This repo contains open source sample games for the Ultra Zeus fantasy console emulator written in rust.

It also contains a sample emulator written in javascript.

Ultra Zeus is a made up spec and interface for running old school games in an ultra-portable and performant way.

It's built on top of web assembly modules, which means its games run extremely fast almost anywhere, including web browsers, Unity, C, C#, Rust etc.

On most platforms, a basic emulator can be written in roughly 100 lines of code.

An Ultra Zeus game, is simply a web assembly module that exports three functions:

• void update(i32 player_1, i32 player_2). Called once per frame by the emulator with the latest player input. This is where you should update your game state.
• i32 get_screen_buffer_pointer(). returns a pointer to where in the module's memory the screen buffer is.
• (optional) i32 get_palette_buffer_pointer(). returns a pointer to where in the module's memory the current palette buffer is. If this is not exported, the default palette is used instead.

This means Ultra Zeus games can be really tiny, they are simply byte code with no extra libraries. The snake example is currently 29k.

That means you can even fit some roms in a regular link It also means you can write games in any language that can target web assembly.

Ultra Zeus graphics are inspired by 1990s home computers with low resolution pixel graphics using a customizable palette.

• The resolution is 320x240 (4:3)
• The screen buffer is 320x240 = 76,800 bytes long
• Each byte in the buffer is a palette index
• Up to 32 palette colors are supported
• Each palette color consist of 2 bytes.
  • These bytes specifies red, blue and green components, with 4 bits per channel
  • The bit arrangement is (0000rrrr, ggggbbbb)
  • This means up to 2^12 = 4096 different colors are possible
  • The 4 most significant bits of the red byte are reserved
• This means the palette buffer is 32 * 2 = 64 bytes long

See the checker_palette example for a minimal example rom using palettes.

TODO

TODO

See the ultra_snake folder for a complete example using rust to implement a complete game with input and graphics.

The samples can be built by running cargo xtask dist <game_name>.

An example/reference emulator written for web is included in index.html.

It uses simple vanilla js with no extra dependencies.