Milthm Web Suite

A browser-based toolset for playing and previewing Milthm rhythm game charts. The suite contains two independent players accessible from a shared landing page.

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Contents

.
├── index.html              # Landing page — select a player to open
├── style.css               # Shared stylesheet (design tokens, layout)
├── MilLune Player/         # Canvas-based chart player with scoring
└── rain player/            # WebGL-based chart player (Rain engine)

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Players

MilLune Player

A chart player built on the native MilLune engine (WebAssembly + Canvas 2D).

Features

• Loads charts packaged as .zip (with meta.json) or raw .json files
• Supports two ZIP formats: meta.json style and info.json style (with difficulty selection)
• Storyboard image loading from within the ZIP archive
• Real-time result panel with score, accuracy, grade, and judgment breakdown
• Grading system: R / Purple S / Cyan S / S / A / B / C / F
• Completion status: Rhythm of Rain / All Perfect / Full Combo / Complete / Crash
• Adjustable aspect ratio (presets + custom input)
• Theater mode (F11 or button)
• Auto-play mode

Chart ZIP requirements

File	Description
meta.json	Chart metadata (title, artist, charter, difficulty)
<audio>.ogg / .mp3	Music file referenced in meta.json
<chart>.json	Chart event data referenced in meta.json
<image> (optional)	Cover illustration referenced in meta.json

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Rain Player

A chart player built on the Rain engine, which renders via a Unity WebGL build embedded in an <iframe>.

Features

• Loads .zip charts conforming to the Milthm standard format
• Configurable gameplay parameters via a settings panel:
  • Note size, note speed, fall speed
  • Judgment offset, perfect/good windows, judgment line position
  • Master / music / SFX volume, audio offset
  • Visual toggles: particles, hit effects, judgment text, combo counter
  • Lane spacing and lane count
• Adjustable aspect ratio (presets + custom input)
• Theater mode (F11 or button)

Chart ZIP requirements

File	Description
meta.json	Chart metadata
music.ogg / music.mp3	Music file
chart/*.json	Chart event data

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Usage

Option 1 — Open directly in a browser

Note: Due to browser security restrictions on local files, opening index.html directly with file:// may fail. Use a local HTTP server instead.

Option 2 — Local HTTP server (recommended)

A minimal static file server is included:

node __serve.js

Then open http://localhost:7788 in your browser.

Any standard static server works as well:

# Python
python -m http.server 7788

# Node (npx)
npx serve .

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File Formats

meta.json (MilLune / Rain Player)

{
  "name": "Song Title",
  "music_artist": "Artist Name",
  "charter": "Charter Name",
  "difficulty_name": "Master",
  "difficulty": 12,
  "audio_file": "music.ogg",
  "image_file": "cover.png",
  "chart_file": "chart/master.json"
}

info.json (MilLune Player — multi-difficulty)

{
  "Title": "Song Title",
  "Levels": [
    {
      "Difficulty": "Master",
      "DifficultyValue": 12.0,
      "Beatmapper": "Charter Name",
      "FileMap": {
        "beatmap": "/chart/master.json",
        "song": [{ "file": "/music.ogg" }],
        "illu": "/cover.png"
      }
    }
  ]
}

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Grading Reference (MilLune Player)

Grade	Condition
R	All Perfect (large only) and score ≥ 1,010,000
Purple S	All Perfect and 1,000,000 ≤ score ≤ 1,009,999
Cyan S	Full Combo (no Bad / Miss)
S	Score ≥ 950,000
A	Score ≥ 900,000
B	Score ≥ 850,000
C	Score ≥ 800,000
F	Score < 800,000

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Browser Compatibility

Requires a modern browser with support for:

• WebAssembly
• Canvas 2D API
• ES Modules (import / export)
• File API and URL.createObjectURL

Tested on Chrome 120+ and Edge 120+. Firefox and Safari should work but are not regularly tested.

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License

This project is for personal and educational use. The Milthm game and its assets are the property of their respective owners.