Sudoku

A touch-optimized Sudoku web application with multiple solver implementations, built with Rust compiled to WebAssembly and a TypeScript React frontend.

Features

• Multiple Sudoku grid sizes (4x4, 9x9, 16x16, 25x25)
• Three solver implementations
  • strategic solver using human-like deduction strategies (naked singles, hidden singles, X-Wing, etc.)
  • SAT-based solver using varisat for larger grids
  • backtracking solver adapted from tdoku
• Puzzle generator
  • Generates puzzles based on the strategies required to solve it
  • Multi-shot generation: generate multiple puzzles in parallel, optimizing for a grid metric
• Touch-optimized input with normal and sticky edit modes
• Puzzle import/export via clipboard
• Light and dark theme
• Offline-capable PWA with service worker support
• Published on Google Play using bubblewrap

Technical notes

Architecture

• Rust core library (sudoku-rs): generic over grid size using a compile-time Base parameter, enabling monomorphized solver code for each supported size
  • Extensive test suite: 600+ tests achieving >80% coverage
  • Performance focus:
    • benchmark suite using criterion
    • encapsulated unsafe usage for hot paths
    • verified by running test suite with miri
• WebAssembly bridge (sudoku-wasm): exposes the Rust library via wasm-bindgen with multi-threaded support through wasm-bindgen-rayon
• Web Worker offloading: expensive WASM computation runs in a web worker via comlink, keeping the UI responsive during generation and solving
  • Optimized Web Worker communication using postcard encoded binary data passed between main thread and worker using Comlink.transfer()

Languages

• Rust
  • Edition 2024
  • nightly channel enabling multi-threaded WASM
• TypeScript

Libraries

Rust:

• varisat for SAT solving, forked for WASM compatibility
  • Varisat is not actively maintained, but in 2024 was the fastest Rust-only SAT solver with a permissive license. This project targets wasm32-unknown-unknown, which complicates cross-language linking.
• rayon for parallel puzzle generation
• serde for (de)serialization in conjunction with serde-wasm-bindgen and postcard
• ts-rs for generating TypeScript types from Rust structs, enabling end-to-end type safety
• wasm-bindgen, wasm-pack and wasm-bindgen-rayon

Web:

• React with Material UI
• Jotai for state management
• Vite as build tool
• Vitest for browser testing and benchmarking

Deployment

• Caddy container serving the static Vite build
  • COOP/COEP security headers enabling SharedArrayBuffer for multi-threaded WASM
• CI/CD via GitHub Actions
• Deployed to self-managed Coolify instance running on Hetzner Cloud