NEON SATURN

This is a Android port of [Ymir](https://github.com/StrikerX3/Ymir), StrikerX3's Sega Saturn emulator.

NEON SATURN keeps Ymir's emulation core as-is and replaces the desktop frontend with a native Android
one: a setup wizard, a cover-art game library, Saturn-style touch controls, and an in-game quick actions
menu.

## Features

### Library

- Setup wizard for importing the IPL (BIOS) ROM and pointing the app at a games folder

- Games folder is read through the Storage Access Framework, so it can live anywhere on the device

- Three library views, cycled from the header: a list, NA box covers, and Japanese jewel cases

- Coverflow with perspective, reflections and snap-to-centre paging

- Cover art fetched and cached on demand, or downloaded in bulk from Settings

- Animated starfield backdrop

- Light / dark / follow-system theme, defaulting to dark

### In game

- Saturn-style touch control overlay: D-pad, analogue stick, A/B/C, X/Y/Z, L/R, Start

- Fully repositionable layout, stored separately for portrait and landscape

- Rewind and fast-forward buttons on the overlay

- Quick actions menu (back button or gamepad Select): resume, save state, load state, exit

- Physical gamepad and keyboard support via SDL, including a bundled controller database

### Emulation options

- Aspect ratio: 4:3, 16:9 or stretch
- Texture filtering: sharp (nearest) or smooth (bilinear)
- Upscaling filter: off, or 6x xBRZ
- Deinterlaced rendering of high-resolution modes
- Transparent mesh polygon rendering
- Rewind buffer (about five seconds at 60 fps), off by default
- Optional low-level CD block emulation when a CD block ROM is imported

## Usage

Install the app. The setup wizard asks for two things:

1. **IPL BIOS** — import a Saturn BIOS ROM (`.bin` or `.rom`). Required.
2. **Games folder** — choose the folder holding your disc images. Required.

A **CD Block ROM** can also be imported. It is optional, and enables low-level CD block emulation.

Once the BIOS and games folder are set, the library replaces the wizard. Tap a game to stage and launch
it. The gear icon in the header opens Settings; the icon on the left cycles between list and cover views.

Supported disc formats: **MAME CHD, BIN+CUE, IMG+CCD, MDF+MDS and ISO**. Multi-file formats need their
companion track files present in the same folder — the launcher checks for them and refuses to start if they're missing.

## Notes and limitations

**Upscaling doesn't raise the internal resolution.** Ymir's core has only a software renderer and
rasterises at Saturn-native resolution, so the upscaling filter is an edge-aware smoothing pass applied
to the finished frame. It sharpens 2D sprites and backgrounds noticeably; it cannot add 3D detail. Real
internal-resolution rendering would need a hardware renderer in the core, which does not exist yet.

**Rewind costs CPU and memory.** It saves emulator state every frame and keeps a few seconds of
LZ4-compressed deltas, so it is off by default and its on-screen button is hidden until enabled.

**Settings apply at launch.** Graphics and rewind options are read when a game starts, so changing them
takes effect the next time you launch a game.

## Credits and licence
NEON SATURN is licensed under the **GNU General Public License v3.0** — see [LICENSE](LICENSE).
- **[Ymir](https://github.com/StrikerX3/Ymir)** by StrikerX3 — the emulator core and everything this port
is built on. If you like this, support the upstream author on
[Patreon](https://www.patreon.com/StrikerX3) and join the
[Discord](https://discord.gg/NN3A7n5dzn).
- **[Kronos](https://github.com/FCare/Kronos)** / **Yabause** — the 6x xBRZ upscaling shader in
[`android/app/src/main/cpp/xbrz6x_shader.hpp`](android/app/src/main/cpp/xbrz6x_shader.hpp), used under
GPL-2.0-or-later. The original copyright notice is kept in that file.
- **[SDL3](https://github.com/libsdl-org/SDL)** — windowing, audio, input and the Android activity.

Recent changes:
• RetroAchievements support (casual mode)
• Resize the on-screen controls
• New RAM expansion cartridge slot (1MB/4MB), needed for some SNK titles
• GPU renderer: new 6x and 8x resolutions
• GPU renderer now runs on more devices, including Adreno 6xx phones
• Many GPU renderer fixes so graphics match the software renderer
• Fixed color gradation effects in the software renderer