Idle Fantasy Game Developer 2D

I’m building a single-player incremental / idle fantasy game that must run smoothly both on Steam (Windows/Mac desktop build) and in a modern browser. The scope is deliberately lean: no multiplayer layers, in-app purchases, ads, or other monetisation hooks—just a polished core loop that rewards players for checking in, stepping away, and returning to meaningful progress. (2D)

Core requirements
• Desktop build prepared for Steam release (achievements and cloud save hooks ready, even if unused at launch).
• Web build that mirrors all gameplay, UI, and save functionality.
• Consistent fantasy art direction—placeholder art is fine for now if asset lists are documented.
• Solid save/load system and configurable progression variables so I can tweak balancing post-launch.
• Delivery target: fully playable, feature-locked build within one month of contract start.

Acceptance criteria at hand-off
1. A Git repo containing clean, well-commented project files (Unity, Godot, or comparable engine).
2. Steam-ready desktop installer plus WebGL/HTML5 build hosted on a test URL.
3. Short read-me covering build steps, dependency versions, and how to adjust core progression numbers.
4. A brief post-mortem video or doc walking me through scene flow, save logic, and where future content slots in.

Please include a detailed project proposal outlining engine choice, sprint schedule, and any sample incremental systems you’ve implemented before. Feel free to link playable demos; past work is appreciated but the proposal itself will guide my selection.