# Credits

Ferrous Solitaire is MIT-licensed (see [LICENSE](LICENSE)). It is built on top of
the work of many open-source projects and a small handful of third-party
assets. This file lists every component that ships in the binary or in the
`assets/` directory.

---

## Code & Framework

| Component | License | Role |
|---|---|---|
| [Bevy 0.18](https://bevyengine.org/) | MIT OR Apache-2.0 | Game engine, ECS, rendering, UI |
| [kira 0.12](https://crates.io/crates/kira) | MIT OR Apache-2.0 | Audio playback (mixer, sub-tracks, looping ambient) |
| [serde](https://crates.io/crates/serde) / [serde_json](https://crates.io/crates/serde_json) | MIT OR Apache-2.0 | Serialization for save files and the sync API |
| [tokio](https://crates.io/crates/tokio) | MIT | Async runtime for the sync client and server |
| [axum 0.8](https://crates.io/crates/axum) | MIT | HTTP framework for the self-hosted sync server |
| [sqlx 0.8](https://crates.io/crates/sqlx) | MIT OR Apache-2.0 | Compile-time-checked SQLite access on the server |
| [reqwest 0.13](https://crates.io/crates/reqwest) | MIT OR Apache-2.0 | HTTP client for the sync provider |
| [jsonwebtoken 10](https://crates.io/crates/jsonwebtoken) | MIT | JWT issuance and validation |
| [bcrypt 0.19](https://crates.io/crates/bcrypt) | MIT | Password hashing on the server |
| [keyring 4](https://crates.io/crates/keyring) | MIT OR Apache-2.0 | OS keychain integration for credential storage |
| [tower-governor 0.8](https://crates.io/crates/tower-governor) | MIT | Rate limiting on `/api/auth/*` |
| [chrono](https://crates.io/crates/chrono) | MIT OR Apache-2.0 | Date / time handling |
| [uuid](https://crates.io/crates/uuid) | MIT OR Apache-2.0 | User and session identifiers |
| [thiserror](https://crates.io/crates/thiserror) | MIT OR Apache-2.0 | Error type derive |
| [rand 0.9](https://crates.io/crates/rand) | MIT OR Apache-2.0 | Seeded shuffler in `solitaire_core` |
| [png 0.17](https://crates.io/crates/png) | MIT OR Apache-2.0 | PNG encoder used by `solitaire_assetgen` |
| [ab_glyph 0.2](https://crates.io/crates/ab_glyph) | Apache-2.0 | Glyph rasterization for generated card art |

The full transitive dependency tree (several hundred crates) is captured in
`Cargo.lock` and reachable via `cargo tree`. Every crate brought in is
MIT, Apache-2.0, BSD-style, or a dual-licensed combination thereof — no
copyleft code is statically linked into the game binary.

---

## Assets

### Card artwork

| File(s) | Source | License |
|---|---|---|
| `solitaire_engine/assets/themes/default/{suit}_{rank}.svg` (52 SVGs) | [hayeah/playing-cards-assets](https://github.com/hayeah/playing-cards-assets) | MIT |
| `solitaire_engine/assets/themes/default/back.svg` | Original — Ferrous Solitaire | MIT (this project) |
| `assets/cards/faces/{RANK}{SUIT}.png` (52 PNGs) | Pre-rendered from the same `playing-cards-assets` SVGs | MIT (passed through from hayeah) |
| `assets/cards/backs/back_0.png` – `back_4.png` | Original — generated by `solitaire_assetgen::gen_art` | MIT (this project) |

The face SVGs come from Howard Yeh's `playing-cards-assets` repository, which
is itself derived from the public-domain `vector-playing-cards` Google Code
project. The art is redistributed under the MIT license — see the upstream
repository for the full notice. The files ship unmodified in the bundled
default theme; user-supplied themes can override them per-installation
through the runtime SVG theming system documented in `CARD_PLAN.md`.

The default card back is original work by this project, midnight-purple
themed to match the rest of the UI palette.

### Backgrounds

| File(s) | Source | License |
|---|---|---|
| `assets/backgrounds/bg_0.png` – `bg_4.png` | Original — generated by `solitaire_assetgen::gen_art` | MIT (this project) |

### Typography

| File | Source | License |
|---|---|---|
| `assets/fonts/main.ttf` (FiraMono-Medium) | [mozilla/Fira](https://github.com/mozilla/Fira) | SIL Open Font License 1.1 |

The OFL permits redistribution and embedding in software so long as the font
file itself is not sold standalone. The file ships unmodified.

### Audio

All six WAV files in `assets/audio/` are **original work** — there are no
third-party audio samples in this project. They are synthesized
programmatically by `solitaire_assetgen/src/bin/gen_sfx.rs`, which writes
44.1 kHz mono 16-bit PCM WAVs using a hand-rolled WAV writer (no `hound` or
`dasp` dependency). The synthesis stack is entirely additive: sine /
square waves, layered harmonics, deterministic LCG noise, AR envelopes,
and a slow LFO for the ambient track.

| File | Synthesis approach |
|---|---|
| `card_deal.wav` | Filtered LCG noise with a sweeping low-pass cutoff for a "whoosh" |
| `card_flip.wav` | High-passed LCG noise under a fast AR envelope |
| `card_place.wav` | 120 Hz sine body + filtered noise click |
| `card_invalid.wav` | Two dissonant square tones (196 Hz + 207.65 Hz) beating against each other |
| `win_fanfare.wav` | C-major arpeggio (C5 / E5 / G5 / C6) with sine + 2nd harmonic |
| `ambient_loop.wav` | 55 Hz fundamental with 2nd and 3rd harmonics, modulated by a 0.2 Hz LFO; loop length is chosen so the tone and LFO both complete an integer number of cycles for seamless looping |

Audio files are MIT-licensed alongside the rest of this project.

---

## License Summary

- **Project code:** MIT — see [LICENSE](LICENSE).
- **Card face artwork (52 SVGs from hayeah/playing-cards-assets, plus the
  pre-rendered PNGs in `assets/cards/faces/`):** MIT, redistributed
  unmodified. The original `vector-playing-cards` line art is itself
  public domain.
- **FiraMono-Medium font:** SIL Open Font License 1.1, redistributed unmodified.
- **All other assets** (backgrounds, the default `back.svg`, generated card
  backs, every audio file) are original work covered by this project's MIT
  license.

If you redistribute Ferrous Solitaire, you must ship this `CREDITS.md` and the
`LICENSE` file alongside the binary so the MIT (project + hayeah card art)
and OFL (FiraMono) notices remain visible to end users.