MunosWrite mods for retro games

Munos is the language MultiNostalgia mods are written in. A mod reads the running game's memory, draws on top of its screen, and exchanges messages with other players — all from one file.

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Reference

Read and write the game

The console's RAM is an address space your script can read and write. read_u8(0x0086) is Mario's X position; write_u8 can hand him 99 lives.

Draw on top of it

Paint indexed sprites and palettes over the running frame — ghosts, menus, maps, HUDs — while the game keeps playing underneath.

Make it multiplayer

A multiplayer mod's client and server halves are two sections of the same file. send and receive carry your bytes between them.

Take the controls

Read the gamepad, capture a button before the game sees it, and pause the ROM under your own menu.

Hello, overlay

Here is a complete, working Munos mod. It draws a magenta square on top of the running game, every frame:

munos

// A 32×32 solid block of palette index 1.
var block: image = image_literal(32, 32, "AQEB…")
// Index 0 is transparent; index 1 is bright magenta.
var palette: u32[] = [0x00000000, 0x00FF00FF]

event frame(frame_num: i32) {
    draw_image(block, palette, 40, 40)
}

That's the whole program — no build config, no imports, no main, and no wrapper: a script with no server section is a client-only program that runs in the player. event frame fires once per emulator frame; draw_image paints onto the framebuffer.

Ready to write your own? Start the tutorial →