Build a Playable 2D Browser Game

PROJECT CONTEXT:
Build a small but fully functional 2D browser game. The game should run in a single web app, support keyboard controls, render visible game objects, handle collisions, track score, and include start, game over, and restart flows.

GOAL:
Create a real 2D game that can be played in the browser from start to finish, with working mechanics instead of a static mockup.

REQUIREMENTS:
- Use a browser-friendly 2D rendering approach such as HTML5 Canvas or a lightweight game loop in the app
- Implement a controllable player character or object with keyboard input
- Render enemies, obstacles, collectibles, or targets as real interactive objects
- Implement collision detection that changes score, health, or game state
- Include a visible score or progress system that updates during play
- Include a start screen or clear game start state
- Include a game over or win condition with visible feedback
- Allow the player to restart the game without refreshing the page
- Keep all core gameplay functional on desktop browser
- Organize code so game state, rendering, and input are clearly separated

CONSTRAINTS:
- Do not produce only a decorative landing page or fake game UI
- Do not rely on placeholder buttons pretending to be gameplay
- Keep scope small enough to finish in one session
- Prefer simple shapes and programmatic assets over requiring external art packs

DEFINITION OF DONE:
- The game starts and the player can control a character or object with the keyboard
- Interactive objects appear and affect gameplay through real collision logic
- Score, health, timer, or another tracked state updates correctly during play
- A win or loss condition is reachable through gameplay and clearly displayed
- The restart flow resets the full game state without needing a browser refresh
- There are no major broken loops, frozen states, or non-responsive controls

COMMON FAILURES TO AVOID:
- Building a nice-looking screen with no actual game loop or controls
- Showing score and health labels that never update from real gameplay
- Rendering objects visually but not wiring up collision behavior
- Adding a restart button that only changes text instead of resetting state
- Creating code with overlapping timers or loops that break after restart