🌊 Mizu MX 27

A small desktop operating system with a 90s soul. Windows, a Start menu, a web browser and a music player, on a kernel written from scratch. Boots from a USB stick on a real UEFI PC.

⬇️ Download · Features · Apps · Shortcuts · FAQ

Mizu (水) means water. Nami (波), the browser, is a wave.

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🚀 Try it in 3 steps

1. Download mizu-mx27-preview.img.zip from Releases and unzip it.
2. Write it to a USB stick with Rufus (choose DD image mode) or balenaEtcher.
3. Boot from the stick (usually F12, F11, F8 or Esc at power on). Secure Boot must be off.

The first start opens Mizu Setup: pick a language, check the clock, type your name. A minute later you are on the desktop. Everything you do is saved on the stick.

🖥️ Run it in a virtual machine instead

VirtualBox: new machine, type Other, version Other/Unknown (64-bit), 2 GB RAM. In System, tick Enable EFI. Attach mizu-mx27-preview.vdi to the SATA controller.

QEMU (Linux):

qemu-system-x86_64 -enable-kvm -m 2G -machine q35 \
  -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2/ovmf/OVMF_CODE.fd \
  -drive format=raw,file=mizu-mx27-preview.img \
  -device qemu-xhci -device usb-mouse -device usb-kbd \
  -device e1000e,netdev=n -netdev user,id=n -device intel-hda -device hda-output

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✨ Features

🪟 Real windows	Overlapping, draggable, resizable windows with minimise, maximise, tile and a taskbar
🏁 Start menu	Programs, Accessories and System Tools, plus Run... for anything else
🌐 Web browser	Nami Explorer: HTTP and HTTPS, stylesheets, tables, PNG, JPEG and animated GIF
🎵 Music	Plays MP3 and WAV with a seek bar
🎨 Make it yours	Colour schemes, any picture as wallpaper, desktop shortcuts
🖥️ Screen resolution	Changes live on Intel HD 2000/3000 and in QEMU, with "Keep this resolution?"
📶 Network	Wired Intel cards and phone USB tethering, DHCP or a fixed address, network icon in the tray
🌍 Languages	English, Russian, Ukrainian and Greek, switched live. Alt+Shift changes the keyboard layout
🧰 Looks after itself	Task Manager, Registry Editor, Updates, App Store, recycle bin, startup programs
🔒 Protected	Programs run in their own memory at ring 3; if the desktop crashes, it restarts by itself
🔌 Drivers	Loaded automatically for the hardware that is found

🚫 Not yet

• ❌ Installing onto a hard disk. The new installer (with its own partitions next to Windows or Linux) is being written. For now Mizu runs from the stick.
• ❌ Updates over the internet. The update channel is being set up.
• ❌ Wi-Fi. Use a cable or USB tethering from your phone.
• ❌ Secure Boot and old BIOS-only PCs.
• ❌ NTFS, exFAT, ext4. Only FAT32 disks for now.
• ⚠️ 3D graphics only on Intel HD 2000/3000 and in QEMU.

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📦 Apps

App	What it does
📁 Files	Browse drives and folders, copy, move, rename, recycle bin
📝 NoteEdit	Notepad with bold, italic and underline
🖌️ Paint	Pencil, lines, shapes, fill, opens BMP/PNG/GIF/JPEG, saves BMP
🖼️ Picture	Image viewer
🎵 Player	MP3 and WAV
🌐 Nami Explorer	Web browser
⬛ Command Prompt	The system's shell in a window: dir, mem, ping, net...
🧊 kUBIK	A spinning cube, with FPS counter
📊 Task Manager	Windows, running tasks, CPU and memory graphs, startup programs
🗂️ Registry Editor	Every setting of the system, as a tree
⬇️ Updates / 🛍️ App Store	System updates and extra programs
⚙️ Control Panel	Display, Appearance, Sound, Network, Language, Date & time, System

Extra programs on the stick: a pack of seven games and dosfetch.

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⌨️ Keyboard shortcuts

Keys	Does
Win or Ctrl+Esc	Start menu
Win+R	Run...
Alt+F4	Close the window (on an empty desktop: shut down)
Esc	Close the window in front
Ctrl+Shift+Esc	Task Manager
Alt+Shift	Switch keyboard layout
Ctrl+C / X / V	Copy, cut, paste

In the Run box, explorer opens Files and cmd opens the Command Prompt.

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❓ FAQ

How is this related to Koi-DOS?

Mizu MX 27 is built on the Koi-DOS kernel. Koi-DOS stays a DOS-like system with a command prompt; Mizu MX 27 is the desktop system grown from it. The prompt is still here, in a window.

Why is the system drive Z:?

Inherited from Koi-DOS: A: and B: were for floppies and C: was just the first free letter, so the system starts from the other end of the alphabet.

The desktop does not start.

If the desktop stops three times in a row within a few seconds, Mizu leaves you at a recovery prompt. Type desktop to try again, or log KOI.LOG to save the log and open an issue with it.

No internet.

Only wired Intel network cards and USB tethering from a phone work. Look at the network icon in the tray, or open Control Panel > Network.

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🗺️ Roadmap

1. 🔁 Safe updates: two system slots (A/B) with automatic rollback if an update does not boot
2. 💿 New installer: whole disk or only free space, next to other systems
3. ⬇️ Updates over the internet into the spare slot
4. 📁 exFAT for files over 4 GB
5. 🧩 Device Manager with live driver updates

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🛠️ For developers

Building from source

On Fedora:

sudo dnf install gcc binutils mingw64-gcc qemu-system-x86-core edk2-ovmf dosfstools mtools
make            # loader, kernel, programs, drivers, sdk/ and the desktop
./qemu.sh       # build test disks and boot in QEMU (first start runs Setup)
./release.sh    # build mizu-mx27-preview.img and .vdi

KOI_DESKTOP=0 ./qemu.sh boots to the prompt instead of the desktop. KEEP_IMAGE=1 reuses the disks.

Writing an app

An app is a module that Mizu loads and gives a table of functions (see desktop/mizu.h):

#include "mizu.h"

static const MIZU_API* mizu;

static void paint(WINDOW* window, int x, int y, int width, int height) {
    mizu->label(x + 10, y + 10, "Hello from Mizu!", mizu->color(MIZU_COLOR_TEXT));
}

static WINDOW* open(void) {
    WINDOW* window = mizu->window_new("Hello", 40, 40, 300, 200);
    if (window) window->paint = paint;
    return window;
}

static MIZU_APP me = { "Hello", 1, open, 0, 0 };

MIZU_APPLICATION(start)
static MIZU_APP* start(const MIZU_API* api) { mizu = api; return &me; }

Built with sdk/koicc -m hello.c into HELLO.APP. Plain programs use sdk/ directly.

Source layout

Folder
boot/	UEFI loader
kernel/	kernel, drivers, shell, network
drivers/	loadable drivers (.SYS)
programs/	system programs and libraries
desktop/	Mizu: desktop, Setup, apps in desktop/apps/
sdk/	kit for writing programs
include/	shared headers

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💖 Credits

Made by Koi Ayame. Kernel from Koi-DOS. Font: Terminus by Dimitar Toshkov Zhekov. MP3 decoding: minimp3 by lieff.

Built through intense pain and heartbreak. I miss you so much... Rest in peace, @nonconformie.

📄 License

MIT, see LICENSE. The font is under the SIL Open Font License 1.1; minimp3 is public domain.