MUGEN is the legendary free fighting-game engine, every character, stage and screen is editable text. Install it, learn the file anatomy, add fighters and stages, and make your first real edits.
Build it in our MUGEN Studio too: set up a fighter, add sprites and poses, place hitboxes and export a real fighter folder in the browser, with no install. Open the MUGEN Mod Studio →
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Reference project: download the finished code files used in this workshop: ⬇ mugen-basics-workshop-reference.zip. Every code block also has a Copy button.
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Stuck? • Character does not load → Check the .def file path matches your folder structure • WinMUGEN crashes → Make sure your SFF and AIR files are in the same folder as the DEF • No sprites appear → Open your SFF in Fighter Factory to verify the sprites exist
1
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Install MUGEN
Get the engine running with its default fighter
Active
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Goal for this step
Download MUGEN, run it, and play your first match.
1Download MUGEN 1.1 (or 1.0), the classic free engine by Elecbyte, mirrored on fan sites like the MUGEN Free For All and Mugen Archive communities.
2It is portable: unzip to a folder like C:\MUGEN\, no installer. (Windows-native; Mac/Linux users can run it via Wine.)
3Run mugen.exe: title screen! Arcade mode with the default character Kung Fu Man (KFM), the tutorial fighter the whole community learns from.
4Default controls: arrows move, A/S/D + Z/X/C are your six attack buttons (three punches, three kicks, the classic layout). F1 instantly wins a round while testing!
5Play a match. This engine has powered fan fighting games for 25 years, and every part of it is about to be yours to edit.
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Parent note: MUGEN is free closed-source software by Elecbyte, kept alive by a huge fan community. Stick to well-known community sites for downloads, and expect Windows-only tooling.
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Fill in the Blanks
+15 XP
MUGEN needs no installer, it is fully . The default tutorial fighter is Kung Fu , and the classic control layout uses attack buttons.
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Knowledge Check
+15 XP
What makes MUGEN special among game engines?
AIt is 3D
BEverything, characters, stages, menus, is plain editable files; the whole engine is a modding platform
CIt requires no files
2
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Engine Anatomy
chars, stages, data, sound, who lives where
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Goal for this step
Learn the folder structure and the files that control everything.
2The master file: data/mugen.cfg, resolution, difficulty, frame rate. Open it in Notepad (or better: Notepad++, free), it is readable text with ; comments!
3The roster file: data/select.def, the characters and stages on your select screen. Memorise this path; you will edit it constantly.
4A character folder (chars/kfm/) holds: .def (identity card), .sff (sprites), .air (animations), .cmd (commands), .cns (the brain/stats), .snd (sounds).
5Everything is text + assets. No black boxes anywhere.
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Put the Files in Order
+20 XP
Drag the character file types into the correct order, from identity to behaviour:
.cmd (input commands)
.sff (sprites)
.cns (brain / stats)
.def (identity card)
.air (animations)
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Fill in the Blanks
+15 XP
Fighters live in the folder. The select screen roster is defined in data/.def, and a character’s identity card is its file.
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Knowledge Check
+15 XP
The .def / .sff / .air / .cmd / .cns split means…
AMUGEN is disorganised
BEach concern has its own file: identity, sprites, animations, inputs, logic, separation of concerns, 1999 edition
COnly .def matters
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Add a New Fighter
Download, extract, register in select.def
Locked
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Goal for this step
Install a community character and put them on the roster.
1Grab a well-rated community character (creator sites and the big MUGEN forums host thousands, read comments, pick quality).
2Extract the character’s folder into chars/, e.g. chars/Ryu/ containing Ryu.def and friends.
3Register: open data/select.def, find the [Characters] section, add a line with the folder name (it looks for chars/Ryu/Ryu.def automatically).
4The name must match the FOLDER (and its .def name) exactly, the #1 beginner error is a typo here.
5Launch: your new fighter is on the select screen. You just modded a game engine.
data/select.def
[Characters]
;--- your roster ---
kfm
Ryu
;Ken, stages/mybeach.def <- character with a fixed stage
;randomselect <- a random slot
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If MUGEN crashes at the select screen after an edit, it is ALWAYS select.def: a typo, a missing folder, or a character made for a different MUGEN version. Comment lines out with ; to bisect.
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Fill in the Blanks
+15 XP
New fighters are extracted into chars/ and registered by adding their folder name to the ] section of select.def. Lines are commented out with the character.
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Knowledge Check
+15 XP
Adding "Ryu" to select.def makes MUGEN look for…
AAny file named Ryu anywhere
Bchars/Ryu/Ryu.def, folder and def sharing the registered name
CThe internet
4
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Add Stages & Music
Arena .def files and BGM
Locked
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Goal for this step
Install a stage, register it, and give it music.
1Stages are simpler: usually one .def + one .sff dropped straight into stages/.
2Register in select.def under [ExtraStages]: stages/mybeach.def.
3Music: open the stage’s .def, the [Music] section’s bgmusic line points at a file in sound/. Drop any .mp3 in sound/ and point bgmusic at it: custom soundtrack!
4Peek at the rest of the stage .def while you are in there: camera bounds, floor height (zoffset), parallax layers, all plain text numbers you can tweak.
3Experiment 1: life = 2000. Save, launch, fight KFM, twice the health bar!
4Experiment 2: [Size] section → xscale/yscale = 1.5, giant KFM. (Set them back after the giggle.)
5Experiment 3: [Velocity] section → walk.fwd faster. Every number in a fighting game is in files like this, balance patches ARE these edits.
chars/kfm/kfm.cns
[Data]
life = 1000 ; max health
attack = 100 ; damage dealt (%)
defence = 100 ; damage taken (%)
power = 3000 ; max super meter
[Size]
xscale = 1 ; sprite width multiplier
yscale = 1 ; sprite height multiplier
[Velocity]
walk.fwd = 2.4 ; walking speed
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Code Challenge
+20 XP
Give KFM double health and a 20% damage boost:
kfm.cns
[Data]
life =
attack =
defence = 100
💡 Hint: Health doubles from 1000; attack is a percentage where 100 is normal.
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Knowledge Check
+15 XP
Editing life = 2000 and seeing it in-game teaches the core MUGEN truth:
AMUGEN is buggy
BCharacters are DATA, every stat, move and behaviour is a number or line you can change
CHealth is cosmetic
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Roster Design & Series Roadmap
Curate a quality roster and preview the journey
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Goal for this step
Build a curated starter roster and know what comes next.
1Quality over chaos: 6-8 GOOD characters beat 100 random ones. Test each: do they feel similar in power? Do sprites match in scale/era? Curation is design.
2Arrange select.def deliberately, order and a stage per character (the "name, stages/x.def" syntax) make it feel authored.
3Try Watch mode (AI vs AI) to compare character quality quickly, balance shows fast when computers fight.
4The road ahead: Ep 2 builds a custom fighter, Ep 3 programs AI, Ep 4 designs a stage, Ep 5 assembles the complete game with screenpack and story. Your fighting game has begun.
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Fill in the Blanks
+15 XP
A curated roster of 6-8 quality fighters beats a chaotic hundred, consistent level and sprite matter. AI vs AI comparison uses mode.
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Knowledge Check
+15 XP
Why does a curated 8-fighter roster beat 100 random downloads?
ASmaller download
BCoherence: matched power, art style and quality make it feel like ONE game, not a pile of files
CMUGEN caps at 8
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What you just learned:
Installing and running MUGEN, understanding its portable no-installer structure
Engine anatomy: the chars/, stages/, data/ folders and select.def roster file
Adding community fighters and stages by registering them in select.def
Editing character stats in .cns files: life, attack, defence, scale and movement speed
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Workshop Complete!
Engine installed, files understood, fighters and stages added, first edits made, the MUGEN foundation is set. The series continues with your Custom Fighter!
