Build your own 2048.

# Build an original game inspired by 2048

You are an experienced game designer and gameplay engineer. Build a working, polished MVP from the brief below. Implement the core journeys end to end; a static mockup is not sufficient. Inspect the current environment, make sensible implementation decisions, and get started. Ask a question only if a missing answer genuinely blocks implementation.

Starting platform: Web. Explicit customized Product & audience and Tech stack requirements take precedence over this starting target.

## Product & audience
Build an original browser sliding-number puzzle called Mergefield, inspired by 2048. The main loop is sliding tiles in four directions, merging equal values, and working toward a configurable target. Use original board styling and assets. Deliver the real game rules, including no-op behavior and save/reload, rather than a grid with decorative animations.

## Design
Create an original high-contrast grid with large readable numbers, score and best-score counters, a visible target, and pause/restart/undo controls. Support arrow keys, WASD, swipe gestures, and explicit directional buttons. Tile animations should illustrate a completed engine move without determining its outcome.

## Features
1. Moves: compress each row or column in the requested direction, merge matching neighbors once per move, and compress again. A tile created by a merge cannot merge a second time in that move.

2. Tile spawning: after a move changes the board, spawn one configured tile in a seeded-random empty cell. A no-op direction must not spawn a tile, change the score, consume the random generator, or create an undo entry.

3. Outcomes: add merged values to the score, detect reaching the target, allow an explicit continue action, and detect loss only when there are no empty cells and no legal adjacent merges.

4. Session controls: pause/resume, start a fresh seeded run with confirmation, and undo the last valid move including board, score, status, and random-generator state. Show the seed so a practice run can be replayed.

5. Persistence: save the complete versioned state after each valid move and resume after reload. Keep a local best score, allow validated save export/import, and expose storage failure while the current run remains playable.

## Tech stack
Use TypeScript with a pure move reducer and injectable seeded random generator. Keep game rules, input handling, board rendering, and persistence separate. A small DOM grid is sufficient; use CSS transitions for presentation and reduced-motion support. Document tile spawn values/probabilities and target rules. Use an original implementation or preserve all required notices if deliberately adapting licensed source.

## Data & behavior
GameState {version, size, board, score, target, reachedTarget, status, rngState, seed}; UndoSnapshot with the same engine fields; BestScore; Settings. Store numeric tile values rather than CSS classes. Validate dimensions, powers-of-two values, score, and random state on import.

Acceptance checks and scope:
Test [2,2,2,2] moving left becomes [4,4,0,0] before spawning; [2,2,4,0] becomes [4,4,0,0]; a blocked move spawns nothing; and undo restores the exact next spawn. Test a full board with one available merge, target continuation, touch gestures, and reload. Exclude network leaderboards, copied artwork, and monetized competitive claims.

## Originality and assets
The named product is a reference for general workflows only. Use an original product name, visual identity, wording, layout, and assets. Do not copy proprietary code, branded logos, distinctive screens, private APIs, paid templates, or protected media. Use original or appropriately licensed sample data and assets. Build from this brief rather than scraping the reference service. Do not imply affiliation with the referenced company.

## Implementation quality
- Make every visible control work, with clear loading, success, empty, validation, and failure states. Remove controls for unimplemented features.
- Support the target platform and responsive or resizable layouts where appropriate. Use platform-appropriate accessibility semantics, labels, keyboard operation, visible focus, sufficient contrast, and reduced-motion preferences. Provide alternatives for drag-only interactions.
- Validate inputs at the relevant boundary. Treat imported or user-generated content as untrusted; render it safely. Confirm destructive actions or offer undo.
- Keep state changes reliable across navigation and reloads. Never silently lose edits. Handle persistence and network errors with an actionable message.
- Keep the scope realistic. Prioritize the complete primary journey. If a custom Features section differs from the baseline, update the data model, design, and acceptance checks to match it; explicit custom requirements take precedence over baseline assumptions.
- Provide realistic original sample content and a useful empty state. Keep sample data clearly separate from user-created data.

## Delivery and verification
1. Inspect the repository and outline the implementation in a few sentences.
2. Implement the app and connect its actual data flow. Continue until the primary journey works.
3. Run appropriate checks and test the acceptance cases above on the target platform. Verify responsive layouts and keyboard navigation when browser tools are available. For native projects, build with the available SDK and test an emulator or device when possible; report any missing native verification honestly. For games, verify the rules and gameplay loop, not only the menus.
4. Fix observed failures, then provide the runnable result, setup/run instructions, a brief explanation of what is implemented, and any specific configuration or verification limits.

This is a focused MVP. Do not add billing, AI services, or unrelated features unless explicitly requested in the brief. Start building now.