tile_engine_retro

A 16-bit-console-style tile engine and shoot-em-up, written in C as a libretro core. Started in 2017 by Daniel Jiménez and Luis Navarro; resurrected in 2026.

The engine emulates the constraints of classic hardware in software: palettized 4bpp tiles, two background layers with per-scanline scroll, two sprite layers with OAM-style attributes (flips, rotation, double size), 50/50 semitransparency, palette-driven effects and fades — all composed by a span-based software renderer into an ARGB1555 framebuffer.

Asteroid Run	Crystal Cavern	Koi Pond

Two of the scenes are a horizontal shmup; the third is a top-down zen pond -- same engine, same four layers, used differently: sprite rotation becomes fish headings, per-scanline offsets become water refraction, semitransparency becomes ripples and light shafts, palette rotation becomes caustics.

Build and run

Requirements: a C compiler and RetroArch. Optional: libxmp for module music (auto-detected via pkg-config; without it the core builds silent), python3 + Pillow to regenerate the generated scene art.

On Linux Mint / Ubuntu, ./setup_linux.sh checks for the requirements, shows what it wants to install, and asks before installing. On macOS use MacPorts/Homebrew for libxmp and RetroArch.

./setup_linux.sh   # Linux only: install requirements (asks first)
make               # builds the core, the gfxtool pipeline and all assets
make run           # launches RetroArch with the core
make test          # unit tests + 30s headless gameplay + save-state
                   # round trip, all under AddressSanitizer

Controls

• D-pad / arrows — move
• A — fire (shmup) / drop food (pond)
• Start — select scene / return to the scene menu
• RetroArch hotkeys give you save states (F2/F4) and rewind for free — the core serializes its full state deterministically.

Layout

• gfx_engine.h/.c — the engine, a plain library with explicit state (gfx_context); no globals of its own
• game2.h — the game layer (structure-of-arrays entities, scene menu, scripted timelines, synthesized SFX)
• core/ — the libretro shell (input, scenes, palette effects, audio mix, save states)
• tools/gfxtool.c — manifest-driven asset pipeline (build / dump / import-scene); assets/*.mfst describe each pack
• test/ — unit tests and the headless harness (frame CRCs, PNG dumps)
• Readme — the original 2017 design document, kept current
• TODO — the living roadmap

History

The initial design document is dated 18-11-2017. Development ran through spring 2018, paused for eight years, and resumed in July 2026 — same engine, same friends.