format:

Milliseconds (Most Common)

{"t": 1234.5, "d": 0, "l": 0}

Direct millisecond timing. Precise to 0.1ms.

Ticks

{"t": 384, "d": 0, "l": 0}

With divisions: 96:

1 beat = 96 ticks
1/4 beat = 24 ticks
1/16 beat = 6 ticks

Grid-aligned, no floating point errors.

Step Alignment

Notes should align to musical steps: 4/4 time, 120 BPM:

1 beat = 500ms
1 step (1/4 beat) = 125ms

Common note timings:

Quarter notes: 500ms apart
Eighth notes: 250ms apart
Sixteenth notes: 125ms apart
Thirty-second notes: 62.5ms apart

Loading Charts

Charts are loaded via the Song system:

var song = SongRegistry.instance.fetchEntry("bopeebo");
var difficulty = song.getDifficulty("hard");

// Access chart data
var notes = difficulty.notes;  // Array<SongNoteData>
var events = difficulty.events; // Array<SongEventData>
var scrollSpeed = difficulty.getScrollSpeed();

Charting Best Practices

1. Follow the Music

Align notes to musical beats:

Use strong beats for emphasis
Match note patterns to melody
Use holds for sustained notes

2. Difficulty Progression

Easy:

Simple patterns
Mostly single notes
Clear beat alignment
Minimal holds

Normal:

Moderate complexity
Some chords (2 notes)
Basic patterns
Occasional holds

Hard:

Complex patterns
Frequent chords
Fast rolls
Long holds
Creative patterns

3. Playtest Extensively

Test on different difficulties
Check timing accuracy
Verify event triggers
Ensure patterns are fair

4. Use Events Effectively

Camera focus on singing character
Zoom for emphasis
Animations at key moments
Don’t overuse effects

5. Balance Opponent and Player

Opponent notes (d: 0-3) during their sections
Player notes (d: 4-7) during player sections
Can overlap during duets

Example: Complete Chart

{
  "version": "2.2.4",
  "scrollSpeed": {
    "easy": 1.0,
    "normal": 1.5,
    "hard": 2.0
  },
  "events": [
    {
      "t": 0,
      "e": "FocusCamera",
      "v": {"char": 1}
    },
    {
      "t": 8000,
      "e": "FocusCamera",
      "v": {"char": 0}
    },
    {
      "t": 12000,
      "e": "ZoomCamera",
      "v": {"zoom": 1.3, "duration": 0.5}
    }
  ],
  "notes": {
    "normal": [
      {"t": 1000, "d": 0, "l": 0},
      {"t": 1500, "d": 1, "l": 0},
      {"t": 2000, "d": 2, "l": 0},
      {"t": 2500, "d": 3, "l": 0},
      {"t": 3000, "d": 0, "l": 500},
      
      {"t": 8000, "d": 4, "l": 0},
      {"t": 8500, "d": 5, "l": 0},
      {"t": 9000, "d": 6, "l": 0},
      {"t": 9500, "d": 7, "l": 0},
      {"t": 10000, "d": 4, "l": 0},
      {"t": 10000, "d": 6, "l": 0},
      
      {"t": 12000, "d": 4, "l": 250},
      {"t": 12250, "d": 5, "l": 0},
      {"t": 12500, "d": 6, "l": 0},
      {"t": 12750, "d": 7, "l": 0}
    ]
  },
  "generatedBy": "Chart Editor"
}

This chart demonstrates:

Camera focus changes at 0ms and 8000ms
Camera zoom at 12000ms
Opponent notes (d: 0-3) from 1000-3000ms
Player notes (d: 4-7) from 8000ms onward
Various patterns: singles, holds, chords, rolls

Getting Started

Development

Modding

Game Systems

Tools

​Chart Data Format

​Chart Data Fields

​Song Note Data

​Note Fields

​Note Direction Mapping

​Note Types

​Regular Notes

​Hold Notes (Sustains)

​Special Note Kinds

​Song Events

​Event Structure

​Built-in Events

​FocusCamera

​ZoomCamera

​PlayAnimation

​SetCameraBop

​Scroll Speed

​Chart Organization

​Per-Difficulty Charts

​Shared Events

​Note Patterns

​Single Notes

​Chords

​Rolls

​Holds (Sustains)

​Jacks

​Timing Precision

​Milliseconds (Most Common)

​Ticks

​Step Alignment

​Loading Charts

​Charting Best Practices

​1. Follow the Music

​2. Difficulty Progression

​3. Playtest Extensively

​4. Use Events Effectively

​5. Balance Opponent and Player

​Example: Complete Chart

Build docs developers (and LLMs) love

Chart Data Format

Chart Data Fields

Song Note Data

Note Fields

Note Direction Mapping

Note Types

Regular Notes

Hold Notes (Sustains)

Special Note Kinds

Song Events

Event Structure

Built-in Events

FocusCamera

ZoomCamera

PlayAnimation

SetCameraBop

Scroll Speed

Chart Organization

Per-Difficulty Charts

Shared Events

Note Patterns

Single Notes

Chords

Rolls

Holds (Sustains)

Jacks

Timing Precision

Milliseconds (Most Common)

Ticks

Step Alignment

Loading Charts

Charting Best Practices

1. Follow the Music

2. Difficulty Progression

3. Playtest Extensively

4. Use Events Effectively

5. Balance Opponent and Player

Example: Complete Chart